Enantioselective O-acetylcyanation/cyanoformylation of aldehydes using catalysts with built-in crown ether-like motif in chiral macrocyclic V(V) salen complexes
作者:Noor-ul H. Khan、Arghya Sadhukhan、Nabin C. Maity、Rukhsana I. Kureshy、Sayed H.R. Abdi、S. Saravanan、Hari C. Bajaj
DOI:10.1016/j.tet.2011.07.005
日期:2011.9
bis-aldehydes 2 and 3 were synthesized and used as efficientcatalysts in asymmetric cyanation reactions. The V(V) catalysts demonstrated excellent performance (product yields and ees up to 99%) with potassium cyanide (KCN) and sodium cyanide (NaCN). The catalytic system also performed very well with a safer source of cyanide-ethyl cyanoformate to give cyanohydrin carbonates in excellent yield and ee (up
通过1 R,2 R -(-)二氨基环己烷/(1 R,2 R)-(+)-1,2-二苯基乙二胺与双的反应获得的大环配体衍生的手性大环V(V)salen络合物1a – f合成了2-醛2和3-醛,并将其用作不对称氰化反应的有效催化剂。V(V)催化剂与氰化钾(KCN)和氰化钠(NaCN)一起表现出出色的性能(产品收率和ee高达99%)。使用更安全的氰化物-氰基甲酸乙酯源,该催化体系的性能也非常好,从而以优异的收率和ee(高达97%)得到氰醇碳酸盐。V(V)大环Salen络合物1b保持其在多克水平的性能,并方便地回收了许多次。
Dual Lewis Acid−Lewis Base Activation in Enantioselective Cyanation of Aldehydes Using Acetyl Cyanide and Cyanoformate as Cyanide Sources
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
Enantioselective Synthesis of Aliphatic Cyanohydrin Acetates
作者:Ulf Hanefeld、Lars Veum
DOI:10.1055/s-2005-872671
日期:——
When the standard conditions for the enantioselective synthesis of cyanohydrin acetates via dynamic kinetic resolution are applied to aliphatic substrates, only a kinetic resolution is observed. However, by exchanging the base (Amberlite) against NaCN, quantitative conversions and good enantioselectivities are obtained.
One-Pot Synthesis of Optically Active Cyanohydrin Acetates from Aldehydes via Quinidine-Catalyzed Transhydrocyanation Coupled with Lipase-Catalyzed Kinetic Resolution in Organic Solvent
作者:Minoru Inagaki、Akihiko Hatanaka、Mitsuo Mimura、Jun Hiratake、Takaaki Nishioka、Jun’ichi Oda
DOI:10.1246/bcsj.65.111
日期:1992.1
transhydrocyanation allows for in situ racemization of the unreacted cyanohydrins and concurrent kineticresolution by lipase enabled the preparation of (S)-3b–d with 40–82% e.e. in more than 50% yield. Polymer-supported cinchona alkaloid was also used as a catalyst for this one-pot reaction and showed the comparable chemical and optical yield to that for the soluble monomeric alkaloid. The insoluble polymer and lipase
开发了一种新的一锅合成方法来制备旋光氰醇乙酸酯。通过奎尼丁催化的氢氰化反应从醛和丙酮氰醇中生成外消旋氰醇,然后使用乙酸异丙烯酯作为酰化剂,通过脂肪酶以立体选择性方式将所得氰醇 2a-j 乙酰化。多种醛 1a-j 成功地转化为相应的氰醇乙酸酯 3a-j,其 ee 为 47-95%,而没有分离不稳定的氰醇 2。此外,碱催化转移氢氰化的可逆性质允许未反应的氰醇原位外消旋化脂肪酶同时进行动力学拆分使 (S)-3b-d 能够以 50% 以上的产率制备 40-82% ee 的 (S)-3b-d。聚合物负载的金鸡纳生物碱也被用作这种一锅反应的催化剂,并显示出与可溶性单体生物碱相当的化学和光学产率。不溶性聚合物和脂肪酶...
Minor Enantiomer Recycling: Metal Catalyst, Organocatalyst and Biocatalyst Working in Concert
A minorenantiomerrecycling one‐pot procedure employing two reinforcing chiral catalysts has been developed. Continuous regeneration of the achiral starting material is effected via selective enzyme‐catalyzed hydrolysis of the minor product enantiomer from Lewis acid–Lewis base catalyzed addition of acyl cyanides to prochiral aldehydes in a two‐phase solvent system. The process provides O‐acylated
已开发出一种使用两种增强手性催化剂的较小对映体回收一锅法。非手性原料的连续再生是通过路易斯酸-刘易斯碱在两相溶剂体系中将酰基氰化物加成到手性醛中的次要产物对映异构体的选择性酶催化水解来实现的。该方法提供的O-酰化氰醇接近完美的对映选择性,高于直接法获得的对映选择性,并且收率很高。(S,S)-salen Ti Lewis酸和南极假丝酵母脂肪酶B的组合可提供具有R绝对构型的产物,而相反的对映异构体可从(R,R)-salen Ti复合物和皱纹念珠菌脂肪酶。