1.4- Oxazines reduction

A fluorinated oxazine, prepared fromfluoroacetonitrile and 2 methyl-1,3-pen-tanediol, is alkylated at low temperature The resulting products furnish a fluoro aldehydes after botohydride reduction and hydrolysis [JJ4] (equation 99)... 

An interesting method for preparing 2,6-dioxo-l,3-oxazine derivatives was described by Wasserman and Koch who stated that the five-membered ring of an a-keto-lactam could be transformed into the 1,3-oxazine (22) by ozone followed by reduction with zinc. 

Reductive N-O bond cleavage of perhydropyrido[l,2-6][l,2]oxazine 10 with Zn dust furnished 2-(3-hydroxypentyl)piperidine 11 (96JCS(P1)1113). Similarly, 2/S,4u S,5Q ,7/0,8yS-H-5-benzyloxy-7-(tert-butyldiphenylsilyloxy)-2-[2-(methoxymethoxy)ethyl]-8-methylperhydropyrido[l,2-6][l,2]oxazine gave the respective ring-opened piperidine (OOOL2955, 01JOC3338). 

Reduction of the side chain keto group in 9-(2-oxobutyl)perhydropyr-ido[l,2-c][l,3]oxazin-l-ones 96 with NaBH4 in MeOH at ambient temperature afforded an epimeric mixtures of 9-(2-hydroxybutyl) derivatives 85 and 87 (96CJC2434). The epimers were separated by means of flash chromatography. 

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). 

Reduction of a perhydropyrido[l,2-c][l,4]oxazin-l-one with BH3 in anhydrous THF at room temperature yielded a perhydropyrido[l,2-c] [l,4]oxazine (OOMIPl). 

Treatment of 3-phenylperhydro[l, 3]oxazolo[3,2-a]pyridine-5-carboxylates 303 and 304 with BF3 Et20 in THE, followed by reduction with NaBD4 afforded 6-deutero-4-phenylperhydropyrido[2,1 -c][l, 4]oxazin-1 -ones 220 and 222 (97JA6446). 

The reductive acetylation of Brilliant Cresyl Blue (29) yields 1,9-dimethyl-4-acetamido-8-diethylaminoimidazophenoxazine (30) which gives a purple image in electrolytic recording.12 Other similar oxazine leucos (31-34) have also been developed for electrolytic recording.13 The leucos 33 and 34 produce blue violet images. 

As in the case of thiazine and oxazine leuco dyes described earlier, the reductive acylation of the phenazine dye 52 results in the acylation of the exocyclic amino group.18 The phenazine leuco obtained 53 retains the exocyclic amide group on oxidation resulting in the acylated phenazine dye 54, the color of which is different from the one intended. 

Reduction of 3-substituted-3,4,7,8-tetrahydro-l//,6//-pyrido[l,2-t][l,3 oxazin-l-ones with NaBHjCN in boiling MeOH, and with NaBH4 in AcOH, afforded 4a-epimeric mixtures of perhydro derivatives <2005T1595>. 

Treatment of 3-phenylperhydropyrido[ 1,2-/ 1,3 oxazin-l -one with LAH gave a 1 9.5 mixture of 3-phenylphenylper-hydropyrido[l,2-c][l,3]oxazine and l-methyl-2-(2-phenyl-2-hydroxyethyl)piperidine <20050BC520>. Reduction of ds- >,4a- I-/ra .v-8-H-3-incthyl-8-pentyIperhydropyrido[ 1 1,3 oxazin-6-onc with NaBH4 at room temperature... 

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