Sterically constrained 'roofed' 2-thiazolidinones as excellent chiral auxiliaries

The "roofed" chiral 2-thiazolidinones, which are sterically congested and conformational rigid, and which are prepared by the 4+2] cycloaddition of 2-thiazolone to the cyclic dienes, dimethylanthracene and hexamethylcyclopentadiene, followed by optical resolution with (1S,2R)-2-methoxy-1-apocamphanecarbonic acid (MAC acid) are of considerable promise for use as chiral auxiliaries for the alkylation of enolates.