Two-carbon ring expansion of isatin: a convenient construction of a dibenzo[b,d]azepinone scaffold

A unique two-carbon ring expansion of isatin has been achieved to conveniently construct the functionalized dibenzo[b,d]azepin-6-one scaffold in moderate to high yields, and the two carbon sources are different: one carbon is from the N-substituent of pyridinium bromide and the other is from indene-1,3-dione.