Zn粉作为催化剂前体催化对甲苯磺酰胺/二溴海因与烯烃的区域选择性和立体选择性氨溴加成反应

Zn粉作为催化剂前体, 在反应中可被原位氧化成高效Zn(Ⅱ)-催化剂. 在该催化剂催化下, 以对甲苯磺酰胺和1,3-二溴-5,5-二甲基乙内酰脲(二溴海因)为氮源/卤素源, 二氯甲烷作溶剂, 建立了烯键上的高度区域选择和立体选择性氨溴加成反应新体系. 该方法在室温下可高产率地制得邻位氨基溴的加成产物, 最高收率可达99%. 实验结果表明, 当与双键直接相连的苯环对位有强给电子基团(CH₃O)时, 反应收率高, 并可得到唯一的氨溴加成产物(α-溴-β-氨基); 当与双键直接相连的苯环对位有强拉电子基团(NO₂)或弱拉电子基团(如Br和F)时, 该反应的产率相对较低, 但也能制得另一个唯一的氨溴加成产物异构体(α-氨基-β-溴型). 本文考察了20种不同结构底物的氨溴加成反应情况, 产物结构经过¹H NMR、¹³C NMR和元素分析确证, 并探讨了该反应的机理.

Regio- and Stereoselective Aminobromination of Olefins with p-Toluenesulfonamide and 1,3-Dibromo-5,5-dimethyl Hydantoin Catalyzed by a New Catalyst Produced In-situ from Zinc Powder

A new system for the high regio- and stereoselective aminobromination of olefins with p-toluenesulfonamide(TsNH2) and 1,3-dibromo-5,5-dimethyl hydantoin(DBDMH) as nitrogen/bromine sources catalyzed by a new catalyst which produced in-situ from Zn powder has been developed. This protocol offered vicinal haloamine products in high yield(up to 99%) at room temperature in CH2Cl2. The strong electron-donating group(such as OCH3) are connected on the 4-position of the benzene ring which attached directly to the carbon-carbon double bond of substrats, the reaction afforded the trans isomers(α-bromo-β-amino) as the sole product up to nearly quantitative yield. However, the strong electron-withdrawing group(NO2) or the poor electron-withdrawing group(Br and F) are linked on the 4-position of the benzene ring, the reaction afforded the another reversal isomers in regioselective(α-amino-β-bromo) as the sole product, but the slightly low yields were obtained. In this paper, a series of the aminobromination of olefins(20 samples) have been investigated. The result indicates that the method has widely applicability to the aminobromination of olefins. All the product structures were characterized by 1H NMR, 13C NMR and elemental analysis, and the possible reaction pathway was proposed.