posted on 2017-11-28, 00:00authored byAlpa 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.