Alkylation of the hippurate esters of trans 2-(p-substituted phenyl)cyclohexanol with benzyl bromide affords phenylalanine derivatives in high chemical yield. The reaction stereoselectivity varies from 20 to >98% depending on the aromatic group in the cyclohexyl auxiliary. A model that correctly predicts the sense of the induction is proposed.
Selective Formation of Functionalized α-Quaternary Malononitriles toward 5,5-Disubstituted Pyrrolopyrimidinones
作者:Alan Whitehead、Yong Zhang、Jamie McCabe Dunn、Edward C. Sherer、Yu-hong Lam、John Stelmach、Aaron Sun、Melisa Shiroda、Robert K. Orr、Sherman T. Waddell、Subharekha Raghavan
DOI:10.1021/acs.orglett.7b01930
日期:2017.9.1
A modular, selective approach to complex α-tertiary substituted malononitriles is reported. The method takes advantage of β-ester-substituted α,α-dinitrile alkenes as highly reactive, chemoselective electrophiles for 1,4-additions with organometallic nucleophiles to produce functionally and sterically dense all-carbon quaternary centers. In the presence of a chiral ester auxiliary bearing an aromatic