title: Bridgehead nitrogen heterocycles which contain the quinazoline moiety -- synthesis and cycloaddition of 1,2-dihydroquinazoline 3-oxides.
abstract: A novel synthesis of 1,2-disubstituted 1,2-dihydroquinazoline 3-oxides 8 and the first ever examples of 1,3-dipolar trapping of these nitrones to homonuclear dipolarophiles is described. The new dipoles 8 reacted with N-methyl maleimide, generating diastereomeric adducts 14-16. In the reaction between 8 and dimethyl acetylenedicarboxylate, primary cycloadducts 17 and/or stable rearrangement products, azomethine ylides 18, are formed depending on the substitution pattern of the dipole. The structure of 18c is unambiguously assigned by X-ray crystallographic analysis. An X-ray crystal structure determination is also presented for the cyclopropylisoxazoloquinazoline 22 formed by a [3 + 2] addition of 8a to 21, the dimethyl acetylenedicarboxylate tetramer.
authors.affiliation: Department of Chemistry, National University of Ireland, Maynooth, Ireland.
authors.forename: Frances
authors.initials: F
authors.lastname: Heaney
authors.forename: Tomas
authors.initials: T
authors.lastname: McCarthy
authors.forename: Mary
authors.initials: M
authors.lastname: Mahon
authors.forename: V
authors.initials: V
authors.lastname: McKee