用^1HNMR芳烃质子鉴定α—卤代桂皮酰胺类化合物的构型

桂皮酰胺类化合物的Z或E—构型,影响其对中枢神经的药理作用（兴奋或抑制）,根据NMR测定结果,该类烯氢未取代的化合物,可以用两个烯氢的偶合常数大小来鉴定其构型（JE】JZ）;α—卤代的桂皮酰胺,可根据β—烯氢的化学位移(δH（z）】δH（E）,差别大于1 ppm)和NH的化学位移(δH（z）】δH（E）)来区分.但对α—卤代的桂皮酰哌啶类化合物,其哌啶环的氮上无氢,两种构型的β—烯氢的化学位移的差别也不大,可以利用（?）C=O与β—烯氢的偶合常数3JCH来区别.但3JCH不易测定,干扰因素也多.有些化合物可根据N上取代基的大小,导致（?）C（?）键和芳环自由转动程度不同及优势构象各异、面角改变等来鉴定构型（Z或E）.综合和比较这些化合物的1H谱发现α—卤代桂皮酰胺类化合物,不论酰胺氮上带有何种取代基,苯环上取代基的种类与数目,芳烃质子的化学位移与峰形,Z型和E型有显著的不同,特别是α—位为较大的溴原子取代时,这种差别更明显,可用于鉴定这些化合物的构型.

Conjugate addition‐enantioselective protonation to forge tertiary stereocentresαto azaarenes via cooperative hydrogen atom transfer and chiral hydrogen‐bonding catalysis

Cooperative hydrogen atom transfer and chiral hydrogen‐bonding catalysis as a new platform for the asymmetric synthesis of azaarene derivatives is reported.By using a tetrabutylammonium decatungstate as the photocatalyst and a chiral phosphoric acid as the hydrogen‐bonding catalyst,transformations of a variety of commercially available hydrocarbons and silanes with diverseα‐branched 2‐vinylazaarenes could efficiently experience a tandem radical conjugate addition and enantioselective protonation process,providing a convenient and fully atom economical approach to access a range of valuable enantioenrichedα‐tertiary azaarenes in high yields with good to excellent enantioselectivities(up to 93%ee).Through the direct use of tert‐butyl methylcarbamate as the feedstock,this method enables a highly practical and concise synthesis of the enantiomerically pure medicinal molecule pheniramine(Avil).