Synthesis of Novel Allocolchicine Analogues with a Pyridine C-Ring through Intermolecular Vollhardt Diyne-Nitrile Cyclotrimerization

[摘要]：A short synthesis of new allocolchicinoids with a pyridine C-ring and an oxa-B-ring was developed exploiting a cobaltcatalyzed intermolecular [2+2+2] cycloaddition (diyne-nitrile cyclotrimerization). Starting from readily accessible 3,4,5-trimethoxybenzaldehyde or 3,4,5-trimethoxyacetophenone, the (racemic) target compounds were regioselectively obtained in 15-20% overall yield (five steps).

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