Rhodium-catalysed synthesis of fused pyrimidine derivatives employing N-sulfonyl-1,2,3-triazoles as a 1-aza-[4C] synthon.

• N -sulfonyl-1,2,3-triazole was used as a 1-aza-[4C] synthon. • Excellent chemoselectivity was observed. • Fused pyrimidine and seven-membered 1 H -1,4-diazepine were synthesized effectively. A new synthetic application of N -sulfonyl-1,2,3-triazoles acting as a 1-aza-[4C] synthon via the 1,2-shift reaction of an α-imine rhodium carbene was developed for the synthesis of fused pyrimidine derivatives. The high reactivity of the strained three-membered 2 H -azirine ring facilitated the unusual cyclization of electron-deficient dienes with electron-deficient dienophiles. The compatibility was good with common functionalities tolerated. Excellent chemoselectivity was observed, and no reactions occurred between the rhodium carbene and 2 H -azirine. The products could be converted into seven-membered multi-functionalized 1 H -1,4-diazepine derivatives, illustrating the potential application of the protocol in medium-sized N -heterocycle synthesis. [ABSTRACT FROM AUTHOR]