Hydroxymaleic anhydride

Reactions of 3-substituted 2-(lV-phenylaminomethyl)piperazines with a slight excess of ethyl 2-chloroacetate under reflux afforded mixtures of 9-substituted 2-phenylperhydropyrido[l,2-a]pyrazin-3- and -4-ones, which could be separated by column chromatography [72JCS(P2)1374], When 2-[(3-trifluoromethylphenyl)aminomethyl]piperidine was heated with optically active ethyl 2-chloropropionate (87MIP1 91TA231), or lactic acid ethyl ester methanesulphonate (91TA231), the product was a C-9a epimeric mixture of 2-(3-trifluoromethylphenyl)-4-methylperhydropyrido[l,2-fl]-pyrazin-3-ones. The reaction between yV-methyl-2-piperidine-carboxamide and hydroxymaleic anhydride in pyridine resulted in 2,3-dimethyl-3-hydroxyperhydropyrido[l,2-a]pyrazine-l,4-dione (74CB2804). 

The reaction of l,l-bis(trimethylsiloxy)ketene acetals with oxalyl chloride results in a straightforward one-pot s5mthesis of a variety of 3-hydroxymaleic anhydrides (eq 110). ... 

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