Ziegler DT, Riesgo L, Ikeda T, Fujiwara Y, Fu GC. Biphenyl-derived phosphepines as chiral nucleophilic catalysts: enantioselective [4+1] annulations to form functionalized cyclopentenes.
Angew Chem Int Ed Engl 2014;
53:13183-7. [PMID:
25287684 DOI:
10.1002/anie.201405854]
[Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 07/15/2014] [Indexed: 11/10/2022]
Abstract
Because of the frequent occurrence of cyclopentane subunits in bioactive compounds, the development of efficient catalytic asymmetric methods for their synthesis is an important objective. Introduced herein is a new family of chiral nucleophilic catalysts, biphenyl-derived phosphepines, and we apply them to an enantioselective variant of a useful [4+1] annulation. A range of one-carbon coupling partners can be employed, thereby generating cyclopentenes which bear a fully substituted stereocenter [either all-carbon or heteroatom-substituted (sulfur and phosphorus)]. Stereocenters at the other four positions of the cyclopentane ring can also be introduced with good stereoselectivity. An initial mechanistic study indicates that phosphine addition to the electrophilic four-carbon coupling partner is not the turnover-limiting step of the catalytic cycle.
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