The stereochemistry of 1,3-dipolar cycloaddition of internally H-bonded chiral methylenenitrones
作者:Shaikh A. Ali、Muhammad Z.N. Iman
DOI:10.1016/j.tet.2007.06.067
日期:2007.9
A study of diastereoselectivity in the cycloaddition reactions of a series of mono- and disubstituted alkenes with two chiral, internally H-bonded methylenenitrones has been carried out. The high degree of stereochemical control in the presence of anhydrous magnesium bromide has been explained in terms of a metal chelated transition state. Intramolecular cycloaddition involving a methylenenitrone containing an alkene moiety linked to a nitrogen gave a stereoselective addition product. (c) 2007 Elsevier Ltd. All rights reserved.
Oxazoline N-Oxide-Mediated [2+3] Cycloadditions: New Access to Quaternary Asymmetric Centres
Cycloadditions between camphor-derived oxazoline N-oxide I and dipolarophiles 5 or 8 afforded adducts 6 and 9, respectively, with almost complete regio- and stereoselectivity depending on the substitution patterns of the dipolarophiles.