2,4a, 5,6,7,8-Hexahydropyrido

Reactions of diphenylcyclopropenone with 2-alkyl-3,4,5,6-tetrahydro-pyridines and 2,3,4,4a,5,6,7,8-octahydroquinoline in an alcohol or in tert-butyl mercaptan afforded hexahydropyrido[2,l-fe][l,3]oxazines (171) and [l,3]oxazino[2,3- ]quinolines (172), respectively (86S899). 

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). 

The stereostructure of ethyl OT-4a,7-//-7-phenyl-8-cyano-2-oxo-2,3,4,4a,7,8-hexahydropyrido[l,2-A [l,2]oxazine-8-carboxylate was confirmed by X-ray crystallography. It confirmed a trans-nng junction <20000L4007>. The structure of 2,4-diphenyl-7-o-hydroxyphenyl-5,6-dihydropyrido[2,Ttf]phthalazinium perchlorate 21 has also been established by X-ray crystallographic analysis <1995IZV296>. 

Amino-6,6n,7,8,910-hexahydropyrido[2,l-c][l,4]benzoxazine was reacted with ethyl 4,4,4-trifluoroacetoacetate in boiling benzene for 12-16 h, then the reaction mixture was concentrated in vacuo and the residue was treated with cone. H2SO4 at 100°C to give tetracyclic 11-trifluoromethyl-l,2,3,4,4a,5,8,9-octahydropyrido[l, 2 4,5][l,4]oxazino[3,2-a]quinolin-9-one in 30% yield (OlMIPl). 

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