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Abstract
The intramolecular exocyclic nitrone-olefin cycloaddition reaction has been studied and utilized in the construction of a variety of bridged bicycloalkanes. This unique methodology presents a new route into the syntheses of those natural products containing the bridged bicycloalkane subunit. Application of this method has resulted in the first total synthesis of the antifertility agent, ((+OR-))-7,12-secoishwaran-12-ol.
In addition, the intermolecular exocyclic nitrone-olefin cycloaddition has been studied and applied in the syntheses of a variety of 1-azaspirocycles. Further application of this methodology for the construction of the alkaloid perhydrohistrionicotoxin was studied, using the N-benzylnitrone of 2-butyl-3-hydroxycyclohexanone with a variety of dipolarophiles. Failure of the cycloaddition prompted the addition of allylmagnesium bromide to the N-benzylimine of 2-butyl-3-hydroxycyclohexanone to provide an intermediate allyl-substituted amine. Further manipulation to the 1-azaspirolactam led to the product containing the incorrect stereochemistry.
A new method for the construction of vinylic sulfones is also presented. (alpha)-Trimethysilylation of an allylic sulfonyl anion followed by treatment with acid caused protodesilylation, yielding the corresponding vinylic sulfone. A variety of systems were synthesized to demonstrate the generality of this method.
