A new method has been developed to synthesis spiro-substituted benzo[b]furo[3,4-e][1,4]diazepene derivatives in one step, forming two spiro rings and five σ bonds in the process.
This chemo- and regioselective [4+2+1] domino cyclization reaction was discovered by scientists from Xuzhou Normal University, China and Texas Tech University, USA. The synthesis of heterocyclic compounds with quaternary carbon centres is important as these compounds are useful intermediates in organic synthesis and are often biologically active.
The procedure developed here is performed in water with microwave irradiation and uses easily available and cheap starting materials. This one-pot reaction can be performed in 10-18 minutes with reduced waste production and without the use of any strong acids or metal promoters. In addition, recrystallization and chromatography purification procedures can be avoided as the pure products can be obtained by simply washing the crude product with 95% ethanol.
The authors feel this will serve as a nice addition to Group-Assistant Purification chemistry.
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[4+2+1] Domino cyclization in water for chemo- and regioselective synthesis of spiro-substituted benzo[b]furo[3,4-e][1,4]diazepine derivatives, Chuang Cheng, Bo Jiang, Shu-Jiang Tu and Guigen Li, Green Chem., 2011, DOI: 10.1039/C1GC15183E