Conformational behaviour of medium-sized rings. Part 5. Transannular reactions of (16Z)-8,9-dihydro-8-methyl-7H-dinaphth-[1,8-cd:1′,8′-hi]azacycloundecine and (12Z)-6,7-dihydro-6-methyl-5H-dibenz[c,g]azonine. Two examples of ‘reverse Hofmann eliminations’

Abstract

The olefinic double bonds in the cyclic ene-amines (5) and (8) have been shown to have the cis-configuration since two conformational diastereoisomers are formed in each case on quaternisation at nitrogen. The eleven-membered ring ene-amine (5), which is conformationally stable on the ¹H n.m.r. time-scale up to +160 °C, undergoes transannular reactions involving the carbon–carbon double bond and the nitrogen atom in acidic, neutral, and basic media. Although the nine-membered ring ene-amine (8), which is conformationally mobile on the ¹H n.m.r. time-scale at room temperature, also undergoes transannular reactions involving the carbon–carbon double bond and the nitrogen atom in acidic and neutral media, more vigorous reaction conditions are required.