Radical-nucleophilic substitution (SRN1) reactions. Part 7. Reactions of aliphatic α-substituted nitro compounds.
作者:Suleiman I. Al-Khalil、W. Russell Bowman、Katherine Gaitonde、Madeleine A. Marley (née Nagel)、Geoffrey D. Richardson
DOI:10.1039/b103350f
日期:——
α-Nitrothiocyanates R2C(SCN)NO2 have been prepared by oxidative addition of thiocyanate anion to nitronate anions and undergo SRN1 substitution reactions by loss of thiocyanate with nitronate anions, phenylsulfinate, azide and p-nitro- and p-chloro-benzenethiolates in dipolar aprotic solvents. 2-Nitro-2-thiocyanatopropane and other 2-substituted-2-nitropropanes [Me2C(X)NO2 with X = I, Br, Cl, NO2, PhSO2] react with thiolates by SRN1 reactions and/or redox reactions to give disulfides by a polar abstraction or chain SET (SET2) mechanisms. The products are dependent on the nucleophilicity of the thiolates, the polarisability of the α-substituent, the solvent and the presence of light catalysis, radical traps or strong electron acceptors. 2-Substituted-2-nitropropanes [Me2C(X)NO2 with X = N3,
NO2, CN, p-NO2âC6H4âNN] undergo SRN1 substitutions with thiolates by loss of nitrite. 2-Substituted-2-nitropropanes Me2C(X)NO2 and thiolates only yield disulfides in methanol due to solvation of the nitro groups.
α-亚硝基硫氰酸酯R2C(SCN)NO2通过硫氰酸根离子对亚硝酸根离子的氧化加成制备,并在非质子性偶极溶剂中通过失去硫氰酸盐与亚硝酸根离子、苯磺酸盐、叠氮化物以及对硝基和对氯苯硫醇盐发生SRN1取代反应。2-硝基-2-硫氰酸丙烷和其他2-取代-2-硝基丙烷[Me2C(X)NO2,其中X=I、Br、Cl、NO2、PhSO2]通过SRN1反应和/或氧化还原反应与硫醇盐反应,通过极性提取或链SET(SET2)机制生成二硫化物。产物取决于硫醇盐的亲核性、α-取代基的极化性、溶剂以及光催化、自由基捕获剂或强电子受体的存在。2-取代-2-硝基丙烷[Me2C(X)NO2,其中X=N3、NO2、CN、p-NO2-C6H4-NN]在与硫醇盐失去亚硝酸盐的情况下发生SRN1取代。2-取代-2-硝基丙烷Me2C(X)NO2和硫醇盐仅在甲醇中由于硝基团的溶剂化而产生二硫化物。