2- Phenyl-4,6,7,8,9,9«hexahydropyrido

Irradiation of piperidine 62 in CH2CI2 at concentration of 3mg/ml in the presence of 1-methylimidazole using a high-pressure mercury lamp (150 w) yielded 2-phenyl-4,6,7,8,9,9n-hexahydropyrido[2,l-h][l, 3]oxazin-4-one (01 SI258). 

Stereostructure of ethyl c/>4u,7-H-7-phenyl-8-cyano-2-oxo-2,3,4,4u,7,8-hexahydropyrido[l,2-6][l,2]oxazine-8-carboxylate was confirmed by X-ray analyses. It justified a trans ring junction of the bicycle (00OL4007). 

Michael addition of dialkyl cuprate reagents to optically active 4-phenyl-l,3,4,6,7,8-hexahydropyrido[2,l-c][l,4]oxazin-l-one afforded stereoselec-tively 9-alkylperhydro derivatives 228 in a mixture Et20 and THF at -40 °C in the presence of Cul in good yields (99TL3699). 

The asymmetric synthesis of (4R,93, 9aR)-4-phenyl-l-trimethylsilyloxy-9-vinylperhydropyrido[2,T ][l,4]oxazine with a high level of stereoselectivity in the cyclization of (3R,5R)-5-phenyl-3-phenylsulfanyl-4-(6-trimethylsilanyl-hex-4-enyl)-2-trimethylsilyloxy-morpholine was rationalized via AMI calculations <1998T10309>. AMI calculations suggested that the formation of l,6-dioxo-l,3,4,6,7,8-hexahydropyrido[2,Tf][l,4]oxazine-9-carboxylates 230 from acroyl chlorides 228 and 1,4-oxazinone 229 is favored over the hetero-Diels-Alder condensation (Equation 45) <1996JOC5736>. 

Diels-Alder reactions of (5.S )-5-phenyl-3,4-dehydromorpholin-2-one 388 with 1,3-butadienes 387 furnished (4.S, 9a,S )-/ra r-4,9a-//-4-phenyl-l,3,4,6,9,9a-hexahydropyrido[2,l-f][l,4]oxazin-6-ones 389 (Equation 70) <1996TA2563>. 

X-Ray crystallographic analysis of 4-(2,4-dinitrophenyl)-2,5-dioxo-8-phenyl-l,2,3,4,5,6-hexahydropyrido[2,3-pyrida-zine 7 is in agreement with the semi-empirical molecular orbital calculation (AMI) <2000T2473>. 

The methyl methylphosphonate quatemery salt 695 was patented as catalyst in curing of polyisocyanate (85GEP3328662). The 2-phenyl derivative of hexahydropyrido[l,2-a]pyrimidine (696) was patented as a catalyst for curing of blocked isocyanate-terminated polycarbonate (87EUP247692). Pyrido[l,2-a]pyrimidine-8-nitrile derivatives were... 

Diels-Alder reactions of (55)-5-phenyl-3,4-dehydromorpholin-2-one (210) with isoprene and 2,3-dimethyl-l,3-butadiene (209) furnished (45,9a5)-rrflns-4,9fl-H-4-phenyl-l,3,4,6,9,9fl-hexahydropyrido[2,l-c][l,4]ox-azin-6-ones (211) (96TA2563). 

Reaction of the enamino ester 224 with a,/3-unsaturated acyl chlorides 222 or anhydride 223 in boiling THF gave 4-phenyl-l,6-dioxo-l,3,4,6,7,8-hexahydropyrido-[2,l-c][l,4]oxazine-9-carboxylates (225) (95TL1657 ... 

An X-ray crystal structural determination revealed that the 8-carboxyl group of cij-4fl,8-H-l,3,4,4a,7,8-hexahydropyrido[l,2-c][l,3]oxazine-8-carboxylic acid is in a pseudoaxial position (81JA7573). The crystal structure of 4-phenyl-2- 4-[4-(2-pyrimidinyl)piperazin-l-yl]butyl -2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c][l,3]oxazine-l,3-dione was determined by an X-ray investigation (95ZK899). 

With 6-aminouracil, prop-2-ynal or 3-phenylprop-l-yn-3-one in aqueous alkali at 0°C reacts to furnish pyrido[2,3-phenyl derivative 232 similarly, methyl propiolate and l,3-dimethyl-6-aminouracil (33) in refluxing water give 1,3-dimethylpyrido[2,3-c/]pyrimidine-2,4,7(177,3//,8//)-trione (34).165 In protic media such as water or methanol, irrespective of the N1 substituent, the reaction with 6-aminouracils largely yields methyl 2,4,7-trioxo-l,2,3,4,7,8-hexahydropyrido[2,3-d]pyrimidine-5-carboxylates.I42,165,547,584... 

A partial aromatization of hexahydropyrido[4,3-potassium hexacyanoferrate(III).531 Starting from the hydrochloride of8-benzylidene-6-methyl-4-phenyI-3,4,5,6,7,8-hexahydropyrido[4,3-d]pyrimidine-2-thiol, after methylation of the sulfanyl group, the oxidation gives 8-benzylidene-2-(methylsuIfanyI)-6-methyl-4-phenyl-5,6,7,8-tetrahydropy-rido[4,3-d]pyrimidine. In a similar way, several 4-aryl-8-arylidene-6-methyl-3,4,5,6,7,8-hexahy-dropyrido[4,3-rf]pyrimidin-2-amines have been partially aromatized.513... 

Acetylation and benzoylation at N3 of the partially hydrogenated 8-benzylidene-6-methyl-4-phenyl-3,4,5,6,7,8-hexahydropyrido[4,3-r/]pyrimidin-2(l//)-one and -thione in 21-25% yield have been reported.511... 

Phenyl-4- [N,N-di(2-propyl)amino]ethyl perhydropyrido[l,2-c]pyrimi-dine-l,3-dione was obtained in the reaction of o -phenyl-a- [A,A-di(2-pro-pyl)amino]ethyl -2-piperidineacetamide and l,l -carbonyldiimidazole in the presence of sodium hydride (87USP4680295). 6-Dialkylamino-l,2,3,5,6,7-hexahydropyrido[3,2,l-y]quinazolin-3-ones were prepared via the reaction of 8-aminomethyl-3-(alkylamino)-l,2,3,4-tetrahydroquinoline and l,r-carbonyldiimidazole in THE (90MIP2 92JMC1076). 

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