stereodivergent Pd/Cu catalyst system has been developed for the unprecedented dynamickineticasymmetrictransformation (DyKAT) of racemic unsymmetrical 1,3-disubstituted allylic acetates with prochiral aldimine esters. A series of α,α-disubstituted α-amino acids bearing vicinal stereocenters were easily prepared with excellent enantioselectivities (up to >99% ee) and diastereoselectivities (up to >20:1 dr). By
A DYKAT die hard: A new class of chiral BiSO‐P ligands were effective for an unprecedented palladium‐catalyzed asymmetricallylicalkylation of indoles with the racemic title acetates through a dynamickineticasymmetrictransformation (DYKAT). The hydrogen bond formed between the sulfinyl group of the ligand and NH of indole plays an important role in the reaction.
Hydroxynitrilelyases (HNLs) catalyse the reversible cleavage of cyanohydrins to carbonyl compounds and HCN. The recent discovery of bacterial HNLs with a cupin fold gave rise to a new promising class of these enzymes. They are interesting candidates for the synthesis of cyanohydrins on an industrial scale owing to their high expression levels in Escherichia coli. The activity and enantioselectivity
Synthesis of (<i>S</i>)-Imperanene by Using Allylic Substitution
作者:Yuji Takashima、Yuichi Kobayashi
DOI:10.1021/jo900854p
日期:2009.8.21
Synthesis of (S)-imperanene (1) was studied by using copper-assisted allylic substitution of ArCH═CHCH(L)CH2Ar (L: leaving group) and (i-PrO)Me2SiCH2MgCl. Preliminary substitution between PhCH═CHCH(L)Me (L = AcO, PivO, MeOCO2, (2-Py)CO2) and Bu copper reagents derived from BuMgX (X = Br, Cl) and CuBr·Me2S or CuCl in 1:1−40:1 ratios suggested acetate 28 as the best substrate. To prepare 28, kinetic
通过使用铜辅助的ArCH = CHCH(L)CH 2 Ar(L:离去基团)和(i- PrO)Me 2 SiCH 2 MgCl的烯丙基取代研究了(S)-紫杉醇(1)的合成。PhCH═CHCH(L)Me(L = AcO,PivO,MeOCO 2,(2-Py)CO 2)和由BuMgX(X = Br,Cl)和CuBr·Me 2 S或CuCl衍生的Bu铜试剂之间的初步取代以1:1−40:1的比例建议乙酸盐28是最好的底物。为制备28,外消旋(E)-TMSCH═CHCH(OH)CH 2 Ar 2(Ar 2 =(通过使用与(-)-DIPT的不对称环氧化进行的对-TBSO)(m- MeO)C 6 H 3),得到相应的环氧醇和(S)-烯丙基醇。经色谱分离后,这些产物转化为(S,E)-Bu 3 SnCH = CHCH(OH)CH 2 Ar 2,经钯催化与Ar 2 -I偶联,然后乙酰化,得到28(95-98% ee)。用(i
Enantioselective Allylic Alkylation with 4-Alkyl-1,4-dihydro-pyridines Enabled by Photoredox/Palladium Cocatalysis
作者:Hong-Hao Zhang、Jia-Jia Zhao、Shouyun Yu
DOI:10.1021/jacs.8b10766
日期:2018.12.12
alkylation has been achieved enabled by the merger of photoredox and palladiumcatalysis. In this dual catalytic process, alkyl radicals generated from 4-alkyl-1,4-dihydropyridines act as the coupling partners of the π-allyl palladium complexes. The generality of this method has been illustrated through the reaction of a variety of allylesters with 4-alkyl-1,4-dihydropyridines. This mechanistically novel