3- Phenyl-6,7,8,9-tetrahydro-47/-pyrido

A sulfoxide was obtained by oxidation of 8-[(4-trifluoromethylmercapto-phenyl)methoxy] derivative 358 with 36% H2O2 in AcOH (98MIP7) and by oxidation of l-[2-(4-thiomorfolin-l-yl)acetyl]-7-(3-methoxyphenyl)-A-methyl-A- [3,5-bis(trifluoromethyl)phenyl]ethyl -5-oxo-1,2,3,5-tetrahydro-pyrido[l,2,3-i/ ]quinoxaline-6-carboxamide with 3-chloroperbenzoic acid (01MIP12). A 7-[(4-fluorophenylsulfonyl)methyl] derivative was obtained by oxidation of a 7-[(4-fluorophenylsulfanyl)methyl]perhydropyrido[l,2-u] prazine with 3-chloroperbenzoic acid in CHCI3 (01EUP1074257). 

Reduction of 2-methyl-4-phenyl-3//-pyrido[l,2-Z)]pyridazin-3-one (44) with NaBH4 in ethanol afforded the 5,6,7,8-tetrahydro derivative [76JCS(CC)275 78JOC2892],... 

Hexahydro-l,3-diazepin-2-thione may be conveniently converted into the iV,iV -dialkyl-hexa-hydro-l,3-diazepin-2-one by treatment with alkyl halides in the presence of aqueous sodium hydroxide and a catalytic amount of benzyltriethylammonium chloride <82S464> and its reaction with (2-bromo-1 -phenylethylidene)malononitrile affords 7-amino-8-cyano-9-phenyl-2,3,4,5-tetrahydro-pyrido[ 1,2-a][l, 3]diazepine <90JOC4740>. 

When 3-phenyl-3//-triazolo[4,5-/]quinoline was heated at 390 00°C, IH-pyrido[2,3-c]carbazole 149 originated. Its structure could be confirmed by unambiguous synthesis from the 8,9,10,1 l-tetrahydro-7//-pyrido[2,3-c]carbazole (52CJC711). 

The relative stereostructure of 9-acetyl-7-hydroxy-l,2-dimethyl-7-meth-oxycarbonyl-4-phenyl-6-oxo-l, 4,7,8-tetrahydro-6/7-pyrido[l, 2-u]pyri-midine-3-carboxylate 122 was justified by an X-ray diffraction analysis (97JOC3109). The stereochemistry and solid state structure of racemic trans-6,9-//-l, 6-dimethyl-9 z-ethoxy-9-hydroxy-4-oxo-l,6,7,8,9,9 z-hexahydro-4//-pyrido[l,2- z]pyrimidine-3-carboxylate (123), adopting a cw-fused conformation, were determined by X-ray investigations (97H(45)2175). 

Reaction of 1,3-propanediamine and 3-cyano-4-methyl-6-methylthio-l-phenyl-2-0X0-],2-dihydropyridine-5-carboxylate 385 yielded 7-cyano-8-methyl-6-oxo-],2,3,4-tetrahydro-6/7-pyrido[],2-a]pyrimidine-9-carboxylate (386) (94JHC393). 

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... 

Tetrahydropyrido[2,1 -HI 1,4 oxazinc-7,9-dicarboxylate 278 was obtained from the 1,8-dihydro derivative 277 by hydrogenation over a Pd/C catalyst (Equation 51) <1997CAP2188071 >. Catalytic hydrogenation of an epimeric mixture of (4.S, 9a.S )-l -trimcthylsilyloxy-4-phenyl-3,4,6,7-tetrahydro-l//-pyrido[2,1 -HIl,4]oxazine over Raney-Ni afforded perhydro derivatives <2000SC2565>. 

Mild acidic hydrolysis of amino nitrile 369 gave m-4,9a-/7-rra r-9-7/-9-benzyloxy-4-phenyl-3,4,9,9a-tetrahydro-17/,67/-pyrido[2,l-d[l,4]oxazin-l-one <1996TL4001>. (2A)-2-Cyano-l-[(lR)-2-hydroxy-l-phenylethyl]piperidin-6-one, on standing for 20 days in ethanol saturated with HC1 gas, afforded (4/ ,9aA)-4-phenylperhydropyrido[l,2-4[l,4]oxazine-l,6-dione, which was sometimes accompanied by the unstable (26 )-l-[(l/ )-2-hydroxy-l-phenylethyl]-... 

Thermolysis of 3-alkyloxy- and 3-aroyloxy-5-phenyl-l,2,4-pyrrolo[l,2- ]quinoxaline-l,2,4-triones afforded 5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-6,8,10-trioxo-5,6,9,10-tetrahydro-87/-pyrido[l,2-tf ]quinoxaline-7,9-dicarboxylates <2000CHE615, 2004CHE1295> and 7-aroyl-8-aroyloxy-5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-5,6-dihydro-1077-pyrido[l,2- ]quinoxaline-6,10-diones <2002CHE498>, respectively. Thermolysis of 3-aryl-2-(5-aryl-2,3-dioxo-2,3-dioxo-4-furanyl)quinoxalines gave 7-aroyl-8-aroyloxy-6-aryl-9-(3-aryl-2-quinoxalyl)-10/7-pyrido[l,2- ]quinoxalin-10-ones <2001CHE1314, 2002RCB850>. 

Reaction of 3-formyM/7-pyrido[ 1,2- ]pyrimidin-l-ones with hydroxylamine O-sulfonic acid at 5 °C, then 50 °C yielded 3-nitriles <2003T4113>. Treatment of 2-hydroxy-3-(dimethylamono)methyF4//-pyrido[l,2- ]pyrimidin-4-one with Mel, then with KCN gave the 3-cyanomethyl derivative <2004MI215>. A condensation product was obtained from 5-amino-l-ethyl-6-hydroxy-l,3-dihydrobenzimidazol-2-one and 3-lbrmyl-2-hydroxyA//-pyndo[ 1,2- ]pynmidin-l-one <2002W002/38549>. l-(2-Aminopyrimidin-4-yl)-8-phenyl-l,2,3,4-tetrahydro-6//-pyrido[l,2- ]pyrimidin-6-ones were prepared from l-(2-methylthiopyrimidin l-yl)-8-phenyl-l,2,3,4-tetrahydro-6//-pyrido[l,2- ]pyrimidin-6-one by treatment with MCPBA, and then with aralkylamines <2005W005/070932>. 

The reaction of 2-phenyl-5(4//)-oxazolone (150) and 3-[( )-2-N,N-dimethylaminoethenyljpyridazine (149) in boiling acetic acid afforded 7-benzamido-8//-pyrido[l,2-b]pyridazin-8-one (151) (91BSB533). Treatment of dianion 152 with 1,4-dichlorobutane at -78°C gave 7,llh-diphenyl-2,3,4,llh-tetrahydro-l//-pyrido[2,l-fl]phthalazine (153) (86JHC13). 

Bismethylthio)methylene]- and 6-[(methylthio)(phenylamino)meth-ylene]- derivatives of 6,7,8,9-Tetrahydro-117/-pyrido[2,l-6]quinazolin-ll-ones (125 and 126) were obtained from 6,7,8,9-tetrahydro-l 1 //-pyrido[2,l-b]quinazolin-ll-one (7) with carbon disulfide and phenyl isothiocyanate, respectively, in dimethylsulfoxide in the presence of sodium hydride, and then methylation with methyl iodide (86ZC251). 

Cycloaddition of phenyl isocyanate and 2,3,4,4a-tetrahydro-l//-pyrido[l,2-a]quinazoline-./V-oxides (143) in benzene for 15 min afforded tetracyclic compounds (144) [90AP(323)405 92ZN(B)1333]. 

Cyclization of 1 -(4-chlorobutyryl)-l, 2-dihydro-4-phenylquinazoline-2-carbonitrile (242) in dimethylformamide in the presence of sodium hydride (80%) overnight gave 4a-cyano-6-phenyl-2,3,4,4a-tetrahydro-l//-pyrido[l,2- ]quinazolin-l-one (243) [86JCS(P1)2295]. Treatment of l-(2,6-dioxopiperidino)-2-azidomethylbenzene with triphenylphosphine in xylene at ambient temperature followed by heating to reflux for 2 h gave 2,3,4,6-tetrahydro-l//-pyrido[l,2-c]quinazolin-l-one in 92% yield [89JCS(CC)602]. 

Dipolar cycloaddition of anhydro pyrido[2,l-b][l,3]thiazinium hydroxides (128) with aryl isocyanates and dimethyl acetylenedicarboxylate gave pyrido[l,2]pyrimidines (129) and quinolizine-l,2-dicarboxylates (130), respectively (76CB3668). 1,4-Dipolar cycloaddition of pyrido[2,l-h][l,3]thi-azinium betaine (131, R = Me) with 1-diethylamino-l-propyne afforded cycloadduct 132, from which quinolizin-4-one 133 formed by a rapid cheletropic extrusion of carbonyl sulfide (93TL5405 95T6651). 1,4-Dipolar cycloaddition of anhydro 4-hydroxyl-2-oxo-6,7,8,9-tetrahydro-2//-pyrido-[2,l-b][l,3]thiazinium hydroxides (131) and 4-phenyl-l,2,4-triazoline-3,5-dione yielded 135 via 134 [94H(39)219 95H(41)1631] and 136 (95T6651). 

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