A Convenient One-Pot Synthesis of 4-Substituted 3,5-Bis(alkoxycarbonyl) -4,5-dihydroisoxazole 2-Oxides from Aldehydes and Nitroacetic Esters in a Solid-Liquid Reaction System and Subsequent Deoxygenation
Synthetic and mechanistic aspects of 4-substituted-3,5-bis(methoxy-carbonyl)isoxazoline N-oxides and the corresponding 3,5-bis-(butylcarbamoyl)isoxazoles derived therefrom.
作者:EISUKE KAJI、SHONOSUKE ZEN
DOI:10.1248/cpb.28.479
日期:——
An improved method for the synthesis of 4-substituted-3, 5-bis (methoxycarbonyl)-isoxazoline N-oxides (3) was developed by one-step cyclization of aldehydes with methyl nitroacetate in N, N-dimethylacetamide. The reaction mechanism was found to involve intramolecular nitrite ion displacement by the nitronate anion (9) ; this was confirmed by the formation of 3, 5-bis (methoxycarbonyl)-4-phenylisoxazoline N-oxide-4-d (11), starting from benzaldehyde-1-d and methyl nitroacetate. Conversion of isoxazoline N-oxides (3) to the corresponding 3, 5-bis (butylcarbamoyl) isoxazoles (7) is also discussed.
Synthetic Reactions of Isoxazoline 2-oxides. Part XIV. New Route to 1,3,3a,8a-Tetrahydro-2H-benzofuro(2,3-b)pyrrol-2-ones from Methyl .ALPHA.-Hydroxy-4H-1,2-benzoxazine-4-acetates Obtained by Ring Transformation of 4-Aryl-2-isoxazoline 2-Oxides.
作者:Kazuho HARADA、Eisuke KAJI、Kiyobumi TAKAHASHI、Shonosuke ZEN
DOI:10.1248/cpb.42.1562
日期:——
4-Aryl-2-isoxazoline 2-oxides (1) were converted to methyl α-hydroxy-3-methoxycarbonyl-4H-1, 2-benzoxazine-4-acetates (3) upon treatment with a Lewis acid such as titanium tetrachloride. The structure of 3 was confirmed by X-ray analysis. Tosylates of 3 were treated with triethylamine to yield (E)- and (Z)- isomers of olefins (5) with (E)-preference. Catalytic reduction of each isomer of 5 produced 5, 8a-disubstituted 1, 3, 3a, 8a-tetrahydro-2H-benzofuro[2, 3-b]pyrrol-2-ones (6) in moderate yields.
A Convenient One-Pot Synthesis of 4-Substituted 3,5-Bis(alkoxycarbonyl) -4,5-dihydroisoxazole 2-Oxides from Aldehydes and Nitroacetic Esters in a Solid-Liquid Reaction System and Subsequent Deoxygenation
4-Substituted 3,5-bis(alkoxycarbonyl)-4,5-dihydroisoxazole 2-oxides are obtained from nitroacetic esters and imines which are prepared from aldehydes and isopropylamine in the presence of molecular sieves. Reduction of the N-oxides with trimethyl phosphite in dioxane gives the corresponding 4,5-dihydroisoxazoles in good yields.
Highly diastereoselective condensation of α-nitro-esters with aldehydes catalyzed by zinc complexes of amino acids
作者:A. Chatterjee、S.C. Jha、N.N. Joshi
DOI:10.1016/s0040-4039(02)01047-x
日期:2002.7
Zinc complexes of amino acids efficiently catalyze the condensation between α-nitro-esters and a variety of aldehydes. An unusual domino reaction sequence leads to the diastereoselective formation of substituted isoxazoline N-oxides in high yields.