UNUSUAL CHEMO-SELECTIVITIES AND STEREOSELECTIVITIES IN THE REACTIONS OF 1,2-DICHLOROCYCLOPROPENES WITH NITRILE OXIDES

1,2-Dichloro-3,3-dimethylcyclopropene reacts with a number of nitrile oxides to produce oxazines in moderate to good yield in a reaction whi ch apparently involves an unusual formal 3-centre plus 3-centre cycloa ddition of the dipole to an intermediate vinylcarbene. In contrast, 1, 2-dichloro-3-chloromethyl-3-methylcyclopropene undergoes a dipolar cyc loaddition to produce a 2-oxa-3-azabicyclo[3.1.0]-hex-3-ene in which t he 6-chloromethyl substituent occupies the endo-position.