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。
Highly Enantioselective Cyanoformylation of Aldehydes Catalyzed by a Mononuclear Salen-Ti(OiPr)4 Complex Produced In Situ
An efficient enantioselectivecyanoformylation of aldehydes with ethylcyanoformate, catalyzed by a salen-Ti(OiPr)4 complex generated in situ, has been developed. Studies of nonlinear effects indicated that the mononuclear salen-titanium complex, and not a heterochiral complex, played a key role in the stereodiscriminating step of the reaction. During the preparation of the catalyst, the addition of
Asymmetric Cyanation of Aldehydes, Ketones, Aldimines, and Ketimines Catalyzed by a Versatile Catalyst Generated from Cinchona Alkaloid, Achiral Substituted 2,2′-Biphenol and Tetraisopropyl Titanate
Full investigation of cyanation of aldehydes, ketones, aldimines and ketimines with trimethylsilyl cyanide (TMSCN) or ethyl cyanoformate (CNCOOEt) as the cyanide source has been accomplished by employing an in situ generated catalyst from cinchona alkaloid, tetraisopropyl titanate [Ti(OiPr)4] and an achiral modified biphenol. With TMSCN as the cyanide source, good to excellent results have been achieved
Synthetic and mechanistic studies on asymmetric cyanohydrin synthesis using a titanium(salen) bimetallic catalyst
作者:Yuri N. Belokon'、A. John Blacker、Paola Carta、Lisa A. Clutterbuck、Michael North
DOI:10.1016/j.tet.2004.07.098
日期:2004.11
A bimetallic titanium(salen) complex 1 was found to catalyse the asymmetric addition of ethyl cyanoformate to aldehydes. Best results were obtained using 5 mol% of the catalyst at −40 °C and under these conditions, both aromatic and aliphaticaldehydes were converted into cyanohydrin carbonates with up to 99% enantiomeric excess. The same catalyst could also be used to catalyse the asymmetric addition