TRANS-ANNULAR REACTIONS OF DIBENZO[A,D]CYCLOALKENES .2. SYNTHESIS OF BRIDGEHEAD SUBSTITUTED DIBENZO[A,D]CYCLOALKENIMINES BY A REGIOSPECIFIC TRANS-ANNULAR AMINE TO OLEFIN ADDITION

New synthetic approaches to dibenzo[a, d]cyclohepten-5, 10-imines (2) and to dibenzo[a, d]cycloocten-5, 12-and -6, 12-imines (3 and 1, respectively) have been devised. These routes have been designed specifically to allow for incorporation of alkyl substituents at the bridgeheads. They make use of an unusual, regiospecific, intramolecular amine to olefin addition to establish both the nitrogen bridge and the bridgehead alkyl group in a single step. Thus, 5 is converted rapidly (<30 min) and regiospecifically to 6 upon treatment with a small amount of n-butyllithium in tetrahydrofuran at room temperature. Entropic bias provided by the carbon skeleton and a radical mechanism mediated by the benzhydryl olefin are postulated to facilitate and direct this transformation. © 1979, American Chemical Society. All rights reserved.