1.4- Oxazines, synthesis from oximes

A novel synthesis of 5,6-dihydro-4//-1,2-oxazines (20) is presented via the photo-induced cyclization of y. d-unsaturated oximes (21) see Scheme 4. Irradiation of (21) in the presence of 9,10-dicyanoanthraccnc (DCA) led to the heterocycle (20) only. The proposed mechanism proceeds via the radical cation (22), generated by single-electron transfer (SET) from the oxime (21) to the excited sensitizer (DCA. Cyclization of (22) affords the oxazine (20) after proton transfer to the DCA radical anion (DCA ) and H abstraction.61... [Pg.145]

In addition to cyclic derivatives, this chemistry has also been used for the preparation of Q ,/3-unsaturated oximes from either nitroalkanes or 1,2-oxazine IV-oxides. Equation 27 shows the synthesis of /3-functionalized Q ,/3-unsaturated oximes from nitroalkanes. [Pg.95]

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