Synthesis of Organic Compounds in the Removal of Ruthenium and the Development of a Novel Ruthenium Catalyzed Synthesis of Z-1,3-disubstituted dienes by Uphill Photocatalysis

Abstract

The removal of metal catalysts from crude reaction mixtures has become significant due to the development of metal catalyzed reactions in organic chemistry. Conventional methods for removal with silica gel have severe limitations, such as increased cost and silica gel hydrolysis. Towards this end we synthesized silica-supported aromatic isocyanide scavenger to remove ruthenium from ring closing metathesis reactions. These scavengers are strongly binding ligands and can quench the powerful metathesis reaction undertaken by ruthenium Grubbs complexes. They also proved to be significantly better than commercially available silica gel-based metal scavengers.

In addition to developing new scavengers for the quenching of metathesis reactions, we also sought to develop a new reaction methodology for our 1,3-dienes that could be synthesized through ene-yne metathesis. Initial studies undertook the development of a radical functionalization reaction through utilization of copper. However, results from the copper reaction led to us pursuing reactivity with photocatalysts. With a ruthenium photosensitizer we were able to access the Z-isomer of 1-aryl-1,3-dienes. We were also able to perform a sequential one-pot, tandem cross ene-yne metathesis/photoisomerization reaction, which provided access to a stereoconvergent synthesis of select 1,3-dienes. This is significant, since current cross ene-yne metathesis methods cannot stereoselectively deliver Z-1,3-dienes.