Catalytic Asymmetric Cyano-Ethoxycarbonylation Reaction of Aldehydes Using a Novel <i>C</i><sub>2</sub>-Symmetric Chiral <i>N</i>,<i>N</i>′-Dioxide Titanium Complex
作者:Xiaoming Feng、Qinghan Li、Lu Chang、Xiaohua Liu
DOI:10.1055/s-2006-947322
日期:2006.7
The asymmetric addition of ethyl cyanoformate to a range of aldehydes was efficiently catalyzed by a easily prepared C 2 -symmetric chiral N,N'-dioxide-Ti(IV) complex in high yields with up to 90% ee under mild conditions. A linear effect between the enantiopurity of the ligand and the enantiopurity of the product was observed.
氰基甲酸乙酯与一系列醛的不对称加成被一种易于制备的 C 2 -对称手性 N,N'-二氧化钛-Ti(IV) 配合物有效催化,在温和条件下的收率高达 90%。观察到配体的对映纯度和产物的对映纯度之间存在线性效应。
Asymmetric Cyanoethoxycarbonylation of Aldehydes Catalyzed by Heterobimetallic Aluminum Lithium Bis(binaphthoxide) and Cinchonine
catalytic asymmetriccyanoethoxycarbonylation of aldehydes was achieved by 10 mol % cinchonine with 10 mol % heterometallic (S)-aluminum lithiumbis(binaphthoxide), which gave the cyanohydrins ethyl carbonates in excellent isolated yields (up to 99 %) with moderate to high enantioselectivities (up to 95 % ee) under mild conditions (at −20 °C). Especially, the solid aluminumlithiumbis(binaphthoxide) free
Asymmetric cyano-ethoxycarbonylation of aldehydes catalyzed by self-assembled titanium catalyst
作者:Shaohua Gou、Xiaohua Liu、Xin Zhou、Xiaoming Feng
DOI:10.1016/j.tet.2007.05.060
日期:2007.8
aromatic aldehydes, aliphatic aldehydes, and α,β-unsaturated aldehydes were found to be suitable substrates in the presence of the self-assembled titanium catalyst (5 mol % 1h, 5 mol % 2b, and 5 mol % Ti(OiPr)4). The desired cyanohydrin ethyl carbonates were afforded with high isolated yields (up to 95%) and moderate to good enantioselectivities (up to 92% ee) under mild conditions (at −15 °C). A possible
已经开发了一种基于钛配合物的新型自组装催化剂,用于醛的有效对映选择性氰基-乙氧基羰基化。自组装催化剂很容易由(R)-3,3'-双((甲基((S)-1-苯基乙基)氨基)甲基)-1,1'-联萘-2,2'-二醇(1h),N -((1S,2R)-2-羟基-1,2-二苯乙基)乙酰胺(2b)和钛酸四异丙酯(Ti(O i Pr)4)。发现在自组装钛催化剂(5 mol%1h,5 mol%2b,和5mol%的Ti(O i Pr)4)。在温和的条件下(-15℃)以较高的分离产率(最高95%)和中等至良好的对映选择性(最高92%ee)提供了所需的氰醇乙酯碳酸酯。提出了基于实验观察的可能的催化循环。
Efficient Two-Step Conversion of α,β-Unsaturated Aldehydes to Optically Active γ-Oxy-α,β-unsaturated Nitriles and Its Application to the Total Synthesis of (+)-Patulolide C
[reaction: see text] An efficient two-step conversion of alpha,beta-unsaturated aldehydes into opticallyactive gamma-oxy-alpha,beta-unsaturated nitriles is described. First, catalytic asymmetric cyanation-ethoxycarbonylation using (S)-YLi(3)tris(binaphthoxide) (YLB) afforded chiral allylic cyanohydrin carbonate. Second, a [3,3]-sigmatropic rearrangement proceeded without racemization under thermal
Dual activation by a chiral Lewis acid and an achiral or chiral Lewis base enabled cyanation of both aromatic and aliphatic aldehydes with acetyl cyanide and ethyl cyanoformate to provide direct access to O-acetylated and O-alkoxycarbonylated cyanohydrins, respectively, under mild conditions. With a combination of a Ti-salen catalyst and Et3N, benzaldehyde was converted to the O-acetylated cyanohydrin