Perhydropyrido oxazine-3,4-dione

Treatment of perhydropyrido[2,l-c][l,4]oxazine-3,6-dione 232 with B2H6 yielded (—)-(2i )-[(2S)-hydroxymethyl)piperldin-1 -yl]-2-phenylethanol (233) (00T233). Reduction of ( )-(3i ,4i ,9aS)-4-methyl-3-phenylperhydropyr-ido[2,l-c][l,4]oxazin-3-ol (234) with NaBH4 yielded ring-opened product 235 (97JHC1813). 

Cyclization of the piperidone derivative (158) gave rise to diastereomer-ically pure perhydropyrido[2,l-h][l,3]oxazin-6-one (159) (94JA10819). Heating l-(3-methoxy-l-propyl)-2-hydroxy-3-cyano-4-methylpyridin-6(l//)-one in 25% sulfuric acid at 80°C for 2 h gave 8-methyl-6-oxo-2,3,4,6-tetrahydropyrido[2,1 -fo][ 1,3]oxazine-9-carboxamide (89EUP316779). 8-(4-Methoxyphenyl)-2,3,4,6-tetrahydropyrido[2, -b [1,3]oxazine-2,6-dione was obtained by cyclization of 3-[4-(4-methoxyphenyl)-2,6-dioxo-l,2,3,6-... 

Oxidation of frans-4(R)H,9(R)aH-8-methylene-perhydropyrido]2,l-c][l,4] oxazin-l-one with OSO4 and NaI04 in aqueous THF at ambient temperature provided frans-4(R)H,9a(R)H-perhydropyrido]2,l-c][l,4]oxazine-1,8-dione (08JOC6877). 

Perhydropyrido[2,l-c][l,4]oxazine-l,4-diones 299, 301, and 303 were obtained from piperidine derivatives 298, 300, and 302 stirring in MeOH saturated with HC1 gas overnight, but stereoisomer 304 gave only tarry material (07EJ03028). 

Cross double carbonylation of 2-hydroxymethylpiperidine in the presence of PdCl2(MeCN)2-CuI as catalyst under CO and 02 at ambient temperature in an autoclave afforded perhydropyrido[2,l-c][l,4]oxazine-3,4-dione [87JAP(K)87/212377,87JCS(CC)125],... 

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