Diels–Alder reactions of acyclic α-cyano α,β-alkenones: a new approach to highly substituted cyclohexene system
摘要:
The Diels-Alder reactions of a variety of acyclic a-cyano a,p-unsaturated ketones 8 have been investigated. With the assistance of boron trichloride, these compounds were found to undergo the cycloaddition readily with dienes to give the corresponding adducts 9 in good to high yields. In addition, some of 9 could be further subjected to the reductive alkylation reactions using lithium naphthalenide (LN) and an appropriate alkylating agent, thus allowing for the generation of highly substituted cyclohexenes 10 with the replacement of the cyano group with an alkyl substituent. (C) 2009 Elsevier Ltd. All rights reserved.
A remote β,γ-regioselective asymmetric inverse-electron-demand oxa-Diels–Alder reaction between allylic ketones and α-cyano-α,β-unsaturated ketones has been developed through induced extended dienamine catalysis of a cinchona-derived primary amine. A spectrum of densely substituted dihydropyran frameworks were efficiently produced with excellent enantioselectivity and fair to exclusive diastereoselectivity
Enantioselective synthesis of substituted pyrans via amine-catalyzed Michael addition and subsequent enolization/cyclisation
作者:Utpal Das、Chan-Hui Huang、Wenwei Lin
DOI:10.1039/c2cc31445b
日期:——
An organocatalytic construction of optically enriched substituted pyran derivatives via amine-catalyzed Michael addition and subsequent enolization/cyclisation has been described starting from electronically poor alkenes. Functionalized pyrans were obtained in high enantioselectivities (up to 96%) and good yields (up to 90%) having three contiguous chiral centers.
Phosphine-catalyzed [3 + 2] annulation of β-sulfonamido-substituted enones with <i>trans</i>-α-cyano-α,β-unsaturated ketones for the synthesis of highly substituted pyrrolidines
To synthesize highly substituted pyrrolidines, we developed a phosphine-catalyzed [3 + 2] annulation of β-sulfonamido-substituted enones with trans-α-cyano-α,β-unsaturated ketones. We prepared a series of pyrrolidines under mild conditions with high yields and moderate-to-good diastereoselectivities. A catalytic mechanism for this reaction is suggested.
While phosphine-mediated reactions have been extensively explored over the past few decades, the catalytic cyclopropanation reaction via a phosphonium ylide pathway has been significantly underdeveloped, and an intermolecular version still remains to be disclosed. Presented herein is a catalytic cyclopropanation reaction between readily available benzylbromides and activated alkenes, such as α-cyano