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A highly chemo- and diastereoselective protocol for the cyclopropanation of tertiary allylic amines with Shi's carbenoid [CF 3 CO 2 ZnCH 2 I] 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(CH 2 I) 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. © 2010 Elsevier Ltd. All rights reserved.

Original publication

DOI

10.1016/j.tet.2010.08.055

Type

Journal article

Journal

Tetrahedron

Publication Date

23/10/2010

Volume

66

Pages

8420 - 8440