Cobalt-Catalysed [6+2] Cycloaddition of Internal Alkynes and Terminal ­Alkenes with Cycloheptatriene

Abstract

The cobalt-catalysed [6+2] cycloaddition of cycloheptatriene with internal alkynes as well as with terminal alkenes is described. The cycloaddition process is most efficiently catalysed by cobalt dibromide[bis(triisopropylphosphite)] complexes in dichloromethane as the solvent of choice. In the cobalt-catalysed reaction of cycloheptatriene with norbornene an unexpected tricyclic [2+2] cycloaddition product was isolated in excellent yields.

Key words

alkyne - alkene - cobalt - cycloaddition - dienes

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8

dppp: 1,3-bis(diphenylphosphino)propane;
dppb: 1,4-bis(diphenylphosphino)butane;
dpph: 1,6-bis(diphenylphosphino)hexane;
dppf: 1,1′-bis(diphenylphosphino)ferrocene.