Two Cycles with One Catch: Hydrazine in Ugi 4-CR and Its Postcyclizations

Isocyanide-based multicomponent reactions (IMCR) are by far the most versatile reactions that can construct relatively complex molecules by one-pot synthesis. More importantly, the development of post IMCR modifications significantly improves the scaffold's diversity. Here, we describe the use of N-Boc protected hydrazine together with a-amino acid derived isocyanides in the Ugi tetrazole reaction and its post cyclization under both acidic and basic conditions. The cyclization in acidic conditions was conducted in a one pot fashion, which give 7-aminotetrazolopyrazinone (6) and tetrazolotriazepinone (7) cyclic products. The post cyclization under basic condition could selectively afford Boc-protected 7-aminotetrazolopyrazinone (8) products in yield of 38-87%.