Oxazines methyl-nitro

Nitrones or aci-nitro esters react with alkenes to give in some cases A/-substituted isoxazolidines and in others 2-isoxazolines. When the intermediate isoxazolidines were observed, a number of procedures transformed them into the 2-isoxazolines. Acrylonitrile and phenyl rzcf-nitrone esters produced an A/-methoxyisoxazolidine. Treatment with acid generated a 2-isoxazole while treatment with base generated an oxazine (Scheme 118) (68ZOR236). When an ethoxycarbonyl nitrone ester was reacted with alkenes, no intermediate isoxazolidine was observed, only A -isoxazolines. Other aci-mtro methyl esters used are shown in Scheme 118 and these generate IV-methoxyisoxazolidines or A -isoxazolines which can be further transformed (72MI41605). 

H-1,2-Oxazine, 3,6-dihydro-6-(2-pyridyl)-mass spectra, 2, 529 2H-1,2-Oxazine, tetrahydro-synthesis, 2, 92 4H-l,2-Oxazine, 5,6-dihydro-pyrolysis, 3, 999 synthesis, 3, 1017 tautomerism, 3, 999 4H-1,2-Oxazine, 5,6-dihydro-3-methyl-metallation, 1, 484 4H-l,2-Oxazine, 5,6-dihydro-3-nitro-reactions, 3, 1000 6H-l,2-Oxazine, 3,5-diphenyl-stability, 3, 997 synthesis, 3, 1014... 

Interestingly, Allingham et al. (66) have analyzed a series of N-alkyl 5-nitrotetrahydro 1,3-oxazines and concluded that there is a preference for the N-alkyl axial conformer U)l when the alkyl substituent is methyl, ethyl or propyl and a preference for the N-alkyl equatorial conformer 102 when the substituent is isopropyl, cyclohexyl or t-butyl. Thus, J01 is still preferred despite the 1,3-diaxial steric interaction between the nitro group and a primary N-alkyl group. Finally, Katritzky et al (70) have proposed the conformation 103 as the major one for compounds 104 and 105,... 

Amino-7-oxo-2,3-dihydro-7H-pyrido[l,2,3-de][l,4]oxazine-6-carbox-ylic acids were obtained from 8-(4-methoxyphenyl)amino derivatives by treatment with TFA at room temperature in CH2CI2, and 8-amino-3-esters from 8-benzylamino- and 8-nitro-3-ester derivatives by catalytic hydrogenation over Pd/C catalyst in acidified EtOH and DMF in 60% and 87% yields, respectively (07WOP2007/106537). The nitro group of 8-nitro-9,10-difluoro-3(S)-methyl-7-oxo-2,3-dihydro-7H-pyrido[l,2,3-de][l,4]oxazine-6-carboxylic amide was reduced with Na2S204 in a suspension in boiling aqueous EtOH for 5-8 h. 

Tetrahydro-l,3-oxazin 3-Ethyl-5-(l-methyl-5-nitro-imidazol-2-yl-methyl)-5-nitro- E14a/2, 712 [C = NOf C(N02)-C]... 

Oxazin 5-Methyl-3-(4-methyl-benzyl)-5-nitro-tetrahydro-E14a/2, 711 (l,3-Diol/CH20/ R-NH2)... 

The preparation of all four mononitro aromatic derivatives of 1,2-benzisothiazol-3-one S,S-dioxide was reported. As an example, the preparation of the 5-nitrosaccharin 314 Method 0) from nitro-lH-benzo[d][l,3] oxazine-2,4-dione 312 is outlined in the Scheme 76. Starting from 312, which was treated with K2CO3 in MeOH, the methyl 2-amino-5-nitrobenzoate 313 was formed. The amino group was transformed into the diazonium salt (NaN02 in AcOH/HCl). Its reaction with CuCh and sulphur dioxide afforded the corresponding sulfonyl chloride, which was added to cold concentrated ammonium hydroxide and 314 was isolated in 74% yield [lOOj. 

Dioxo-3-ethyl-l, 5,6,7-tetrahydro- 677 Pyrazolo[3,4-d]-l, 3-oxazin l,3-Dimethyl-4-oxo-6-(2-oxo-propyl)-dihydro- 557 1- Acyl-3-methylthio-6-oxo-l,6-dihydro- 676 2- Benzyl-6-(4-nitro-phenyl)-4-oxo-2,4-dihydro-676 4-Amino-7-chlor-phenyl- 976 2-(4-Aminosulfonyl-phenyl)-4,7-dichIor- 977 2-(4-Aminosulfonyl-phcnyl)-4,7-dihydroxy- 922 4-Anilino-7-chlor-2-(3-thienyl)- aus 4,7-DichIor-2-(3-thicnyI)- pyriclazino-[4,5-d]-l,3-thia7.ol)/Ethanol 976 7-Chlor-4-ethoxy-2-methyl- 972 7-Chlor-4-methoxy-2-phenyl- 972 7-ChIor-4-(3-pyrroIidino-propyloxy)-2-(2-thienyI)- 972... 

Pyrrolidinocyclohexene added drop wise at 0° under Ng (maintained throughout the reaction) during a few min. to a soln. of 2-nitro-l-phenylpropene in dry hexane, then allowed to warm to troom temp., and the product isolated after 2 hrs. -> 3-methyl-4-phenyl-8a-pyrrolidino-4a, 5,6,7,8,8a-hexahydro-4H-l, 2-benz-oxazine 2-oxide. Y 91%. F. e. s. A. T. Nielsen and T. G. Archibald, Tetrahedron 26, 3475 (1970). 

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