Nitration of Heteroaryltrimethyltins by Tetranitromethane and Dinitrogen Tetroxide: Mechanistic Aspects, Scope and Limitations
The nitration of 2-(trimethylstannyl)heteroarenes by tetranitromethane (TNM) or dinitrogen tetroxide has been shown to be possible when the HOMO energy of the heteroaryltin is high enough to allow the formation of the corresponding radical cation. The reaction proceeds through a charge-transfer complex between heteroaryltin and TNM, followed by a single-electron transfer, which is enhanced under sunlamp irradiation. Accordingly, 2-nitrobenzo[b]furan, 2-nitrobenzo[b]thiophene, 2-nitropyridine and 2-nitroindoles were obtained by this method. However, the nitration of 2-stannylated pyrimidine or of stannylated 1,3,5-triazines has been shown to be impossible, due to the low energy of their HOMO orbitals. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)