Preparation of benzoheterocyclic carbaldeydes

The preparation of benzoheterocyclic carbaldehydes in the 2-amino-substituted benzothiazole, benzoxazole and benzimidazole series is described. Starting with the methyl-substituted 2-aminobenzoheterocycle, the nitrogen is protected as an N,N-diBoc derivative. Next, free radical halogenation of the methyl group with NBS/AIBN affords the N(Boc)2-protected benzylic dibromide which is directly used in the final step. A mild silver nitrite/dimethylsulfoxide-mediated conversion of the dibromide to the aldehyde functionality completes the process.