The title reactions yield labile 4,5-dihydro-1,3-oxazole-4-spiro-2'-th
iiranes 4 which isomerize in solution to the thietan-3-imines 5. This
isomerization also occurs when the spiro compounds are heated to their
melting points, but here the desulfurized products 8 and 9 are also f
ormed in some cases. These are also the products obtained by SO2 extru
sion of the sulfones 10 derived from 5.