SN2-Selective allylic substitution of chiral γ-aryl substituted allylic picolinates with alkynylcopper reagents
摘要:
Substitution of gamma-aryl secondary allylic picolinates with alkynyl copper reagents was studied. The copper reagent, prepared from TMSC equivalent to CMgBr and CuBr center dot Me-25 in 2:1, was subjected to substitution of the picolinate derived from (E)-3-phenyl-1-methyl-2-propenyl alcohol at 0 degrees C for 1 h in THF to produce a mixture of alpha- and gamma-products and the alcohol in 67:20:13, while the reagent in 3 or 4:1 ratio gave the alpha-product with 90-91% selectivity. On the contrary, reaction in CH2Cl2-THF (6-8:1) at 0 degrees C for 1 h furnished the alpha-product with 99% regioselectivity. The effect of CH2Cl2 was also demonstrated with eight more examples. Furthermore, 99% inversion was determined by transformation to the literature compound and by chiral H PLC. (C) 2010 Elsevier Ltd. All rights reserved.
炔丙醇和胺是有机合成中的通用组成部分。我们展示了一种简单的酶级联反应,可以从容易获得的外消旋起始材料合成对映异构纯的炔丙醇和胺。在第一步中,来自Agrocybe aegerita的过氧化酶将外消旋炔丙醇转化为相应的酮,然后使用来自开菲尔乳杆菌的 ( R )-选择性醇脱氢酶或 ( S )-选择性醇脱氢酶将其转化为对映体纯醇来自布罗基热厌氧菌. 此外,使用来自土曲霉的( R )-选择性胺转氨酶或来自紫色色杆菌的( S )-选择性胺转氨酶,建立了将外消旋醇酶促Mitsunobu型转化为对映体富集的炔丙基胺。一锅两步级联反应以 70-99% 的产率产生了范围广泛的对映体富集的醇和胺产物。
Asymmetric catalysis with readily available, cheap, and non-toxic alkaline earth metal catalysts represents a sustainable alternative to conventional synthesis methodologies. In this context, we describe the development of a first MgII -catalyzed enantioselective hydroboration providing the products with excellent yields and enantioselectivities. NMR spectroscopy studies and DFT calculations provide
The oxidoreductases Lactobacillus brevis alcohol dehydrogenase (LBADH) and Candida parapsilosis carbonyl reductase (CPCR) are suitable catalysts for the reduction of ketones to afford enantiopure sec. alcohols. A broad variety of alkynones (1, 3, and 5) are accepted as substrates and the corresponding propargylic alcohols (2, 4, and 6) are obtained in good yield and excellent enantiomeric excess. By
A Boron–Oxygen Transborylation Strategy for a Catalytic Midland Reduction
作者:Kieran Nicholson、Joanne Dunne、Peter DaBell、Alexander Beaton Garcia、Andrew D. Bage、Jamie H. Docherty、Thomas A. Hunt、Thomas Langer、Stephen P. Thomas
DOI:10.1021/acscatal.0c05168
日期:2021.2.19
The enantioselective hydroboration of ketones is a textbook reaction requiring stoichiometric amounts of an enantioenriched borane, with the Midland reduction being a seminal example. Here, a turnover strategy for asymmetric catalysis, boron–oxygen transborylation, has been developed and used to transform the stoichiometric boranereagents of the Midland reduction into catalysts. This turnover strategy
naphthyl 1-propargyl ethers through para-Claisen rearrangement was described, and chirality transfer was observed. Moreover, the enantioselective dearomatization of C4-substituted substrates was realized by using a chiral N,N′-dioxide/CoII complex catalyst. The DFT calculations and experimental results support the ortho-Claisen rearrangement/Cope rearrangement sequence process.