Oxazine double ring opening

Allylic displacements. Ring opening of perhydro-iV-tosyl-2-allyl-l,3-oxazines with Grignard reagents leads to enamine derivatives. Temperature dependence of the double bond configuration is remarkable. Allylic carbamates furnish predominantly fZl-alkenes. ... 

Malononitrile and similar active acetonitriles combine with 3,5-bis(2,4-cyclohexadien-l-on-6-ylidene)-l,2,4-dithiazolidine (229) to yield dicyanomethylene-l,3-benzoxazines (231). Presumably intermediates (230) are formed through addition of the malononitrile to the exocyclic double bond at C-3 of the dithiazolidine, allowing in turn ring-opening, aromatization of the 1,2-quinonemethide ring, cyclization to the oxazine unit, and finally loss of hydrogen sulfide plus sulfur (Scheme 63) <85S535>. 

N,N-Betaines s. Aminimides Betti 1,3-oxazine ring closure 10, 578 22, 778 Bi... s. a. Di... Bicyclo[1.1.0]butane ring opening, double -, diene synthesis with - 31, 654 Bicyclo[5.3.0]decane ring s. Azulenes... 

Tetrahydro-l,2-oxazin-3-one ring opening Hydrogenation of carhon-carhon double bonds... 

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