Regio- and Stereoselective Domino Synthesis of Oxazolo Fused Pyridoindoles and Benzofurooxazolo Pyridines from ortho-Alkynylarylaldehydes.

An environmentally benign Au(III)-catalyzed regio- and stereoselective domino synthesis of oxazolo fused pyridoindoles 7a–v and benzofurooxazolo pyridines 8a–n by the reaction of o-alkynylaldehydes 4a–t and 5a–k with (S)-phenylglycinol 6a and (R)-phenylglycinol 6b under mild reaction conditions using water as reaction medium is reported. The reaction proceeded via selective C–N bond formation on the more electrophilic alkynyl carbon through 6-endo-dig cyclization. The reaction tolerates a wide variety of functional groups. The developed chemistry has been successfully extended for the synthesis of a diverse class of γ-carbolines and benzofuro[3,2-c]pyridines using corresponding ester hydrochlorides of serine, threonine, and cystine as a nitrogen source.