Quinazolines, dihydro-, synthesis

H- Isoxazolo[3,2-fc]quinazolin-9-one, 2,3-dihydro-synthesis, 6, 632 Isoxazolo[3,4-c]quinoline synthesis... 

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). 

The 2,3-dihydro-6/7-pyrimido[2,l-A]quinazolin-4(177)-ones 201 were obtained in a one-pot synthesis from the iminophosphorane 199 and isocyanate, through the 2-aminoquinazoline 200. Yields were good (R1 = H, Rz = c-hexyl) to excellent (R1 = Rz = Ph) (Equation 21) <1996TL9071>. 

In the United States, compound RGW-2938 (47) has been developed as a selective positive inotropic agent its synthesis and pharmacological actions have been reviewed [161]. Related compounds, in which the dihydro-pyridazinone system is replaced by a benzoxazinyl system instead of the quinazoline system, have recently been studied in India and in the United States [162,163]. From this series, bemoradan (48) was found to be a very potent orally active, long-acting inotropic vasodilator agent in canine models (i.v. ED5o = 5.4 //g/kg 24h duration of action) [163]. 

Kumar, R.R. and Reddy, M.S., One-pot synthesis of 2,3-dihydro-2,3-disubstituted benzo[g]quinazolin-4(lH)-ones, Synth. Commuru, 1992, 22, 2499-2508. 

Devi, R.R. and Reddy M.S., Synthesis of 6,7-dihydro-6-substituted benzimidazo [ 1,2-c Jbenzo [y ] quinazolines and their heteroaromatic analogues, Indian J. Chem. 1994, 33B, 1013-1016. 

A highly effective method has been proposed for the synthesis of 6,12-dihydro-6,12-dioxoindolo[2,l-h]-quinazoline (179) - the alkaloid couropitine A (from the tropical tree Couropita guianensis), having the same structure as the antibiotic tryptanthrin (from the yeast Candida lipolytica Hegolus), by the reaction of isatin with phosphorus oxychloride followed by treatment of the reaction mixture with ice [198] ... 

Azole approach. A one-pot synthesis of substituted 2,3-dihydro-5-oxo-5H-oxazolo[2,3-b ]quinazolines (273) consists of reacting esters of anthranilic acid with a 2-chloro- or 2-bromoalkyl-isocyanate the initially formed urea (271) is cyclized to the acid salt of the oxazoline (272), which on addition of piperidine as base forms the pyrimidine ring (76S469). In a similar reaction the aziridinyl urea (274), which is available from aziridinyl isocyanate... 

Amidines 9 with an appropriate ortho-carbonyl substituent, which are obtained from the respective ortho-carbonyl aniline derivatives and 0-ethyl succinimide (5-ethoxy-4,5-dihydro-3//-pyrrol-2-one), are cyclized with sodium in alcohol to quinazolin-4(3// )-ones 10a and quinazolines 10b with a 2-[(alkoxycarbonyl)ethyl] substituent at C2. The reaction can also be carried out starting from anthranilates or 2-aminophenyl ketones as a simple one-pot synthesis. ... 

A general synthesis of quinazoline 1,3-dioxides and their 1,2-dihydro derivatives was devised by Taylor and Bartulin. In this synthesis o-hydroxyl-aminobenzaldehyde oxime condensed with aldehydes and ketones to yield 2,2-disubstituted 1,2-dihydro-l-hydroxyquinazoline 3-oxides (63). When the dihydro compounds (63 = H) derived from aldehydes or from formalde-... 

Many ring-fused imidazole derivatives have been synthesized by various methods. Domino Michael addition retro-ene reaction of 2-alkoxyiminoimidazolidines and acetylene carboxylates provided a synthesis of 2,3-dihydroimidazo[l,2-a]pyrimidin-5-(l//)-ones <05T5303>. A single step synthesis of 3,5-dialkyl-9-nitroimidazo[l,2-c]quinazolin-2(3//)-ones from simple carbonyl compounds, primary amines or amino acid methyl esters and 2-azido-5-nitrobenzonitrile has been published <05TL5778>. Diels-Alder reaction of azadienes and benzimidazole-4,7-diones afforded imidazo[4,5-g ]quinoline-4,9-dione derivatives <05EJ01903>. Reaction between isocyanides and dialkyl acetylenedicarboxylates in the presence of 4,5-diphenyl-l,3-dihydro-2//-imidazol-2-one provided a one-pot synthesis of 5//-imidazo[2,l-ft][l,3]oxazine derivatives <05T2645>. Microwave irradiation was employed in the synthesis of 1-ary 1-3-acetyl-1,4,5,6-... 

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