Isoxazoles and Isoxazolines by 1,3-Dipolar Cycloaddition: Base-Catalysed Condensation of Primary Nitro Compounds with Dipolarophiles
作者:Fabrizio Machetti、Luca Cecchi、Elena Trogu、Francesco De Sarlo
DOI:10.1002/ejoc.200700276
日期:2007.9
1,4-Diazabicyclo[2.2.2]octane (DABCO) or other suitable N-bases cause primaryactivatednitrocompounds to condense with alkenes to yield isoxazolines or with alkynes to give isoxazoles. As the molar ratio of the base with respect to the dipolarophile decreased, the reaction became slower, but the nitrocompound became more resistant to hydrolytic cleavage. The best results were achieved with a molar
1,4-二氮杂双环 [2.2.2] 辛烷 (DABCO) 或其他合适的 N-碱导致初级活化硝基化合物与烯烃缩合生成异恶唑啉或与炔烃缩合生成异恶唑。随着碱与偶极体的摩尔比降低,反应变慢,但硝基化合物对水解裂解的抵抗力更强。碱的摩尔比在 0.05-0.1 范围内时获得最佳结果。反应在氯仿中于 60 °C 下进行;对于硝基乙酸乙酯和苯基硝基甲烷,可以使用 80 °C 的乙醇获得更好的结果和更短的反应时间。建议采用催化循环:
Synthesis of β-Substituted α-Amino Acids via Lewis Acid Promoted Radical Conjugate Additions to α,β-Unsaturated α-Nitro Esters and Amides
作者:G. S. C. Srikanth、Steven L. Castle
DOI:10.1021/ol036461h
日期:2004.2.1
[reaction: see text] Beta-substituted alpha,beta-unsaturated alpha-nitro esters and amides undergo radical conjugate additions when treated with an appropriate Lewis acid. Deuterium studies revealed that the acidic alpha-stereocenter of the alpha-nitro ester products does not racemize under strictly controlled workup conditions. The alpha-nitro amides did racemize significantly during chromatography
MANJUNATHA, SULUR G.;REDDY, K. VENODHAR;RAJAPPA, SRINIVASACHARI, TETRAHEDRON LETT., 31,(1990) N, C. 1327-1330
作者:MANJUNATHA, SULUR G.、REDDY, K. VENODHAR、RAJAPPA, SRINIVASACHARI
DOI:——
日期:——
Nitroketene-s,n-acetals as precursors for nitroacetamides and the elusive nitrothioacetahides
作者:Sulur G. Manjunatha、K. Venodhar Reddy、Srinivasachari Rajappa
DOI:10.1016/s0040-4039(00)88798-5
日期:1990.1
1-Amino-1-methylthio-2-nitroethenes (2) can be converted in high yields to the Nitroacetamides (3) by Hg2+ catalysed hydrolysis and to the Nitrothioacetamides (4) by Na2S in ethanol-acetic acid.
Synthesis of β-Substituted α-Amino Acids via Lewis Acid Promoted Enantioselective Radical Conjugate Additions
作者:Liwen He、G. S. C. Srikanth、Steven L. Castle
DOI:10.1021/jo051334f
日期:2005.9.1
Lewisacid promoted radicalconjugateadditions to β-substituted α,β-unsaturated α-nitro esters and amides were investigated. With achiral Lewisacids, there was competition between the desired radicalconjugateaddition and undesired alkene reduction mediated by Bu3SnH. Zinc Lewisacids provided the greatest amounts of addition products with both substrate classes. Studies with Bu3SnD indicated that