Conformational analysis, spectral and catalytic properties of 1,3-thiazolidines, ligands for acetophenone hydrosilylation with diphenylsilane

2-Aryl- and 2-furyl-4-carboxy-1,3-thiazolidines were synthesized. Their spectral properties were studied, and conformational analysis was performed. It was shown that they exist in solution as an equilibrium of neutral and zwitter-ion forms. The influence of the nature of substitutents and of their location in a benzene ring of thiazolidines as ligands of rhodium complexes on acetophenone hydrosilylation with diphenylsilane was examined. Thiazolidines containing donor substituents in the para-position of the benzene ring were found to be the most effective; maximal asymmetrical induction (55% ee) was reached in the presence of 2-(4-methoxyphenyl)-4-carboxy-1,3-thiazolidine.