Highly Z-selective Julia–Kocienski Olefination Using N-sulfonylimines and Its Mechanistic Insights from DFT Calculations

The Julia–Kocienski (JK) olefination is a reliable method for E-selective olefination; however, highly Z-selective variants are scarce. Here, we report a highly Z-selective JK olefination (with a Z ratio up to >99:1) using N-sulfonylimines as the electrophilic partners instead of aldehydes. This method showed broad substrate tolerance, accommodating various functional groups, including electron-donating/withdrawing groups, amides, halogens, carboxylic acids, and hydroxyls. DFT calculations revealed that Z-selectivity is determined mainly during the 1,2-addition step. This study enhances the toolkit for Z-selective olefination in organic synthesis.