A SOLID-STATE NMR-STUDY ON RING-CHAIN TAUTOMERISM IN 1,3-O,N-HETEROCYCLES

The solid-state C-13 CP/MAS NMR spectra of nineteen tetrahydrooxazines and oxazolidines have been recorded to determine their preferences fo r the ring or chain tautomeric form in the solid state. The chain form is preferred for those cases in wich <80% of the ring tautomer is fou nd in CDCl3 solution. The ring form is exclusively found only in deriv atives with <93% preference for the ring tautomer in solution. In one case the solid-state reaction converting the open chain to the ring wa s observed to take place over a time of several days.