温和的还原剂四甲基铵三乙酰氧基硼氢化物以高非对映选择性将无环 P-羟基酮还原为其相应的反二醇。α-烷基取代不会显着影响这些还原的立体选择性。在所有检查的情况下,都获得了良好到极好的非对映异构体均质二醇的产率。这些还原的机制涉及三乙酰氧基硼氢化物阴离子将乙酸盐与底物醇进行酸促进的配体交换。所得氢化物中间体,大概是烷氧基二乙酰氧基硼氢化物,还原近端 OH 0 OH OH 0 Me,NHB(OAc), Mew Me&OR - OR Me he
Ag–Cu nanoparticles as efficient catalysts for transesterification of β-keto esters under acid/base-free conditions
作者:Hongmei Yue、Hao Yu、Sheng Liu、Chunli Xu
DOI:10.1039/c6ra00467a
日期:——
Transesterification of β-ketoesters and alcohols are traditionally catalyzed by acid or basic catalysts. However, these traditional catalysts do not always meet the requirements of modern synthetic chemistry which need to be highlyefficient, selective, and environmentally friendly. In this work, Ag–Cu metal sites were first introduced as transesterification catalysts. The effect of the support, Ag : Cu
New analogues of nifedipine, in which the ortho-nitro phenyl group at position 4 has been replaced by 4(5)-chloro-5(4)-imidazolyl substituent and which are able to interact with the receptor by hydrogen binding were designed, synthesized, and evaluated as calciumchannelantagonists. The designed dihydropyridines were synthesized using the Hantzsch condensation and evaluated as calciumchannel antagonists
Synthesis and biological evaluation of some new 1,4-dihydropyridines containing different ester substitute and diethyl carbamoyl group as anti-tubercular agents
derivatives with lipophilic groups have significant anti-tubercular activity. In this study, we synthesized new derivatives of 1,4-dihydropyridines in which different alkyl and aryl esters and diethylcarbamoyl are substituted in C-3 and C-5 of the DHP ring. In addition nitroimidazole ring is substitutes at C-4 position. These asymmetric analogues were synthesized by a modified Hantzsh reaction using
assessed. The results for symmetrical esters showed that lengthening of the methylene chain in C3 and C5 estersubstituents increased activity. When increasing of the length is accompanied by increasing the hindrance, the activity decreased. In contrast to symmetrical derivatives, comparison of the activities of asymmetrical esters showed that increasing the length of the methylene chain was accompanied
‐(4)‐imidazolyl substituent, were synthesized and evaluated as calciumchannelantagonists using the high K+ contraction of guinea pig ileal longitudinal smooth muscle. The results for the symmetrical ester series showed that increasing the length of the chain in C3‐ and C5‐ester substituents increased the activity and the most active compound was the diphenylethyl ester derivative, so it was more
硝苯地平的一系列二烷基、二环烷基和二芳基酯类似物,其中 4 位的邻硝基苯基被 4-(5)-氯-2-乙基-5-(4)-咪唑基取代,使用豚鼠回肠纵向平滑肌的高 K + 收缩合成并评估钙通道拮抗剂。对称酯系列的结果表明,增加C3-和C5-酯取代基中链的长度会增加活性,活性最强的化合物是二苯乙酯衍生物,因此比参考药物硝苯地平更具活性。在不对称二酯系列中,当 R1 为甲基或乙基时,增加 R 取代基的亲油性,增加活性。最活跃的化合物是甲基/苯乙基和乙基/苯乙基酯衍生物,