Rh(III)-Catalyzed Reaction of 4-Diazoisochroman-3-imines with (2-Formylaryl)boronic Acids To Access a Straightforward Construction of 5 H -Isochromeno[3,4- c ]isoquinolines.

An Rh(III)-catalyzed one-pot synthesis of 5 H -isochromeno[3,4- c ]isoquinolines from readily available 4-diazoisochroman-3-imines and (2-formylphenyl)boronic acids is reported. The cascade annulation involves a Rh(III)-catalyzed cross-coupling and an intramolecular nucleophilic addition-elimination process. A series of biologically important 5 H -isochromeno[3,4- c ]isoquinolines were obtained in good to excellent yields. The method can be extended to synthesize 7 H -isochromeno[3,4- b ]thieno[3,2- d ]pyridines and 7 H -isochromeno[3,4- b ]thieno[2,3- d ]pyridines from the corresponding heteroaryl boronic acids.