Furo phthalazines

Furo[3,4-0]phthalazines (337, R = H, pj isv.isva j,ggjj obtained from the dicarbonyl compounds 336 (R = H,Ph). The phthalazine 337 (R = Ph) crystallizes as fine violet needles which fluoresce red in solution with maleic anhydride a Diels-Alder adduct is obtained in 99% yield. 

Furo[3,4-g]phthalazines and isobenzo[5,4-d]tropones have been prepared from 68 by similar condensation reactions [77TL1495, 79JCR(M)3518, 79JCR(S)302]. 

From Heteropolycyclic Derivatives as Substrates Furo- or Thieno[3,4- ]phthalazines as Substrates... 

Ethyl 8-amino- (26, R = NH2) underwent diazotization in fluoroboric acid to give ethyl 8-fluoro-l-hydroxymethyl-5,7-dimethyl-4-oxo-3,4-dihydro-6-phthalazinecarboxylate (26, R = F) [substrate, HBF4, H2O, 0°C, NaN02 in H20, 30 min solid. A, A, gasf 7%, after separation from the product of spontaneous cyclization, ethyl 4,6-dimethyl-3-oxo-2,3-dihydro-8//-furo[4,3,2-rie]phthalazine-5-carboxylate (26a) (31%)]." ... 

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