Zj. Wang et al., Syntheses and structure elucidation of dimethylaminovinyl substituted 1,3-oxazines and pyrazolo[3,4-d][3,1]oxazine derivatives, HETEROCYCLE, 51(12), 1999, pp. 2893-2905
Potassium methyl dicyanoacetate (1) reacted with (3,3-dichloro-2-propenylid
ene)dimethylammonium chloride (2) to yield a mixture (1:1) of E- and Z-4-ch
loro-5-cyano-2 -(N, N-dimethylimmonio)ethyliden-6-oxido-1,3-oxazines (3) wh
ich reacted further with different amines and arylhydrazines to 1,3-oxazine
and pyrazolo[3,4-d][3,1]oxazine derivatives respectively. The products exi
st surprisingly only as E- configuration. The structures were elucidated un
ambiguously with a X-Ray diffraction analysis and NMR experiments.