The non-benzenoid aromatics, tropones and tropolones, are found in various natural products such as colchicine and hinokitol, which possess significant biological activities. The traditional methods to construct the tropone skeletons include oxidation of cycloheptatriene and [4+3] cycloadditions. In addition, the total synthesis of colchicine and its analogues requires laborious organic transformations in the formations of 6-7-7 fused rings systems.Transition metal-catalyzed carbocyclization and cycloaddition reactions have proven to be among the most efficient methods for constructing complex polycyclic systems. We have reported a series of Rh-catalyzed carbocyclizations (i.e. SiCaC, SiCaT, CO-SiCaT) 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.

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

244th National Meeting (2012)

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