Synthesis of 4,5-Diazaspiro[2.3]hexanes and 1,2-Diazaspiro[3.3]heptanes as Hexahydropyridazine Analogues
datasetposted on 2017-11-28, 00:00 authored by Alpa K. Pancholi, Greg P. Iacobini, Guy J. Clarkson, David W. Porter, Michael Shipman
4,5-Diazaspiro[2.3]hexanes are made by dihalocarbene addition across the exocyclic double bond of readily accessible 3-alkylidene-1,2-diazetidines. Using difluorocarbene, generated from TMSCF3/NaI, these spirocycles were produced in yields up to 97% by stereospecific addition across the alkene. Lower yields (up to 64%) were observed using more reactive dichlorocarbene, due to competitive insertion of the carbene into the N–N bond. Larger 1,2-diazaspiro[3.3]heptanes are produced by [2 + 2] cycloaddition of 3-alkylidene-1,2-diazetidines with tetracyanoethylene (TCNE) in up to 99% yield.