Nickel-Catalyzed Allylic Alkylation with Diarylmethane Pronucleophiles: Development and Mechanistic Insight

• Published in: Angewandte Chemie International Edition 2015-12, Vol.55 (3), p.1070-1074
• Main Authors: Sha, Sheng-Chun, Jiang, Hui, Mao, Jianyou, Bellomo, Ana, Jeong, Soo A, Walsh, Patrick J.
• Format: Article
• Language: English
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201507494

Palladium-catalyzed allylic substitution reactions are among the most efficient methods to construct C–C bonds between sp 3 -hybridized carbons. In contrast, much less work has been done with nickel catalysts. This may be due, in part, to the different mechanisms of allylic substitution reactions. Palladium catalysts generally undergo substitution via a “soft” nucleophile pathway, wherein the nucleophile attacks the allyl group externally. Nickel catalysts are usually paired with “hard” nucleophiles, which attack the metal before C–C bond-formation. Herein is introduced a rare nickel-based catalyst that promotes substitution with diarylmethane pronucleophiles via the “soft” nucleophile pathway. Preliminary studies on the asymmetric allylic alkylation are promising. Just a softy : Contrary to what would be predicted, organosodium nucleophiles derived from diarylmethane pronucleophiles are shown to behave as soft nucleophiles in Ni-catalyzed allylic substitution reactions. This general reaction (21 examples) is demonstrated to proceed by the double inversion pathway. A promising asymmetric version (92% ee) is demonstrated.