A novel rearrangement reaction. A single‐step conversion of tetrahydro‐1‐isoquinolinecarboxylic acids into 1‐isoquinolones

Abstract
The preparation of 2‐acyl‐6,7‐dimethoxy‐1,2,3,4‐tetrahydro‐1‐isoquinolinecarboxamides is described. The mixed anhydride of 2‐acyl‐6,7‐dimethoxy‐1,2,3,4‐tetrahydro‐1‐isoquinolinecarboxylic acid with isobutyl chloroformate was reacted with the corresponding hydrazines at — 10, — 15°. Besides those compounds, isoquinolones occur through a new side reaction. The structure of those products was established by13C and1H nmr and mass spectroscopy. A possible mechanism of the reaction is discussed.