Iridium-catalyzed asymmetric ring-opening reactions of azabenzonorbornadiene with carboxylic acid nucleophiles

Abstract

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image)

Iridium-catalyzed asymmetric ring-opening reaction of ......-substituted azabenzonorbornadienes with various carboxylic acids has been developed. The ring-opening reaction offered trans-1,2-dihydronaphthalene products containing an allylic carboxylate moiety in moderate yields (up to 89 %) with high enantioselectivities (up to 96 %). The trans-configuration of the products was confirmed by X-ray crystallography.

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Mol Divers (2014) 18:101110 DOI 10.1007/s11030-013-9491-5

FULL-LENGTH PAPER

Iridium-catalyzed asymmetric ring-opening reactionsof azabenzonorbornadiene with carboxylic acid nucleophiles

Yuhua Long Wenling Wang Dingqiao Yang

Han Jiang Kaixuan Chen Yali Fang

Received: 4 August 2013 / Accepted: 4 November 2013 / Published online: 27 November 2013 Springer Science+Business Media Dordrecht 2013

Abstract Iridium-catalyzed asymmetric ring-opening reaction of N-substituted azabenzonorbornadienes with various carboxylic acids has been developed. The ring-opening reaction offered trans-1,2-dihydronaphthalene products containing an allylic carboxylate moiety in moderate yields (up to 89%) with high enantioselectivities (up to 96%). The trans-conguration of the products was conrmed by X-ray crystallography.

Keywords Iridium catalyst Azabenzonorbornadiene

Carboxylic acid nucleophile Asymmetry Ring-opening

reaction

Introduction

Transition metal-catalyzed asymmetric ring-opening (ARO) reaction has proven to be a great utility method in synthetic chemistry. The ARO reaction may generate multiple stereocenters in a single step, and generally produces high substituted cyclic and acyclic compounds [15]. In ARO reaction, various transition metals and nucleophiles have been explored [613]. Our previous research [1416] found that the iridium/bisphosphine complex can catalyze the ring opening of azabenzonorbornadiene and oxabenzonorbornadiene with amines and alcohols in good yield and enatioseletivity, albeit the fact that the azabenzonorbornadiene moiety was less active compared to the oxobenzonorbornadi-

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Web End =10.1007/s11030-013-9491-5 ) contains supplementary material, which is available to authorized users.

Y. Long (B) W. Wang D. Yang H. Jiang K. Chen Y. Fang

School of Chemistry and Environment, South China Normal University, Guangzhou 510006, Chinae-mail: [email protected]

ene system. To extend the synthetic utility of this methodology, herein we report the rst iridium-catalyzed asymmetric ring-opening (ARO) reaction of N-substituted azabenzonorbornadienes with various carboxylic acids acting as nucleophiles to construct trans-1,2-dihydronaphthalenes with an allylic carboxylate motif in moderate yields (up to 89%) with excellent enantioselectivities (up to 96% ee). The reaction parameters, such as ligand, halide additives, i.e., halide effect, solvents, and temperature, were discussed in detail in this paper.

We initiated our investigations using N-Ts-azabenzonorbornadiene (1a) as substrate and p-chlorobenzoic acid as nucleophile in the presence of [Ir(COD)Cl]2 (2.5mol%), (S)-BINAP (5.0mol%) in THF at 80 C, with the addition of

AgOTf (10mol%) as the scavenger of chloride ligand originating from the [Ir(COD)Cl]2. The ring-opening product 2a was obtained in good enantioselectivity (80% ee) albeit with low yield (36%) (Table 1, entry 6). Encouraged by this result, we chose different chiral ligands which are widely used in ARO reactions. In the case of (R)-(S)-PPF-PtBu2, which was identied as an ideal ligand in the rhodium-catalyzed ring opening of azabenzonorbornadienes with amines [17,18], product 2a was obtained in very poor yield and enantioselectivity (7 and 15%) (Table 1, entry 2). When (S)-tol-BINAP was used as ligand, excellent enantioselectivities (95%) were observed but with low yield (19%) (Table 1, entry 5). No acceptable results in both yield and enantioselectivity were obtained when (R)-Segphos and (R)-DTBM-Segphos were used as ligands. When we employed Bu4NI/Et3N as additives in the presence of 2.5mol% [Ir(COD)Cl]2 and 5.0mol% (S)-

BINAP, an acceptable yield together with enantioselectivity was observed (55% yield and 84% ee) (Table 1, entry 6). Based on the above ndings, we decided to use (S)-BINAP as the optimal ligand. We further found that the catalyst loading strongly affected the enantioselectivity of the reaction.

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The best yield and ee value were obtained when the loading of [Ir(COD)Cl]2 was 2.5mol%. The decrease of the catalyst loading to 1mol% led to dramatically loss of yield and ee value (33 vs 55% in yield, 56 vs 84% in ee) (Table 1, entries 8 and 9). However, further increase in the catalyst loading from 2.5 to 4.0mol% did not give positive increase in both the yield and the enantioselectivity(41% yield and 68% ee) (Table 1, entry 10).

Next, we investigated the halide effect on this ring-opening reaction (Table 2, entries 15). In the presence of NH4I/Et3N, reaction underwent smoothly and product 2a was obtained in 60% yield with 70% ee. In the case of NH4Cl/Et3N, the reaction offered high enantioselectivity but poor yield (84% ee vs 8% yield). Employed NH4F/Et3N

or NH4Br/Et3N as additives, moderate yields (54 and 57%, respectively) with low enantioselectivities (28 and 17%, respectively) were obtained. From these results, we can see iodine ion gave best results among the tested halide ions (F,

Cl, Br, I). When we changed NH4I to Bu4NI, the best yield and ee value were obtained (55% yield, 84% ee). From the temperature screening, we can see that the reaction temperature had great impact on the reaction. At room temperature (Table 2, entry 6), no ring-opening reaction occurred.When the temperature was increased from 80 to 100 C or higher, the yield was decreased from 55 to 30% or less, simultaneously, the ee value was decreased from 84 to 49% (Table 2, entries 5, 7, and 8). Another reaction parameter, solvent was testied to be crucial to this ring-opening reaction. The

Table 1 Screening of ligands and catalyst loading for the ring opening of 1a with p-chlorobenzoic acid

Entry Ligand (mol%) [Ir(COD)Cl]2 (mol%) Yield (%)b ee (%)c

1 DPPF 2.5 5 0

2 (R)-(S)-PPF-PtBu2(5.0) 2.5 7 15

3 (R)-Segphos(5.0) 2.5 44 19

4 (R)-DTBM-Segphos(5.0) 2.5 39 38

5 (S)-Tol-BINAP(5.0) 2.5 19 95

6 (S)-BINAP(5.0) 2.5 36 80

7a (S)-Tol-BINAP(5.0) 2.5 35 84

8a (S)-BINAP(5.0) 2.5 55 84

9a (S)-BINAP(2.0) 1 33 56

10a (S)-BINAP(8.0) 4 41 68

The reaction was carried out with 1a (0.1mmol) and 5.0 equiv. of p-chlorobenzoic acid (0.5mmol) in THF (1.0mL) at 80 C (oil bath temperature) in the presence of [Ir(COD)Cl]2, ligand and AgOTf (10mol%)

a Bu4NI (2.0 equiv. to 1a) and Et3N (5.0 equiv. to 1a) were used as additives

b Isolated yield

c Determined by HPLC with a Chiralcel OD-H column

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Table 2 Conditions screening for the ring opening of 1a with p-chlorobenzoic acid

Entry Additive T (C)a Solvent Yield (%)b ee (%)c

1 NH4F/Et3N 80 THF 54 282 NH4Cl/Et3N 80 THF 8 843 NH4Br/Et3N 80 THF 57 174 NH4I/Et3N 80 THF 60 705 Bu4NI/Et3N 80 THF 55 846 Bu4NI/Et3N r.t. THF n.r. 7 Bu4NI/Et3N 100 THF 30 498 Bu4NI/Et3N 120 THF Trace 9 Bu4NI/Et3N 80 THP 64 1710 Bu4NI/Et3N 80 Dioxan 78 2111 Bu4NI/Et3N 80 CH2Cl2 46 1212 Bu4NI/Et3N 80 Toluene 28 6013 Bu4NI/Et3N 80 DME Trace 14 Bu4NI/Et3N 80 CH3CN n.r.

Conditions [Ir(COD)Cl]2 (2.5mol%), ligand (5.0mol%), AgOTf (10mol%), ammonium (2 equiv. to 1a), Et3N (5 equiv. to 1a)

a Oil bath temperature

b Isolated yield

c Determined by HPLC with a Chiralcel OD-H column

optimal solvent turned out to be THF (Table 2, entry 5). The reaction in tetrahydropyran (THP) or dioxan gave product in very low ee values albeit with a higher yield (Table 2, entries 9 and 10). No ring-opening product was obtained when CH3CN was used as solvent, and only a trace amount of ring-opening product in 1,2-dimethoxy ethane (DME) (Table 2, entries 13 and 14).

On the basis of the above ndings, we constructed the optimum reaction conditions as : 2.5 mol% [Ir(COD)Cl]2, 5 mol% (S)-BINAP, 10 mol% AgOTf, 2.0 equiv. of Bu4NI and 5.0 equiv. of Et3N, 5.0 equiv. of nucleophile in THF at 80 C.

Under the optimum reaction conditions, we investigated the scope of carboxylic acids nucleophiles. When aliphatic carboxylic acids were used, the reaction gave ring-opening products in high yields (up to 89 %) but with poor enantioselectivities (Table 3, entries 15 and 16). While using aromatic carboxylic acids, the ring-opening products were obtained in moderate yields with higher enantioselectivi-ties (Table 3, entries 114). For instance, the reaction of 1a with p-nitrobenzoic acid offered much higher enantioselectivity (96% ee), but lower yield (59%), compared to acetic acid (Table 3, entries 6 and 15). Moreover, we

observed the bulkiness of chlorobenzoic acid had effect on the reaction. Compared to p-chlorobenzoic acid which gave 2a in 60 % yield and 84 % ee, m-chlorobenzoic acid and o-chlorobenzoic acid gave lower yield and enantioselectivity (47 and 35 % in yield, 61 and 53 % in ee) (Table 3, entries 1, 2, and 3). Furthermore, the electronic effect of the aromatic acid plays important role in the stereochemistry in this reaction. The substituted benzoic acid bearing electron-withdrawing groups gave higher enantioselectivities compared to those with electron-donating groups (Table 3, entries 1, 5, 6, 7, 8, and 9). For instance, pnitrobenzoic acid offered ring-opened product 2f in 96 % ee, while p-methoxylbenzoic acid gave ring-opened product 2h in 63 % ee. In addition, 1-naphthoic acid, which had higher steric hindrance, resulted in ring-opened product in moderate yield (68 %) and low enantioselectivity (41 %) (Table 3, entry 14).

Substituents on nitrogen of azabenzonorbornadiene also showed inuence on the ring-opening reaction (Table 3, entry 1; Table 4, entries 14). It was found that when N-Nsazabenzonorbornadiene (1b) and N-Bs-azabenzonorbornadiene (1c) used as substrate, both reactivity and enantioselectivity were higher than N-Boc-azabenzonorbornadiene

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Table 3 Scope of ARO of 1a with various carboxylic acids

Entry Nucleophile Product Yield (%)a ee (%)b

1 2a 60 84

2 2b 35 53

3 2c 47 61

4 2d 58 44

5 2e 54 77

6 2f 59 96

7 2g 35 79

8 2h 50 63

9 2i 22 36

10 2j 72 33

11 2k 52 19

12c 2k 35 16

13 2l 38 38

14 2m 68 41

15 2n 75 5 16 2o 89 6

Conditions [Ir(COD)Cl]2 (2.5 mol%), S-BINAP (5.0 mol%), AgOTf (10 mol%), Bu4NI (2 equiv. to 1a), nucleophiles (5 equiv. to 1a) and Et3N (5 equiv. to 1a), 80C (oil bath)

a Isolated yield

b Determined by HPLC with a Chiralcel OD-H column

c Nucleophile was 2 equiv. to 1a(1d) but lower than N-Ts-azabenzonorbornadiene (1a) as substrate. However, the N-Ac-azabenzonorbornadiene (1e) cannot undergo ring opening under the current condi-

tion. The results disclosed that a suitable electronic effect and steric effect on the nitrogen are important for this reaction.

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Table 4 Ring opening of N-substituted azabenzonorbornadiene 1b, 1c, 1d , and 1e with p-chlorobenzoic acid

Entry R1 Nucleophile Product Yield (%)a ee (%)b

1 Ns 3a 50 43

2 Bs 4a 56 59

3 BOC 5a 9 19

4 Ac 6a n.r.

Conditions [Ir(COD)Cl]2 (2.5 mol%), S-BINAP (5.0 mol%), AgOTf (10 mol%), Bu4NI (20 mol%) nucleophiles (5 equiv. to 1) and Et3N (5 equiv. to 1), 80C (oil bath)

a Isolated yield

b Determined by HPLC with a Chiralcel OD-H column

Fig. 1 ORTEP representation of 2e

The absolute conguration of 2e was assigned as (1R, 2R) which was conrmed by X-ray crystallography (Fig. 1).

In conclusion, we have successfully developed an iridiumcatalyzed ARO reactions of N-substituted azabenzonorbornadienes with various carboxylic acids, which afforded the corresponding products in moderate yields (up to 89 %) with good enantioselectivities (up to 96 % ee) under mild conditions for the rst time. It was observed that the nature of the chiral ligand has a signicant impact on the reactivity of the catalyst and the enantioselectivitiy in the ring-opening reaction. Our results further revealed that both the substituted groups on nitrogen of the N-substituted azabenzonorbornadienes and the electronic effect of nucleophiles were found to have remarkable impact on the yield and enantioselectivity of the ring-opening reaction.

Experimental section

General information

All asks were ame-dried under a stream of nitrogen and cooled before use. All commercially available chemicals were used as-received without further purication unless otherwise indicated. All solvents were puried according to standard procedures. Solvents and solutions were transferred with syringes using standard inert atmosphere techniques. All

1H and 13C NMR spectra were recorded on a Varian INOVA NMR spectrometer at 400 and 100 MHz, respectively, with CDCl3 or (CD3)2CO as deuterated solvents and internal stan-

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dards ( 7.26 ppm or 2.05 ppm) for 1H NMR and ( 77.16 ppm or 29.84 ppm and 206.26 ppm) for 13C NMR. Spec

tral features are tabulated in the following order: chemical shift (, ppm); multiplicity (s-singlet, d-doublet, t-triplet, qquadruplet, m-multiplet, br-broad); coupling constants (J, Hz), number of protons. N-Substituted azabenzonorbornadienes 1a, 1b, 1c, 1d, and 1e were prepared according to the literature [8].

General procedure for the ARO reactions of N-substituted azabenzonorbornadienes with carboxylic acids

A 5-mL round-bottom ask was ame-dried under a stream of nitrogen, tted with a reux condenser, and cooled to room temperature. [Ir(COD)Cl]2 (1.7 mg, 2.5 mol%) and (S)-BINAP (3.1 mg, 5.0 mol%) were added simultaneously followed by the addition of anhydrous tetrahydrofuran (1.0 mL). After stirring at room temperature for 30 min, silver triuoromethanesulfonate (2.6 mg, 10.0 mol%), Bu4NI (2 equiv.), and substrate 1 (0.10 mmol, 1 equiv.)

were added, the ask was placed in an pre-heated (80 C) oil bath, and the resulting mixture was stirred and heated to reux. Once reux has been reached, a carboxylic acid (5 equiv.) and Et3N (5 equiv.) were added. The reaction was heated further until the reaction was completed as indicated by TLC. The solvent was removed in vacuum and the resulting residue was puried by column chromatography on silica gel (ethyl acetate/petroleum ether as eluent) to give the target product.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-4-chlorobenzoate 2a

2a was obtained as a white solid (27.2 mg, 60 %), mp 185 186 C; []20D= 148.6 (c=1.00, CHCl3); IR(KBr, cm1)

3289(m), 3053(s), 2985(m), 2930(w), 2851(m), 1715(m), 1594(m), 1485(w), 1423(s), 1401(w), 1326(m), 1264(s), 1158(s), 1113(w), 1094(m), 895(s), 741(s), 665(w), 568(w);

1H NMR (400 MHz, CDCl3) 7.72 (d, J = 8.8 Hz, 2H),

7.66 (d, J = 8.4 Hz, 2H), 7.37 (d, J = 7.6 Hz, 1H),

7.33 (d, J = 8.4 Hz, 2H), 7.237.30 (m, 2H), 7.13 (dd,

J = 1.6, 7.2 Hz, 1H), 7.03 (d, J = 8.0 Hz, 2H), 6.59 (dd,

J = 1.2, 9.6 Hz, 1H), 5.93 (dd, J = 3.2, 9.6 Hz, 1H), 5.82

(ddd, J = 1.6, 3.2, 9.2 Hz, 1H), 4.96 (t, J = 8.8 Hz, 1H),

4.91 (t, J = 8.8 Hz, 1H), 2.24 (s, 3H); 13C NMR (100 MHz,

CDCl3) 165.3, 143.2, 139.6, 137.9, 133.1, 132.0, 131.2, 130.3, 129.5, 128.7, 128.7, 128.5, 127.7, 127.2, 127.1, 126.7, 125.3, 72.4, 56.8, 21.5; MS (ESI) calcd for C24H20ClNO4S (M+) 453.08, found 476.31 (M+Na)+. Anal. calcd for

C24H20ClNO4S: C, 63.50; H, 4.44; N, 3.09; S, 7.06. Found: C, 63.51; H, 4.46; N, 3.08; S, 7.07.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-2-chlorobenzoate (2b)

2b was obtained as a white solid (15.9 mg, 35 %), mp 148 149 C; []20D= 132.6 (c=1.00, CHCl3); IR(KBr, cm1)

3299(s), 3064(w), 2913(s), 2851(m), 1709(s), 1591(m), 1452(w), 1432(m), 1326(s), 1287(m), 1248(s), 1156(s), 1122(m), 1049(m), 956(m), 808(w), 780(w), 747(m), 666(m), 568(m), 545(m); 1HNMR(400 MHz, CDCl3) 7.71 (d, J = 7.6Hz, 2H), 7.66 (d, J = 7.6 Hz, 1H), 7.38 (s, 2H),

7.217.26 (m, 4H), 7.10 (d, J = 6.8Hz, 3H), 6.61 (d, J =

9.6 Hz, 1H), 6.02 (d, J = 8.0 Hz, 1H), 5.73 (d, J = 4.4Hz,

1H), 4.98 (d, J = 7.2 Hz, 1H), 4.87 (t, J = 7.6Hz, 1H),

2.27 (s, 3H); 13C NMR (100 MHz, CDCl3) 164.7, 143.3, 137.8, 134.2, 132.8, 132.8, 131.9, 131.9, 131.1, 130.8, 129.6, 128.8, 128.8, 128.7, 127.5, 127.2, 126.9, 126.4, 124.6, 72.2,55.8, 21.5; MS (ESI) calcd for C24H20ClNO4S (M+) 453.08, found 476.17 (M+Na)+. Anal. calcd for C24H20ClNO4S: C,63.50; H, 4.44; N, 3.09; S, 7.06. Found: C, 63.48; H, 4.45; N, 3.09; S, 7.06.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-3-chlorobenzoate (2c)

2c was obtained as a white solid (21.3 mg, 47 %), mp 144145

C; []20D = 36.6 (c = 1.00, CHCl3); IR (KBr, cm1)

3366(m), 3047(s), 2980(m), 2913(w), 1720(s), 1600(m), 1572(m), 1424(s), 1329(m), 1264(s), 1158(m), 1127(w), 1088(w), 1071(w), 892(m), 741(s), 665(w), 570(w); 1H

NMR (400MHz, CDCl3) 7.70 (s, 2H), 7.66 (d, J = 7.6Hz,

2H), 7.51(d, J = 7.6Hz, 1H), 7.38(d, J = 6.8Hz, 1H),

7.267.33 (m, 3H), 7.13 (d, J = 6.8Hz, 1H), 7.02 (d, J =

7.6Hz, 2H), 6.59 (d, J = 9.6Hz, 1H), 5.92 (d, J = 9.6Hz,

1H), 5.81 (d, J = 8.8Hz, 1H), 5.02 (s, 1H), 4.91(t, J =

9.2 Hz, 1H), 2.22(s,3H); 13C NMR (100 MHz, CDCl3) 165.0, 143.2, 138.0, 134.3, 133.1, 133.1, 132.0, 131.0, 130.4, 129.8, 129.5, 129.5, 128.7, 127.9, 127.2, 127.1, 126.7, 125.1, 72.7, 56.7, 21.4; MS (ESI) calcd for C24H20ClNO4S (M+) 453.08, found 476.16 (M+Na)+. Anal. calcd for

C24H20ClNO4S: C, 63.50; H, 4.44; N, 3.09; S, 7.06. Found: C, 63.50; H, 4.45; N, 3.08; S, 7.04.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-4-uorobenzoate (2d)

2d was obtained as a white solid (26.7 mg, 58 %), mp 178 179C; []20D = 90.9 (c = 1.00, CHCl3); IR(KBr, cm1)

3356(m), 3053(s), 2985(m), 2924(w), 1715(m), 1600(m), 1547(w), 1505(w), 1418(s), 1323(m), 1264(s), 1155(m), 1110(w), 1085(w), 892(s), 850(w), 735(s), 567(w); 1H NMR (400 MHz, CDCl3) 7.81 (t, J = 6.4Hz, 2H), 7.67 (d,

J = 7.6Hz, 2H), 7.247.34 (m, 3H), 7.12 (d, J = 6.8Hz,

1H), 7.04 (d, J = 8.4Hz, 4H), 6.59 (d, J = 10 Hz, 1H),

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Mol Divers (2014) 18:101110 107

5.93 (d, J = 8.8Hz, 1H), 5.78 (d, J = 8.4Hz, 1H), 5.01 (d,

J = 8.0 Hz, 1H), 4.90 (t, J = 8.8Hz, 1H), 2.24 (s, 3H); 13C

NMR (100MHz, CDCl3) 165.2, 143.2, 137.9, 133.1, 132.5, 132.4, 132.0, 130.3, 129.6, 128.7, 128.7, 127.2, 127.1, 126.8, 125.3, 115.4, 115.2, 72.3, 56.6, 21.5; HRMS (ESI) calcd for C24H20FNO4S [M-H] 436.1024, found 436.1030.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-4-bromobenzoate (2e)

2e was obtained as a white solid (26.8 mg, 54 %), mp 190 191 C; []20D = 85.7 (c = 1.00, CHCl3); IR(KBr, cm1)

3367(m), 3053(s), 2986(s), 2919(s), 2851(m), 2302(w), 1717(s), 1592(m), 1530(m), 1482(w), 1421(s), 1264(s), 1161(m), 1116(w), 1099(w), 1068(w), 1015(m), 892(s), 733(s), 571(w); 1H NMR (400 MHz, CDCl3) 7.65 (t, J =

6.8Hz, 4H), 7.49 (d, J = 8.0 Hz, 2H), 7.37 (d, J = 6.8Hz,

1H), 7.237.31 (m, 2H), 7.13 (d, J = 6.8Hz, 1H), 7.02

(d, J = 7.6Hz, 2H), 6.58 (d, J = 9.6Hz, 1H), 5.92

(dd, J = 9.6, 2.4Hz, 1H), 5.80 (d, J = 8.4Hz, 1H), 4.97 (d,

J = 8.4Hz, 1H), 4.91 (t, J = 8.8Hz, 1H), 2.24(s, 3H); 13C

NMR (100 MHz, CDCl3) 165.4, 143.2, 138.0, 133.1, 132.0, 131.5, 131.3, 130.3, 129.5, 128.7, 128.7, 128.3, 128.2, 127.2, 127.1, 126.8, 126.7, 125.3, 72.5, 56.8, 21.5; MS (ESI) calcd for C24H20BrNO4S (M+) 497.03, found 520.00 (M+Na)+.

Anal. calcd for C24H20BrNO4S: C, 57.84; H, 4.04; N, 2.81;

S, 6.43. Found: C, 57.90; H, 4.04; N, 2.80; S, 6.43.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-4-nitrobenzoate (2f)

2f was obtained as a white solid (27.4 mg, 59 %), mp 176178 C; []20D = 176.2 (c = 1.00, CHCl3); IR

(KBr, cm1) 3367(s), 3053(s), 2986(m), 2924(w), 2857(w), 2302(m), 1726(w), 1600(m), 1530(m), 1418(s), 1307(m), 1342(m), 1264(s), 1158(m), 1116(w), 1102(w), 1015(w), 959(w), 892(m), 744(s), 567(w); 1H NMR (400 MHz, CDCl3) 8.21 (d, J = 9.2 Hz, 2H), 8.01 (d, J = 8.8Hz,

2H), 7.71 (d, J = 8.4Hz, 2H), 7.30 (td, J = 1.2, 7.2Hz,

1H), 7.22(td, J = 1.2, 7.6Hz, 1H), 7.17 (d, J = 8.8Hz,

2H), 7.13 (d, J = 8.0 Hz, 2H), 6.64 (d, J = 10 Hz, 1H), 6.00

(dd, J= 3.6, 10.0Hz, 1H), 5.82 (ddd, J = 1.2, 3.6, 8.0 Hz,

1H), 4.93 (t, J = 8.4Hz, 1H), 4.87 (t, J = 8.4Hz, 1H),

2.27 (s, 3H); 13C NMR (100MHz, CDCl3) 164.2, 150.5, 143.4, 137.9, 134.8, 132.6, 131.8, 130.9, 129.7, 129.0, 128.8, 128.8, 127.3, 127.1, 126.8, 124.4, 123.3, 72.9, 56.1, 21.5; MS (ESI) calcd for C24H20N2O6S (M+) 464.10, found 487.29 (M+Na)+. Anal. calcd for C24H20N2O6S: C, 62.06; H, 4.34;

N, 6.03; S, 6.90. Found: C, 62.04; H, 4.33; N, 6.04; S,6.89.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-4-(triuoromethyl)benzoate (2g)

2g was obtained as a white solid (17.0 mg, 35 %), mp 175 177 C; []20D = 80.6 (c = 1.00, CHCl3); 1H NMR

(400 MHz, CDCl3) 7.92 (d, J = 8 Hz, 2H), 7.67 (d,

J = 7.6Hz, 2H), 7.63 (d, J = 8.0 Hz, 2H), 7.237.32 (m,

3H), 7.14 (d, J = 7.2 Hz, 1H), 7.04 (d, J = 8.0 Hz, 2H), 6.61

(d, J = 9.6Hz, 1H), 5.95 (d, J = 9.6Hz, 1H), 5.83 (d, J =

8.4 Hz, 1H), 4.99 (d, J = 8.4Hz, 1H), 4.93 (t, J = 8.8Hz,

1H), 2.21 (s, 3H); 13C NMR (100MHz, CDCl3) 164.9, 143.3, 138.0, 132.9, 132.5, 132.0, 130.6, 130.2, 129.6, 128.8, 128.8, 127.2, 127.1, 126.8, 125.2, 125.1, 125.1, 125.0, 72.8,56.6, 21.3; HRMS (ESI) Calcd for C25H20F3NO4S [M-H] 486.0992, found 486.1004.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-4-methoxybenzoate (2h)

2h was obtained as a white solid (22.5 mg, 50 %), mp 177178C; []20D = 134.3 (c = 1.00, CHCl3);

IR (KBr, cm1) 3692(m), 3048(s), 2980(m), 2302(m), 1706(m), 1602(m), 1527(s), 1493(s), 1418(m), 1261(s), 1164(w), 1102(w), 984(w), 892(m), 741(s), 565(w); 1H

NMR (400 MHz, CDCl3) 7.72 (d, J = 8.4 Hz, 2H), 7.65

(d, J = 7.6 Hz, 2H), 7.42 (d, J = 6.4 Hz, 1H), 7.26 (t, J =

6.0 Hz, 2H), 7.11 (d, J = 6.4 Hz, 1H), 6.99 (d, J = 7.6Hz,

2H), 6.82 (d, J = 8.4 Hz, 2H), 6.56 (d, J = 9.6 Hz, 1H),

5.92 (d, J = 8.4 Hz, 1H), 5.77 (d, J = 9.2 Hz, 1H), 5.13

(d, J = 7.6 Hz, 1H), 4.89 (t, J = 8.4 Hz, 1H), 2.86 (s, 3H),

2.20 (s, 3H); 13C NMR (100 MHz, CDCl3) 166.0, 163.5, 143.0, 137.9, 133.4, 132.1, 131.9, 130.0, 129.5, 128.6, 127.3, 126.9, 126.8, 125.9, 121.7, 113.4, 105.0, 71.9, 56.9, 55.4,21.4; MS (ESI) calcd for C25H23NO5S (M+) 449.13, found 472.24 (M+Na)+. Anal. calcd for C25H23NO5S: C, 66.80;

H, 5.16; N, 3.12; S, 7.13. Found: C, 66.81; H, 5.18; N, 3.11; S, 7.14.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-4-methylbenzoate (2i)

2i was obtained as a white solid (9.5 mg, 22 %), mp 198 199 C; []20D = 33.3 (c = 1.00, CHCl3); IR (KBr, cm1)

3356(w), 3053(s), 2985(s), 2913(w), 2846(m), 1703(m), 1605(m), 1544(w), 1421(s), 1323(w), 1261(s), 1160(m), 1110(w), 1066(w), 1018(w), 895(s), 747(s), 571(w); 1H

NMR (400 MHz, CDCl3) 7.63 (t, J = 2.4 Hz, 4H), 7.40

(d, J = 6.8 Hz, 1H), 7.237.26 (m, 2H), 7.087.13 (m, 3H),

6.95 (d, J = 8.0 Hz, 2H), 6.54 (d, J = 9.6 Hz, 1H), 5.90

(dd, J = 2.8, 9.6 Hz, 1H), 5.75 (d, J = 9.2 Hz, 1H), 4.99 (d,

J = 8.0 Hz, 1H), 4.86 (t, J = 8.4 Hz, 1H), 2.38 (s, 3H), 2.15

(s, 3H); 13C NMR (100 MHz, CDCl3) 166.3, 143.8, 143.0,

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108 Mol Divers (2014) 18:101110

137.8, 133.3, 132.0, 130.1, 129.8, 129.5, 128.8, 128.6, 127.3, 126.9, 126.7, 126.6, 126.5, 125.7, 71.9, 56.8, 21.6, 21.4; MS (ESI) calcd for C25H23NO4S (M+) 433.13, found 456.23 (M+Na)+. Anal. calcd for C25H23NO4S: C, 69.26; H, 5.35;

N, 3.23; S, 7.40. Found: C, 69.25; H, 5.34; N, 3.23; S, 7.38.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-3-methoxybenzoate (2j)

2j was obtained as a white solid (32.3 mg, 72 %), mp 111112 C; []20D = 86.7 (c = 1.00, CHCl3); IR

(KBr, cm1) 3283(s), 3059(m), 2919(m), 2840(w), 1712(s), 1597(s), 1482(m), 1452(s), 1432(m), 1326(s), 1273(m), 1228(m), 1183(w), 1158(s), 1096(m), 1071(m), 1040(m), 987(w), 920(w), 811(m), 786(m), 749(s), 702(w), 666(s), 568(s), 545(m); 1H NMR (400 MHz, CDCl3) 7.65 (d,

J = 7.6 Hz, 2H), 7.38 (t, J = 6.4 Hz, 2H), 7.31 (s,

1H), 7.26 (t, J = 8.8 Hz, 3H), 7.077.12 (m, 2H), 7.00

(d, J = 7.6 Hz, 2H), 6.57 (d, J = 10.0 Hz, 1H), 5.93

(d, J = 7.6 Hz, 1H), 5.79 (d, J = 8.8 Hz, 1H), 5.10 (s,

1H), 4.91 (t, J = 4.8 Hz, 1H), 3.82 (s, 3H), 2.21 (s, 3H); 13C

NMR (100 MHz, CDCl3) 166.1, 159.3, 143.2, 137.9, 133.2, 132.1, 130.6, 130.2, 129.5, 129.1, 128.6, 128.6, 127.2, 127.0, 126.7, 125.5, 122.2, 119.6, 114.2, 72.3, 56.7, 55.4, 21.4; MS (ESI) calcd for C25H23NO5S (M+) 449.13, found 472.26 (M+Na)+. Anal. calcd for C25H23NO5S: C, 66.80; H, 5.16;

N, 3.12; S, 7.13. Found: C, 66.89; H, 5.15; N, 3.12; S, 7.15.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-2-methylbenzoate (2k)

2k was obtained as a white solid (22.5 mg, 52 %), mp 147 148 C; []20D = 28.9 (c = 1.00, CHCl3); IR (KBr, cm1)

3367(m), 3053(s), 2986(m), 2924(w), 2851(w), 2302(m), 1717(s), 1600(m), 1457(m), 1421(s), 1337(w), 1320(w), 1264(s), 1158(m), 1141(w), 1094(w), 1079(m), 962(w), 892(m), 744(s), 568(w), 548(w); 1H NMR (400 MHz, CDCl3) 7.67 (d, J = 7.6 Hz, 3H), 7.38 (t, J = 7.6 Hz,

1H), 7.31 (d, J = 7.2 Hz, 1H), 7.27 (d, J = 6.8 Hz, 1H),

7.23 (d, J = 7.2 Hz, 1H), 7.17 (t, J = 6.0 Hz, 2H),

7.12 (d, J = 7.2 Hz, 1H), 7.02 (d, J = 8.0 Hz, 2H),

6.59 (d, J = 9.6 Hz, 1H), 5.98 (d, J = 9.6 Hz, 1H),

5.74 (d, J = 6.4 Hz, 1H), 5.06 (d, J = 8.0 Hz, 1H),

4.86 (t, J = 8.0 Hz, 1H), 2.42 (s,3H), 2.23 (s, 3H); 13C

NMR (100 MHz, CDCl3) 166.8, 143.2, 140.7, 137.8, 133.1, 132.3, 132.0, 131.7, 131.1, 130.4, 129.5, 128.7, 128.6, 128.3, 127.4, 127.1, 126.9, 126.7, 125.6, 125.4, 71.5, 56.4, 22.1,21.5; MS (ESI) calcd for C25H23NO4S (M+) 433.13, found 456.09 (M+Na)+. Anal. calcd for C25H23NO4S: C, 69.26;

H, 5.35; N, 3.23; S, 7.40. Found: C, 69.01; H, 5.33; N, 3.23;

S, 7.38.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-benzoate (2l)

2l was obtained as a white solid (15.9 mg, 38 %), mp 185187 C; []20D = 57.8 (c = 1.00, CHCl3);

IR (KBr, cm1) 3288(w), 3059(w), 2919(s), 2846(m), 1712(m), 1594(w), 1583(w), 1491(w), 1452(m), 1337(s), 1264(s), 1155(s), 1091(m), 1110(m), 1021(w), 965(w), 923(w), 848(w), 811(w), 789(m), 749(w), 691(m), 671(m), 699(m), 545(m); 1H NMR (400 MHz, CDCl3) 7.79 (d, J = 7.2 Hz, 2H), 7.66 (d, J = 8.4 Hz, 2H), 7.54 (t,

J = 7.6 Hz, 1H), 7.37 (q, J = 8.0 Hz, 3H), 7.247.31 (m,

2H), 7.13 (d, J = 7.2 Hz, 1H), 6.99 (d, J = 8.0 Hz, 2H),

6.58 (d, J = 9.6 Hz, 1H), 5.94 (dd, J = 3.2, 9.6 Hz, 1H),

5.80 (ddd, J = 1.6, 3.2, 8.8 Hz, 1H), 5.04 (d, J = 8.0 Hz,

1H), 4.90 (t, J = 8.8 Hz, 1H), 2.20 (s, 3H); 13C NMR

(100 MHz, CDCl3) 166.2, 143.1, 137.8, 133.2, 133.1, 132.0, 130.2, 129.8, 129.6, 129.3, 128.7, 128.6, 128.1, 127.3, 127.0, 126.7, 125.5, 72.1, 56.7, 21.5; MS (ESI) calcd for C24H21NO4S (M+) 419.12, found 442.15 (M+Na)+. Anal.

calcd for C24H21NO4S: C, 68.72; H, 5.05; N, 3.34; S, 7.64. Found: C, 68.79; H, 5.05; N, 3.33; S, 7.66.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-1-naphthoate (2m)

2m was obtained as a white solid (31.9 mg, 68 %), mp 167 168 C; []20D = 22.8 (c = 1.00, CHCl3); IR (KBr, cm1)

3283(s), 3053(m), 2924(s), 2851(m), 1709(s), 1591(m), 1572(w), 1508(m), 1452(m), 1329(s), 1278(m), 1242(s), 1191(s), 1158(s), 1127(s), 1090(m), 1071(m), 1001(m), 923(m), 811(m), 778(s), 735(m), 699(m), 665(s), 565(s), 542(m); 1H NMR (400 MHz, CDCl3) 8.80 (d, J = 8.0 Hz,

1H), 8.00 (t, J = 8.0Hz, 1H), 7.95 (d, J = 6.8 Hz, 1H),

7.87 (d, J = 7.2 Hz, 1H), 7.63 (d, J = 7.6 Hz, 2H), 7.55

(s, 2H), 7.38 (t, J = 8.0 Hz, 2H), 7.257.30 (m, 2H), 7.14

(d, J = 6.8 Hz, 1H), 6.80 (d, J = 7.6 Hz, 2H), 6.62 (d,

J = 9.6 Hz, 1H), 6.05 (dd, J = 2.4 Hz, 9.6 Hz, 1H),

5.88 (d, J = 8.0 Hz, 1H), 5.13 (d, J = 8.0 Hz, 1H), 4.95

(d, J = 8.4 Hz, 1H), 2.02 (s, 3H); 13C NMR (100 MHz,

CDCl3) 166.7, 143.1, 137.8, 133.8, 133.7, 133.2, 132.0, 131.4, 130.9, 130.5, 130.5, 129.4, 128.7, 128.7, 128.5, 127.9, 127.5, 127.1, 126.7, 126.2, 125.8, 125.7, 125.4, 124.3, 71.9,56.4, 21.2; MS (ESI) calcd for C28H23NO4S (M+) 469.13, found 492.22 (M+Na)+. Anal. calcd for C28H23NO4S: C,71.62; H, 4.94; N, 2.98; S, 6.83. Found: C, 71.57; H, 4.95; N, 2.98; S, 6.82.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-acetate (2n)

2n was obtained as a white solid (26.8 mg, 75 %), mp 135137 C; []20D = 13.6 (c = 1.00, CHCl3); IR

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Mol Divers (2014) 18:101110 109

(KBr, cm1) 3260(s), 3064(w), 2918(s), 2857(w), 1734(s), 1650(w), 1597(m), 1569(w), 1490(w), 1452(m), 1432(s), 1371(m), 1326(s), 1287(w), 1239(s), 1155(s), 1124(w), 1093(s), 1071(m), 1018(m), 968(w), 931(w), 805(m), 749(m), 705(w), 671(s), 565(s), 548(s); 1H NMR (400 MHz, CDCl3) 7.77 (d, J = 8.0 Hz, 2H), 7.32 (d, J = 8.0 Hz,

2H), 7.25 (t, J = 5.6 Hz, 1H), 7.16 (q, J = 8.4 Hz, 2H),

7.09 (d, J= 7.2 Hz, 1H), 6.54 (d, J = 9.6 Hz, 1H), 5.88

(dd, J = 4.0, 10.0 Hz, 1H), 5.46 (dd, J = 4.0, 8.0 Hz, 1H),

4.92 (d, J = 8.4 Hz, 1H), 4.71 (t, J = 8.0 Hz, 1H), 2.44

(s, 3H), 1.78 (s, 3H); 13C NMR (100 MHz, CDCl3) 170.6, 143.5, 138.2, 132.8, 131.9, 130.4, 129.7, 128.7, 128.5, 127.4, 127.1, 127.1, 125.0, 71.0, 55.7, 21.5, 20.7; MS (ESI) calcd for C19H19NO4S (M+) 357.10, found 380.19 (M+Na)+. Anal.

calcd for C19H19NO4S: C, 63.85; H, 5.36; N, 3.92; S, 8.97.

Found: C, 63.66; H, 5.35; N, 3.92; S, 8.99.

(1R,2R)-1-(4-Methylphenylsulfonamido)-1,2-dihydronaphthalen-2-yl-pivalate (2o)

2o was obtained as a white solid (35.5 mg, 89 %), mp 171172 C; []20D = 16.9 (c = 1.00, CHCl3); IR

(KBr, cm1) 3272(s), 3053(m), 2969(s), 2919(s), 2851(m), 1714(s), 1647(s), 1600(s), 1477(m), 1452(m), 1393(w), 1331(s), 1278(m), 1155(s), 1096(m), 1068(w), 970(w), 926(w), 811(m), 791(m), 668(s), 568(s); 1H NMR (400 MHz, CDCl3) 7.75 (d, J = 8.0 Hz, 2H), 7.30 (d, J = 7.6 Hz,

2H), 7.21 (t, J = 7.6 Hz, 1H), 7.07 (d, J = 7.6 Hz,

2H), 6.85 (d, J = 7.2 Hz, 1H), 6.56 (d, J = 9.6 Hz,

1H), 5.93 (dd, J = 3.6, 9.6 Hz, 1H), 5.36 (s, 1H), 4.87

(d, J = 8.0 Hz, 1H), 4.69 (t, J = 7.2 Hz, 1H), 2.44 (s, 3H),

1.07 (s, 9H); 13C NMR (100 MHz, CDCl3) 178.0, 143.5, 138.2, 132.6, 131.8, 130.6, 129.8, 128.7, 128.4, 127.4, 127.1, 127.0, 124.8, 70.1, 55.1, 38.7, 26.9, 21.6; MS (ESI) calcd for C22H25NO4S (M+) 399.15, found 422.31 (M+Na)+. Anal.

calcd for C22H25NO4S: C, 66.14; H, 6.31; N, 3.51; S, 8.03.

Found: C, 65.94; H, 6.30; N, 3.52; S, 8.04.

(1R,2R)-1-(4-Nitrophenylsulfonamido)-1,2-dihydronaphthalen-2-yl-4-chlorobenzoate (3a)

3a was obtained as a white solid (24.2 mg, 50 %), mp 188189 C; []20D = 82.0 (c = 1.00, CHCl3); IR

(KBr, cm1) 3277(m), 3109(m), 3064(w), 2924(s), 2851(s), 1715(m), 1658(m), 1602(m), 1591(m), 1530(s), 1460(m), 1398(w), 1351(s), 1312(m), 1267(m), 1161(s), 1091(s), 1012(m), 929(w), 853(m), 800(w), 777(m), 735(s), 685(m), 612(s), 542(s), 467(w); 1H NMR (400 MHz, CDCl3) 8.02 (d, J= 6.4 Hz, 2H), 7.94 (d, J = 7.2 Hz, 2H), 7.67

(d, J = 6.4 Hz, 2H), 7.48 (s, 1H), 7.32 (m 5H), 7.17 (s,

1H), 6.60 (d, J = 9.2 Hz, 1H), 5.87 (t, J = 8.0 Hz, 2H),

4.99 (t, J = 8.4 Hz, 1H); 13C NMR (100 MHz, CDCl3)

165.2, 148.9, 147.8, 133.4, 133.0, 131.5, 131.0, 131.0, 129.7,

128.8, 128.5, 128.2, 127.9, 127.0, 126.8, 125.7, 124.4, 73.1,56.6; MS (ESI) calcd for C23H17ClN2O6S (M+) 484.05, found 507.14 (M+Na)+. Anal. calcd for C23H17ClN2O6S:

C, 56.97; H, 3.53; N, 5.78; S, 6.61. Found: C, 56.81; H, 3.54; N, 5.77; S, 6.62.

(1R,2R)-1-(4-Bromophenylsulfonamido)-1,2-dihydronaphthalen-2-yl-4-chlorobenzoate (4a)

4a was obtained as a white solid (29.0 mg, 56 %), mp 187 188 C; []20D = 72.7 (c = 1.00, CHCl3); IR (KBr, cm1)

3305(w), 3092(w), 3053(w), 2919(s), 2857(m), 1715(s), 1664(w), 1591(m), 1575(m), 1454(w), 1429(m), 1390(m), 1329(s), 1267(s), 1158(s), 1119(m), 1088(s), 1065(m), 1012(m), 979(w), 917(w), 844(m), 819(m), 802(m), 774(m), 755(s), 736(s), 699(w), 609(m), 556(m); 1H NMR (400 MHz, CDCl3) 7.69 (d, J = 8.0 Hz, 2H), 7.61 (d, J = 8.0 Hz, 2H),

7.43 (d, J = 6.4 Hz, 1H), 7.36 (d, J = 8.0 Hz, 2H), 7.26

7.32 (m, 4H), 7.13 (d, J = 6.4 Hz, 1H), 6.58 (d, J = 8.8 Hz,

1H), 5.89 (d, J = 9.6 Hz, 1H), 5.83 (d, J = 10.0 Hz,

1H), 5.24 (d, J = 7.2 Hz, 1H), 4.93 (t, J = 9.2 Hz,

1H); 13C NMR (100 MHz, CDCl3) 165.4, 140.2, 140.0, 133.0, 132.2, 132.1, 131.0, 130.2, 128.8, 128.7, 128.2, 127.5, 127.4, 127.1, 126.9, 125.5, 72.6, 57.2; MS (ESI) calcd for C23H17BrClNO4S (M+) 516.98, found 539.98 (M+Na)+.

Anal. calcd for C23H17BrClNO4S: C, 53.25; H, 3.30; N, 2.70; S, 6.18. Found: C, 53.17; H, 3.29; N, 2.70; S, 6.14.

(1R,2R)-1-((tert-Butoxycarbonyl)amino)-1,2-dihydronaphthalen-2-yl-4-chlorobenzoate (5a)

5a was obtained as a white oil (3.6 mg, 9 %), []20D = 26.3

(c = 1.00, CHCl3); IR (KBr, cm1) 3346(w), 3055(w),

2973(s), 2928(s), 1717(s), 1594(m), 1486(m), 1451(m), 1390(m), 1363(m), 1327(m), 1163(s), 1089(m), 1015(m), 853(m), 782(m), 757(m), 694(w), 624(w), 521(w); 1H NMR (400 MHz, CDCl3) 7.97 (d, J = 8.4 Hz, 2H), 7.41

(d, J = 7.2 Hz, 1H), 7.37 (d, J = 8.4 Hz, 2H), 7.29 (d, J=

4.0 Hz, 2H), 7.14 (t, J = 4.8 Hz, 1H), 6.59 (d, J = 9.6 Hz,

1H), 6.07 (dd, J = 2.8, 9.6 Hz, 1H), 5.75 (d, J = 7.6 Hz,

1H), 5.31 (d, J = 9.6 Hz, 1H), 4.72 (d, J = 9.6 Hz, 1H),

1.37 (s, 9H); 13C NMR (100 MHz, CDCl3) 165.5, 155.5, 139.6, 133.7, 132.2, 131.3, 130.1, 128.7, 128.5, 128.4, 128.3, 127.1, 126.4, 125.7, 80.0, 73.5, 52.9, 28.3; MS (ESI) calcd for C22H22ClNO4 (M+) 399.12, found 422.14 (M+Na)+. Anal.

calcd for C22H22ClNO4: C, 66.08; H, 5.55; N, 3.50. Found: C, 66.25; H, 5.54; N, 3.51.

Acknowledgments We are grateful to the National Natural Science Foundation of China (No. 20802021) and Guangzhou Pearl River New Star Plan of Science and Technology Project (No.2012J220005) for nancial support.

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