Photochemistry of pyridyl azides and diazo ketones in matrix and in solution

Abstract

This paper describes recent advances in the photochemistry of 2-pyridyl azides/tetrazolo[1,5-a]pyridines, which is a viable synthetic source of novel 1,3-diazepines via ring expansion of the 2-pyridylnitrenes to 1,3-diazacycloheptatetraenes. The nitrenes have been observed by Ar matrix ESR spectroscopy, and the diazacycloheptatetraenes by Ar matrix IR spectroscopy. Trapping with nucleophiles in solution at room temperature leads to 1H-1,3-diazepines, some of which are stable, distillable compounds, whereas others isomerize to stable 5H-1,3-diazepines. New chemistry in the field of Wolff rearrangement of pyridine-based diazoketones leads to 2- and 3-azafulvenones, which dimerize or tetrameriz..