Pyrazolo-quinazolines

Cycloaddition of 4-phenyl-1,2,3-benzotriazine (94) to diphenylcyclo-propenone gave, among other products, the pyrazolo[l,5-a]quinazoline (95) (80CC808). 

Synthesis from quinazoline precursors was achieved by carrying out a Vilsmeier-Haack reaction on 3-amino-2-methyl-4-quinazolone (96) to give the intermediate diformyl derivative 97 that cyclized to 3-formylpyra-zolo[5,l-b]-quinazolin-9-one (98) [73IJC532 84IJC(B)161]. 

Formation of both heterocyclic rings of 104 was accomplished upon reaction of acetonylbenzoxainones (103) with hydrazine (62GEP1139123). 

Cyclization of 3-(2-aminophenyl)pyrazoles (108) with triethyl orthofor-mate [62AG249 67USP3313815 80GEP(0)3019019), phosgene 

Reaction of 2-isothiocyanato-/ra/w-cinnamaldehyde (110) with hydrazine gave the pyrazolo[l,5-c]quinazolines (111), presumably via the corresponding hydrazone and conjugate addition to the pyrazoline followed by cyclization [76JCS(P1)653]. 

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Annulation with heterocyclo-quinazolines 7.3.1 Synthesis of pyrazolo-quinazolines... 

Some tricyclic systems have been prepared by intramolecular cyclization from A-aryl-pyrazoles carrying substituents both in the pyrazole ring at C-5 and in the phenyl ring at the o-position. Thus pyrazolo[l,5-n]quinazolines (563) (69JHC947) and pyrazolo[l,5-n]-[l,4]benzodiazepines (564) (77JHC1163, 77JHC1171) can be prepared from suitable precursors. 

Pyrazolopyrimidinones C NMR, 5, 308 methylation, 5, 310 synthesis, 5, 329 Pyrazolopyrimidinones, thioxo-synthesis, 5, 324 Pyrazoloquinazolines synthesis, 5, 317, 322 Pyrazolo[ 1,5-n]quinazolines synthesis, 5, 273 Pyrazolo[ 1,5-c]quinazolines synthesis, 5, 324 Pyrazolo[2,3-n]quinazolines synthesis, 3, 378 Pyrazoloquinazolinones synthesis, 5, 342 Pyrazolo[4,3-/]quinazolinones synthesis, 5, 273 Pyrazolo[4,3-g]quinazolinones synthesis, 5, 273 Pyrazolo[3,4-/]quinolines synthesis, 5, 273 Pyrazolo[4,3-/]quinolines synthesis, 5, 273 Pyrazolo[l,5-n]quinoxalines synthesis, 5, 339 Pyrazolo[3,4-6]quinoxalines synthesis, 5, 272... 

Reactions which can be considered as cycloadditions are rare in the 1,2,3-triazine field. 4-Substituted 1,2,3-benzotriazines (2) react with diphenylcyclopropenone to give one, two or three of the following products pyrazolo[l,2-a][l,2,3]benzotriazin-l-ones (69), pyrazolo[l,2-a][l,2,3]benzotriazin-3-ones (70) or pyrazolo[2,3-a ]quinazolines (71) (80CC808). 

Diazoxindole (305) adds DMAD to give 83% of the pyrazolo[l,5-c]quinazoline (307), presumably via 306.188... 

Alternatively, (217) react with activated methylene synthons in the presence of potassium bicarbonate to afford transient C=N adducts (218) which revert to the 4-amino-5-(/ ,/ -di substituted vinyl)triazoles (219) or (220). Recyclization of these products (219) or (220) affords (215). Similar transformations of l-substituted-l/7-pyrazolo[3,4-J]pyrimidines (77CPB535), pyrido[2,3-t/]py-rimidines (75CPB2939, 78CPB3242), and quinazolines <79CPB286l> have also been reported. 

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