Quinazoline tetrahydro

The least troublesome routes to 3,4-dihydro- and 1,2,3,4-tetrahydro-quinazoline are probably the reduction of quinazoline by sodium borohydride, in water for the former or in methanol for the latter. Both must be isolated as salts. The dihydroquinazoline may be formed also by reduction with LAH in ether (65JHC157). In contrast, 5,6,7,8-tetrahy-droquinazoline is best made by primary synthesis from 2-formylcyclohexanone and for-mamide (57CB942) or from cyclohexanone and trisformamidomethane (60CB1402). 

Quinazoline, 1,2,3,4-tetrahydro-synthesis, 3, 108, 124 Quinazoline, 5,6,7,8-tetrahydro-synthesis, 3, 116 Quinazoline alkaloids occurrence, 3, 148 Quinazolinecarbonitriles hydrolysisj 3, 83 Quinazoline-2-carbonitriles reactions... 

IR Spectra of the hydrochloride of 6,7,8,9-tetrahydro-l l//-pyrido[2,l-Z)]quinazolines and their ZnCli complexes were investigated in the stretching vibration region of N" " (2000-3500 cm ) (97MI18, 99MI25). 

Condensation of 6,7,8,9-tetrahydro-l]/f-pyrido[2,]-6]quinazolin-ll-one and PhCHO in boiling AC2O for 48 h yielded a 6-phenylmethylene derivative (01H(55)1555). 

Cyclization of 2-(4-hydroxypentyl)quinazolin-4(3//)-ones 422 under Mitsunobu s conditions afforded only linearly fused 6,7,8,9-tetrahydro-1 l/f-pyrido[2,l-6]quinazolin-l l-ones 423 without angularly fused 1,2,3,4-tetrahydro-6//-pyrido[l, 2-n]quinazolin-6-ones 424 (98CPB928). 

Oxidative cyclization of 1 -[(2 -aminocarbonyl)phenyl]piperidine and its 4 -substituted derivatives with Hg(OAc)2-EDTA reagent afforded 1,2,3,4-tet-rahydro-6//-pyrido[2,l-Z)]quinazolin-6-one and its 3-substituted derivatives in 36-82% yields (99ZN(B)1577). Similarly, ( )-2-(piperidin-2-yl)benzal-doximes gave 2,3,4,4u-tetrahydro-l//-pyrido[l,2-u]quinazolin-5-oxide and... 

Reaction of 1 -methylene-1,2,3,4-tetrahydro-5//-pyrazino[2,1 -Z)]quina-zoline-3,6-diones (435) with PhLi and MeMgBr in THE at —78°C gave a mixture of 1 l//-pyrido[2,l-Z)]-quinazolin-l 1-ones 435-439 (01T1987). 

Reduction of 2,3,6,7-tetrahydro-177,5i/-pyrido[3,2,l-//]quinazoline-l,3,7-trione and 7-chloro-6-formyl-2,3-dihydro-177,5i/-pyrido[3,2,1 -(/]quinazo-line-l,3-dione with NaBH4 in THF in the presence of 60% aqueous solution of NaOH gave 7-hydroxy and 7-chloro-6-hydroxymethyl derivatives, respectively (01MI28). 

Vilsmeyer-Haack formylation of 7-hydroxy-2,3,6,7-tetrahydro-l//,5//-pyrido[3,2,l-y]quinazoline-l,3-dione with POCI3/DMF gave 7-chloro-6-formyl-2,3-dihydro-l//,5// derivative. Boiling a toluene solution of the aforementioned 7-hydroxy derivative in the presence of pTSA yielded dehydrated 2,3-dihydro derivative (01MI28). 

Tetrahydro-l//,5//-pyrido[3,2,l-//]quinazoline-l,3-diones were prepared by the cyclization of l-tert-butoxycarbonyl-l,2,3,4-tetrahydroqui-noline-8-carboxamide on the action of 60% aqueous NaOH solution in THF at 50 °C (01M128). 

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