using traditional alkylation methods under basic conditions. The approach enables a highly stereoselective synthesis of quaternary (thio)oxindoles via a formal allylation-asymmetric Michaeladdition sequence. These adducts are versatile synthons for spirocyclic (thio)oxindoles. Initial biological studies reveal that chiral thiooxindoles show promising antiproliferation activity that is better than that
A highly regio- and enantioselective organocatalyzed Michael addition of malonates to nitrodienes
作者:Raghunath Chowdhury、Ganga B. Vamisetti、Sunil K. Ghosh
DOI:10.1016/j.tetasy.2014.02.007
日期:2014.4
An organocatalyzed direct Michael addition of unsubstituted/substituted malonates, acetoacetate, or acetylacetones to conjugatednitrodienes using a cinchona alkaloid-based thiourea catalyst is disclosed. The addition products were formed in high yields and regioselectivity. The enantioselectivities of the addition products were high in most cases and could significantly be improved upon by a single
“On Water” Organocatalyzed [4 + 2] Cycloaddition of Enones and Nitro Dienes for the Enantioselective Synthesis of Densely Substituted Cyclohexanones
作者:Ganga B. Vamisetti、Raghunath Chowdhury、Mukesh Kumar、Sunil K. Ghosh
DOI:10.1021/acs.orglett.6b00460
日期:2016.5.6
with a nitro group in the 4-position from enones and nitro dienes under ambient conditions in good yield, with good diastereoselectivity, and with excellent enantioselectivity. An appreciable rate enhancement by water was observed compared to organic solvents. Mechanistic analysis of the reaction suggests that it followed an endo [4 + 2] cycloaddition with enamine of enone as diene and nitro diene as