436397.sch.002
Scheme 2: Synthesis of 7-N-substituted-1,3-oxazines 10-11 starting from 2-hydroxy-substituted benzoic acids 8 and 9. Reaction conditions: (i) compound a (Ac)2O, b PhCH=O, c 2-hydroxy-C6H4-CH=O, and d 3-ethoxy-2-hydroxy-C6H3-CH=O, (ii) Ph3P(SCN)2 in CH2Cl2, (iii) NaBH4, and (iv) Ph3P(SCN)2 in CH2Cl2.