A new, easy access to the 6-aminoperhydro-1,4-diazepine scaffold under ultrasound and microwave irradiation

A novel, efficient, and rapid synthesis of the 6-aminoperhydro-1,4- diazepine scaffold is reported. It was promoted by microwave or sequential ultrasound/microwave irradiation under solvent-free conditions or in solution. Protected ethylenediamine derivatives and N-Boc-serinol dimesylate underwent rapid cyclization to give 6-aminoperhydro-1,4-diazepine derivatives in excellent yields and with high selectivity, whereas the same reaction failed or gave negligible yields under conventional heating. Cesium or potassium ions catalyzed the ring closure by coordinating the sulfon-amide groups. All relevant work reported to date in the literature mostly concern about the syntheses of either 1H-tetrahydro-1,4-diazepine-2,5-dione or substituted 1,4-benzodiazepines, while the few published procedures for the preparation of 6-aminoperhydro-1,4- diazepines involved several steps, required long reaction times and afforded low yields. By the present method, access to 6-aminoperhydro-1,4-diazepines becomes much easier and faster.