The first use of phosphahelicene in enantioselective organocatalysis is reported. New chiral phosphahelicenes have been prepared and enable highly enantioselective [3+2] cyclization reactions between arylidene‐ or alkylidenemalononitriles and γ‐substituted allenoates or cyanoallenes. These reactions afford cyclopentene derivatives in both high yields and diastereoselectivities, with enantiomeric excesses
Catalytic Asymmetric CN Bond Formation: Phosphine-Catalyzed Intra- and Intermolecular γ-Addition of Nitrogen Nucleophiles to Allenoates and Alkynoates
作者:Rylan J. Lundgren、Ashraf Wilsily、Nicolas Marion、Cong Ma、Ying Kit Chung、Gregory C. Fu
DOI:10.1002/anie.201208957
日期:2013.2.25
Pin the amine on the gamma: A new method has been developed for the γ‐addition of nitrogennucleophiles to γ‐substituted alkynoates or allenoates through intra‐ and intermolecular processes that are catalyzed by spirophosphine 1 (see scheme). An asymmetric version of this reaction affords enantioenriched pyrrolidines, indolines, and γ‐amino‐α,β‐unsaturated carbonyl compounds.
The phosphine-promoted [3 + 2] cyclizations between gamma-substituted allenoates and arylideneoxindoles have been applied to the stereoselective synthesis of spiro(cyclopentene)oxindoles with trisubstituted cyclopentene units. It has been demonstrated that PPh3 operates a very efficient control of the relative stereochemistry of the three stereogenic centers of the final spiranic products. Focused experiments have been carried out then so as to access carbocyclic analogues of an important series of anticancer agents inhibiting MDM2-p53 interactions.
Phosphine-Catalyzed Formation of Carbon−Sulfur Bonds: Catalytic Asymmetric Synthesis of γ-Thioesters
作者:Jianwei Sun、Gregory C. Fu
DOI:10.1021/ja101251d
日期:2010.4.7
only add to the gamma position of allenoates, overcoming their propensity to add to the beta position in the absence of a catalyst, but do so with very good enantioselectivity. Sulfur nucleophiles are now added to the three families of nucleophiles (carbon, nitrogen, and oxygen) that had earlier been shown to participate in catalyzed gamma additions. The phosphine catalyst of choice, TangPhos, had