Nickel‐Catalyzed Transfer Hydrogenation of α,β ‐Enones Using NH 3 ·BH 3 : Global Reduction of Chalcon
Junyu Pan, Shuo Zhang, Fangshu Duan, Wenjing Tan, Meiting Guo, Caiyun Liang, Wanfang LiABSTRACT
A nickel‐catalyzed transfer hydrogenation protocol has been developed for the global reduction of α,β ‐unsaturated ketones to 1,3‐diarylpropanes using ammonia borane (NH 3 ·BH 3 ) as the hydrogen source. This method enables the direct conversion of readily available chalcones into valuable 1,3‐diarylpropane motifs, which are prevalent in numerous bioactive natural products and pharmaceutical agents. The catalytic system, consisting of Ni(acac) 2 and 4,4′‐dimethoxy‐2,2′‐bipyridine ( L 8 ), operates under mild conditions (EtOH, 80°C) and exhibits broad substrate compatibility, accommodating a wide range of electronically and sterically diverse aryl substituents on both sides of the enone. A variety of substituted chalcones, including naphthyl and heteroaryl derivatives, are transformed into the corresponding products in moderate to excellent yields (up to 98%). The protocol also efficiently reduces extended dienone systems to linear alkylarenes, offering an alternative to classical Friedel–Crafts routes. Mechanistic studies suggest that the reaction may proceed via sequential C═O reduction and C═C hydrogenation, with allylic alcohol intermediates being readily converted. This work provides a practical, robust, and complementary approach to the synthesis of 1,3‐diarylpropanes, highlighting the utility of nickel catalysis and ammonia borane in sustainable organic synthesis.