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

The Julia–Kocienski (JK) olefination is a powerful and widely used method for alkene synthesis, particularly favoring E-selective olefination. However, highly Z-selective variants remain underexplored. In this study, we report a highly Z-selective JK olefination (Z ratio >99:1) using N-sulfonylimines as electrophilic partners instead of traditional aldehydes. This approach exhibits broad substrate compatibility, accommodating a variety of sulfones and N-sulfonylimines with functional groups such as electron-donating and electron-withdrawing substituents, amides, halogens, carboxylic acids, and hydroxyls. The reaction enables efficient synthesis of valuable Z-alkenes, including (Z)-α,β-unsaturated amides, Z-alkenyl halides, and Z-trisubstituted alkenes, under mild and general conditions. Mechanistic investigations using DFT calculations revealed that Z-selectivity is established during the 1,2-addition step, contrasting with conventional Z-selective JK olefination, where the Smiles rearrangement step governs selectivity. This study not only expands the synthetic arsenal for stereoselective olefin synthesis but also provides a versatile and general method for constructing Z-olefins with high precision and efficiency.