Synthesis of Highly Substituted Indole Alkaloid Species via [4+1] Cyclization of Nucleophilic Carbenes and Indole Isocyanates

Thermally induced [4 + 1 ] cyclization between indole isocyanates and dimethoxycarbene or bis(propylthio)carbene has been achieved with good chemical efficiency. The methodology provides rapid access to fused pyrroloindole substructures commonly found in a variety of indole alkaloid natural products.