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Paper | Regular issue | Vol 81, No. 4, 2010, pp.955-964
Published online, 12th February, 2010
DOI: 10.3987/COM-10-11905
A Short and Convenient Synthesis of Novel Thienopyrazolodiazepine and Thienopyrazoloxazepine Skeletons via Nitrilimine Cycloaddition

Giorgio Molteni* and Paola Del Buttero

*Department of Organic and Industrial Chemistry, University of Milano, Via Golgi 19, 20133 Milano, Italy

Abstract

Silver carbonate treatment of 3-thenyl-substituted hydrazonoyl chloride (3) promoted the in situ generation of the corresponding nitrilimine (4) which constitute the key intermediate in the three step synthesis of both thieno[2,3-f]pyrazolo[1,5-a][1,4]diazepine and thieno[2,3-f]pyrazolo[1,5-a][1,4]oxazepine skeletons. The concurrent formation of unusual pyridazine derivatives arising from the electrophilic attack of a nitrilium cation to the carbon-carbon double bond is also discussed in some detail.