6,6a,7,8,9,10-Hexahydro-5//-pyrido

Reaction of l-(nitromethylene)perhydropyrido[l,2-c]pyrimidine with p-chlorobenzenesulfonyl azide in dioxane at 80°C gave the tricyclic 1-nitro-6,6a,7,8,9,10-hexahydro-5//-pyrido[l,2-c][l,2,3]thiazolo[l,5-a]pyrimidine [79JCS(P1)2361],... 

Catalytic hydrogenation of 5-oxy-7,8,9,10-tetrahydro-6a//-pyrido[l,2-a]quinoxalin-6-ylamines 352 over Pearlman s catalyst under 5 atm of H2 in MeOH for 5-7 days at room temperature gave 6,6u,7,8,9,10-hexahydro-5//-pyrido[ 1,2-u]quinoxalines (01EJOC987). 

Amino-3-chloro-5-trifluoromethylpyridine with electron-rich alkenes and formaldehyde in the presence of trifluoroacetic acid in boiling acetonitrile for 1 h yielded 6a,7,8,9,10,10a-hexahydro-6//-pyrido[l,2-a]-quinazolines (326) (96TL2615). The regiochemistry is dictated by the reaction of formaldehyde at the primary amino group. 

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