(S)-2-fluoronitriles (S)-4 are obtained in good chemical and high optical yields from (R)-cyanohydrins (R)-2 or (R)-cyanohydrin trimethylsilylethers (R)-3 by fluorination with DAST or by nucleophilic substitution of alpha-sulfonyloxynitriles (R)-6, 7 with fluoride on polymeric supports (Amberlyst A-26 F-) under inversion of configuration of the starting cyanohydrins.
Synthesis of the bifunctional BINOL ligands and their applications in the asymmetric additions to carbonyl compounds
作者:Ying-Chuan Qin、Lan Liu、Michal Sabat、Lin Pu
DOI:10.1016/j.tet.2006.06.049
日期:2006.10
the diphenylzinc addition which often require the addition of a significant amount of diethylzinc with cooling (or heating) the reaction mixture in order to achieve high enantioselectivity, using (S)-8 needs no additive and gives excellent results at room temperature. (S)-8 in combination with diethylzinc and Ti(OiPr)4 can catalyze the highly enantioselective phenylacetylene addition to aromatic aldehydes
分别从BINOL和H 8 BINOL与吗啉代甲醇的反应中开发了双功能BINOL和H 8 BINOL配体(S)-6和(S)-8的高效一步合成方法。这些化合物的X射线分析表明它们在结构上有相似之处和不同之处。双功能H 8 BINOL(S)-8已发现对二苯基锌与许多脂族和芳族醛的反应具有很高的对映选择性,尤其是对于线性脂族醛而言,对映选择性最强的催化剂。与开发用于添加二苯锌的其他催化剂不同,该催化剂通常需要在冷却(或加热)的同时添加大量的二乙基锌以实现高对映选择性,使用(S)-8无需添加剂,在室温下可获得优异的结果温度。(S)-8与二乙基锌和Ti(O i Pr)4结合可以催化高度对映选择性的苯乙炔加成芳族醛。尽管对映选择性还不是很高,但它在室温下还可以促进苯乙炔向苯乙酮的添加。在不使用Ti(O i Pr)4和路易斯碱添加剂的情况下,(S)-8与二乙基锌结合可以催化丙酸甲酯与醛的反应,形成高官能度
A High‐Throughput Screening Method for the Directed Evolution of Hydroxynitrile Lyase towards Cyanohydrin Synthesis
Hydroxynitrile lyases (HNLs) catalyze the enantioselective cleavage/formation of cyanohydrins. However, current methods for determining hydrocyanation are not suitable for mass screening of mutants for protein engineering of these biocatalysts. We demonstrate herein a chromogenic high‐throughput screening method for cyanohydrinsynthesis that is validated by either substrate profiling or the directed evolution
Asymmetric Amino Acid Synthesis: Mitsunobu Reaction on Chiral Cyanohydrins
作者:Carl Decicco、Paul Grover
DOI:10.1055/s-1997-6139
日期:1997.6
BOC(SES)NH was reacted with chiral cyanohydrins using the Mitsunobu reaction to give good yields of protected α-aminonitriles, which were converted to chiral amino and imino acids.
Asymmetric Synthesis of a New Salen Type-titanium Complex as the Catalyst for Asymmetric Trimethylsilylcyanation of Aldehydes
作者:Zheng-Chang Lin、Chinpiao Chen
DOI:10.1002/jccs.201000101
日期:2010.8
This work describes the asymmetric synthesis of a new salen‐type ligand via a Diels‐Alder reaction and Curtius rearrangement. The ligand with a norbornane skeleton was used in the trimethylsilylcyanation of aldehydes, but the enantioselectivity was 55%ee. The norborane skeleton was cleaved to destroy this rigidity, and the eanatioselectivity was thereby increased to 85%ee.
The vanadium(V)(salalen) complex prepared in situ from the corresponding vanadium(IV) complex 4 under aerobic conditions was found to be an excellent catalyst for asymmetric transcyanation of aliph...