Magnesium iodide promoted reactions of nitrones with cyclopropanes: a synthesis of tetrahydro-1,2-oxazines.
Anhydrous magnesium iodide (MgI(2)) is shown to be an effective promoter of the "homo 3+2" dipolar cycloaddition of nitrones with 1,1-cyclopropane diesters. In almost all cases the products tetrahydro-1,2-oxazines are formed in excellent yields. The reactions are highly diastereoselective for a cis relationship between the substitutents at the 3- and 6-positions on the tetrahydrooxazine ring. As an alternative to using a preformed nitrone, the reaction may be performed in a 3-component sense by combining an aldehyde, an hydroxylamine, and the cyclopropane in the presence of catalytic MgI(2).
Ganton
Michael D
MD
Department of Chemistry, The University of Western Ontario, London, Ontario, Canada, N6A 5B7.
Kerr
Michael A
MA