title: Regio- and stereochemical studies on the nitroso-Diels-Alder reaction with 1,2-disubstituted dienes.
abstract: The regioselectivity of the nitroso-Diels-Alder reaction between unsymmetrical acyclic dienes and Boc-nitroso (Boc=tert-butoxycarbonyl) reagent or the Wightman chiral chloronitroso reagents has been studied. With the Boc-nitroso reagent, the selectivity is a consequence of steric effects at the C1-position in the diene and electronic effects at the C2-position in the diene. The combination of an unprotected hydroxyethyl side chain at C1 and an electron-withdrawing group at C2 allows complete regioselectivity in favour of the proximal isomer. The same isomer was obtained exclusively with the chiral nitroso reagent with high enantioselectivities. A model based on steric effects is proposed.
authors.affiliation: Institut de Chimie Moléculaire et des Matériaux d'Orsay, Bâtiment 410, Université de Paris-Sud, 91405 Orsay (France), Fax: (33) 1-69-15-46-79.
authors.forename: Gilles
authors.initials: G
authors.lastname: Galvani
authors.forename: Robert
authors.initials: R
authors.lastname: Lett
authors.forename: Cyrille
authors.initials: C
authors.lastname: Kouklovsky
keywords: asymmetric synthesis; cycloadditions; enol phosphate; nitroso-Diels-Alder reaction; regioselective