Reactions of Phthalazinecarboxylic Esters

Several reactions of these esters have been covered already reduction to alkylphthalazines (Section 9.2.1), reduction to extranuclear hydroxyphthalazines (Section 11.2.1), conversion into extranuclear hydroxyphthalazines with Grignard reagents (Section 11.2.1), conversion into aminophthalazines by the Curtius reaction reaction (Section 13.2.1), hydrolysis to phthalazinecarboxylic acids (Section 14.1.1), and transesterification (Section 14.3.1). Other reactions are illustrated in the following classified examples. 

This is usually done by hydrolysis and decarboxylation of the product, often in one pot, but hydrogenation has been used to remove A -alkoxy-carbonyl groups directly. 

2-(3-Ethoxycarbonyl-2-imino-5-methyltetrahydrofuran-3-yl)-l,4(2//,3fl)-phtha-lazinedione (47) gave 2-(5-methyl-2-oxotetrahydrofuran-3-yl)-l,4(2H,3//)-phthalazinedione (48) (3M NaOH, 20°C 93% note hydrolysis of the ester 

Benzyl 3-carbamoyl-l,2,3,4-tetrahydro-2-phthalazinecarboxylate (49) gave 1,2, 3,4-tetrahydro-2-phthalazinecarboxamide (50) (H2, Pd/C, MeOH, 20°C, 1 h 97% conformation by X-ray analysis). 

2-Ethoxycarbonylmethyl-4-methyl-l(2//)-phthalazinone (51, R=OEt) gave 2-carbamoylmethyl-4-methyl-l(2//)-phthalazinone (51, R = NH2) (NH4OH, reflux, 2h 50%) or 4-methyl-2-(phenylcarbamoyl)methyl-l(2/i)-phthalazi-none (51, R = NHPh) (neat PI1NH2, reflux, 2h 60%).  

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