Preparation of 4-Diazoisoquinolin-3-ones via Dimroth Rearrangement and Their Extension to 4-Aryltetrahydroisoquinolin-3-ones

4-Diazoisoquinolin-3-ones were prepared efficiently via TBAB-promoted rearrangement of 4-diazoisochroman-3-imines under mild reaction conditions. The resulted 4-diazoisoquinolin-3-ones could be conveniently applied for the synthesis of 4-aryltetrahydroisoquinolin-3-ones either by the TfOH-catalyzed reaction with electron-rich arenes or by the BF3-promoted reaction with aryl aldehydes.