Heterobimetallic Pd-Sn Catalysis: A Suzuki, Tandem Ring-Closing Sequence toward Indeno[2,1-b]thiophenes and Indeno[2,1-b]indoles

Indeno[2,1-b]thiophene and indeno[1,2-b]indole motifs have been obtained in moderate to good yields from easily available substituted boronic acids, 2-bromo aryl/vinyl aldehydes, and nucleophiles such as arenes/heteroarenes and others using a catalytic combination of bimetallic Pd-Sn and AgPF6. This formal three-component coupling involves a Suzuki reaction followed by nucleophile assisted tandem ring closure. The sequential synthesis of substituted heterocycle-fused indenes, benzofluorene, and fluorenes was also accomplished.