Using 1,2-Dialkoxycarbonylbenzenes Phthalic Esters as Substrates

Such substrates have been used more widely than the two preceding types to give l,4(2//,3//)-phthalazinediones. Examples follow  

Dimethyl 4-amino-5-nitrophthalate (107) gave 6-amino-7-nitro-l,4(2H,37/)-phthalazinedione (108) (H2NNH2-H20, Et3N, MeOH, reflux, 2h 90%) analogs similarly.  

Dimethyl 3-hydroxy-6-methoxyphthalate (109) gave 5-hydroxy-8-methoxy-l,4(2H,3//)-phthalazinedione (110) (H2NNH2 H2O, EtOH, reflux, 12 h 84%) analogs likewise.  

In an unpredictable but interesting way, dimethyl phthalate (113, R = Me) with Af,AT-dimethyIhydrazine gave 2-methyl-l,4(2//,3//)-phthalazinedione (114) (neat reactants, —30°C, HeJ, then sealed 125°C, 18h 56%) plus gaseous products, identified as N2, CH4, MesN, and NH3 in contrast, similar treatment of diethyl phthalate (113, R = Et) gave a separable mixture of the same product (114) and 2,3-dimethyl-l,4(2//,3//)-phthalazinedione (115) (22% and 16%, respectively, plus N2, CH4, EtNMe2, and NH3 a mechanistic explanation was offered).  

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