Colchicine, a secondary metabolite of autumn crocus and one of the oldest known drugs, is originally extracted from the poisonous plant meadow saffron (Colchicum autumnale L.). The traditional methods to synthesize colchicine and its analogues include oxidation of cycloheptatriene and [4+3] cycloadditions. In addition, the difficulties inherent to the target molecule rest with the regioselective structure of the highly oxidized ring C within the distinctive 6, 7, 7-membered ring system.Transition metal-catalyzed carbocyclization and cycloaddition reactions have proven to be among the most efficient method for synthesizing complex polycyclic systems. We have reported a series of Rh-catalyzed new cascade carbocyclizations and higher order cycloaddition reactions, which give novel fused-cyclic products. We present here the application of Rh-catalyzed [2+2+2+1] cycloaddition to the one-step formation of the 6-7-7-5 fused-tetracyclic scaffold of colchicinoids, mainly including the preparation of ortho-Phenylenetriynes for this rapid access to novel colchicinoids. 

Preparation of <i>ortho</i>-phenylenetriynes for rapid access to novel colchicinoids through Rh-catalyzed [2+2+2+1] cycloaddition

248th National Meeting (2014)

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Preparation of ortho-phenylenetriynes for rapid access to novel colchicinoids through Rh-catalyzed [2+2+2+1] cycloaddition