期刊
TETRAHEDRON
卷 66, 期 43, 页码 8420-8440出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2010.08.055
关键词
Cyclopropanation; Allylic amines; Allylic carbamates; Simmons-Smith; Shi's carbenoid
A highly chemo- and diastereoselective protocol for the cyclopropanation of tertiary allylic amines with Shi's carbenoid [CF3CO2ZnCH2I] is described. The high levels of diastereoselectivity observed in these reactions may be attributed to chelation of the nitrogen atom to the zinc reagent, which then transfers a methylene unit to the syn-face of the olefin. Furthermore, a stereodivergent protocol for the cyclopropanation of a range of allylic carbamates has been developed, which provides access to both diastereoisomers of the corresponding cyclopropanes with very high levels of diastereoselectivity: cyclopropanation with the Wittig-Furukawa reagent [Zn(CH2I)(2)] proceeds under chelation control to give the corresponding syn-product, whilst reaction with Shi's carbenoid proceeds under steric control to give the corresponding anti-cyclopropane, in >95:5 dr in both cases. (C) 2010 Elsevier Ltd. All rights reserved.
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