Article

Enantioselective synthesis of chiral allenoates by guanidine-catalyzed isomerization of 3-alkynoates.

Department of Chemistry, 3 Science Drive 3, National University of Singapore, Singapore 117543.
Journal of the American Chemical Society (impact factor: 9.91). 06/2009; 131(21):7212-3. DOI:10.1021/ja901528b pp.7212-3
Source: PubMed

ABSTRACT We report that chiral bicyclic guanidine 1 is found to catalyze the isomerization of alkynes to chiral allenes with high enantioselectivities. This Brønsted base catalyzed 1,3-proton shift reaction, an efficient and atom economical reaction, proceeds through deprotonation and protonation sequences. The axial chirality of the allenes is efficiently transferred to functionalized butenolides and cycloaddition products. We also successfully demonstrate the stereospecific synthesis of butenolide through allenoate cyclization with a catalytic cationic Au(I) complex.

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Keywords

allenes
 
allenoate cyclization
 
axial chirality
 
Brønsted base catalyzed 1,3-proton shift reaction
 
chiral allenes
 
chiral bicyclic guanidine 1
 
deprotonation
 
efficient
 
functionalized butenolides
 
isomerization