Investigations in dienamine chemistry.

Abstract

Reaction of the pyrrolidine dienamines of ~1,8a-2-octalones with methyl vinyl ketone is complex. In methanol as solvent, the reaction occurs primarily with the linear dienamine isomer and results in annulation of the 8,8a-positions and, to a lesser extent, the 1,2-positions to give the corresponding octahydro-1 Hbenzo[d]naphthalene-2,10(3H,111-1)-dione and 3,4,5,6,7,8,8a,9-ctahydrophenanthren-2(10H)-one respectively. In toluene the dienamines react mainly in their cross-conjugated form. Diels-Alder addition of methyl vinyl ketone occurs across the 3,8a-positions to give the corresponding 9-acetylperhydro-2,4aethanonaphthalen-3-one and annulation of the 2,3-positions gives the 4,4a,5,5a,6,7,8,9-octahydroanthracen-2(3H)-one. The reaction of methyl vinyl ketone with the pyrrolidine dienamine of 4amethyl- 5-oxo-~ 1,8a-2-octalone is reported to give the aromatic product 3a, 7dimethyl- 2,3,3a,4,5,6-hexahydrophenalen-3,6-dionearisingfromp,o-annulation and in a related investigation with dienamines derived from isophorone it was reported that only products of Stork alkylation and Diels-Alder cycloaddition were isolated, there being no evidence for the reaction of methyl vinyl ketone with either the endo- or exocyclic o-positions of the dienamines. In an attempt to ascertain the reason for the apparently random changes in the regioselectivity of these related reactions some of this work was repeated and the reaction of methyl vinyl ketone applied to two other dienamines derived from 5,6,7,7a-tetrahydroindan-5-one and 4a,6-dimethyl-5-oxo-~1,8a-2-octalone.

The reactions proved to be more complex than reported and several additional products have been isolated. Finally, reaction of phenyl vinyl ketone with dienamines derived from a1,8a_2-octalone was investigated. With the exception of the reaction of the 4amethyl dienamine, the main products isolated were those arising from addition of p.henyl vinyl ketone across the 3,8a-position to give the corresponding 9-benzoylperhydro-,4a-ethanonaphthalen-3-one. Reaction of the 4a-methyl dienamine with two equivalents of phenyl vinyl ketone gave a product tentatively assigned as the octahydrophenalenone. The mechanism of formation and spectral properties of the various products are discussed.