Gao N, Guo X.-W, Zheng S.-C, Yang W.-K, Zhao X.-M * Tongji University, Shanghai and
Dalian University of Technology, P. R of China
Iridium-Catalyzed Enantioselective Allylation of Sodium 2-Aminobenzenethiolate: An
Access to Chiral Benzo-Fused N,S-Heterocycles.
Tetrahedron 2012;
68: 9413-9418
Key words
iridium - allylation - N,S-heterocycles
Significance
Iridium-catalyzed enantioselective allylation has emerged as a powerful method to
synthesize structurally diverse, chiral molecules. Despite much progress in the area
of enantioselective carbon–sulfur bond formation using iridium, there have been
no reports on the use of sodium 2-aminobenzenethiolate as a nucleophile in this class
of reaction. Despite, the potential of this substrate class to encounter detrimental
‘ortho-substituent effects’ on stereoselectivity, Zhao accomplishes selective and highly
enantioselective S-allylation.
Comment
The authors report an iridium-catalyzed asymmetric S-allylation reaction using chiral
phosphoramidite ligands. The method is highly regio- and enantioselective for a variety
of aryl- and alkyl-substituted allyl carbonates. Yields range from moderate to good
with excellent enantiocontrol. In most cases, the authors are able to completely inhibit
bisallylation and maintain high levels of branched-to-linear selectivity. The author
use the products to synthesize enantioenriched N,S-heterocycles via an N-allylation/ring-closing
metathesis sequence.
