3.1- Benzoxazine, 4,4-dialkyl

Dialkyl N-(benzoxazin-4-yl)methylenemalonates and their optically active forms (1728) were prepared in the reaction of the appropriate pheny-laminomethylenemalonate (1727), triphenylphosphine, and diethyl azodi-carboxylate in THF at -20°C (89EUP3228I5). The hydroxyl group of racemic and optically active phenylaminomethylenemalonates (1727) were tosylated with p-toluenesulfonyl chloride in pyridine, and the products were cyclized by heating in DMF at 80°C in the presence of potassium carbonate and a catalytic amount of 18-crown-6-ether to give 1728 (89EUP322815). 

Aminobenzyl alcohols (298) give 4,4-dialkyl-4//-3,1 -benzoxazine derivatives (299) on treatment with acetic anhydride (1883CB2576). 

A similar construction of 2H- 1,3-benzoxazines employs salicylamide and dialkyl ketones the product benzoxazinones (166) can be converted into alkoxy (167 R = alkoxy) or chloro (167 R2 = Cl) derivatives by alkylation (32CB1032), or by treatment with phosphorus oxychloride (80CPB465) respectively (Scheme 58). 

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