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Enantioselective Phosphine‐Catalyzed Formal [4+4] Annulation of α,β‐Unsaturated Imines and Allene Ketones: Construction of Eight‐Membered Rings

2017; Wiley; Volume: 56; Issue: 45 Linguagem: Inglês

10.1002/anie.201707183

1521-3773

Huanzhen Ni, Xiaodong Tang, Wenrui Zheng, Weijun Yao, Nisar Ullah, Yixin Lü,

Asymmetric Hydrogenation and Catalysis

Abstract The first highly enantioselective phosphine‐catalyzed formal [4+4] annulation has been developed. In the presence of amino‐acid‐derived phosphines, the unprecedented [4+4] annulations between benzofuran/indole‐derived α,β‐unsaturated imines and allene ketones proceeded smoothly, thus affording azocines, bearing either a benzofuran or an indole moiety, in excellent yields and with nearly perfect enantioselectivities (≥98 % ee in most cases). This work marks the first efficient asymmetric construction of optically enriched eight‐membered rings by phosphine catalysis.