功能化烯胺的合成(II):一锅法由缺电子烯烃合成相应的α-脱氢氨

Synthesis of Functionalized Enamines(II): One-Pot Method for the Synthesis of α-Dehydroamino from Electron-Deficient Olefins

建立了一锅法由缺电子烯烃合成相应α-脱氢氨的新方法.缺电子烯烃(包括α,β-不饱和酯和α,β-不饱和酮)与对甲基苯磺酰胺/NBS在二氯甲烷中,室温下铝粉催化,首先发生双键上的氨溴加成反应,得到邻位氨基溴化合物.氨溴加成产物不经分离,再在二氯甲烷/DMF(V∶V=1∶1)的混合溶剂中,在碳酸钾/硫脲的催化下,各种邻位氨基溴的酯和邻位氨基溴的酮均能被顺利地转化成相应的α-脱氢氨.共考察了27种缺电子烯烃的反应行为,最高收率可达97%,证明该方法具有广泛的适应性.对所有产物的结构分析证明(1H NMR),所得到的脱氢氨,其氨基均处在羰基的α-位,证明该反应具有区域专一性.

An easy and efficient one-pot method for the synthesis of the functionalized enamines from the electron-deficient olefins has been developed. The electron-deficient olefins（including α,β-unsaturated esters and ketones） reacted with p-toluenesulfonamide（TsNH2）/N-bromosuccinimide（NBS） in CH2Cl2 catalyzed by Al powder（5 mol%） at room temperature to generate corresponding α,β-vicinal bromoamines in the first step. Following those, the mixture products without separation can be direct smoothly converted into corresponding α-dehydroamino derivatives catalyzed by thiourea（50 mol%） and K2CO3（50 mol%） in mixture solvents [V（CH2Cl2） ∶V（DMF）=1∶1] at room temperature in good to excellent yields（up to 97%）. 27 structurally different electron-deficient substrates were investigated. The results indicate that the protocol has applicability in a large scope of electron-deficient olefins. Based on the analysis of the all products in structure with 1H NMR, it was revealed that the amino groups were linked at the α-position of carbonyl to the dehydroamino derivatives. This result indicates that the one-pot method has full regiospecificity.