Rhodium catalyzed hydroformylation of olefins

DFT and CCSD(T) methods were used to examine 61 different rhodium catalysts for the hydroformylation of ethylene. The carbon monoxide (CO) stretching frequency was a key electronic parameter to understand the π-accepting nature of the ligand. Normally, π-accepting ligands lead to increased CO stretching frequencies and a reduction in CO dissociation energy. There was no relationship between CO dissociation energy and CO stretching frequency. However, a clear relationship exists between the ethylene insertion barrier (from the rhodium dicarbonyl hydride resting state) and the CO stretching frequency as stronger π-accepting ligands systematically led to a reduction in the barrier. Due to the multistep nature of the rate-limiting step, the overall barrier can be divided into the CO/ethylene equilibrium and an intrinsic ethylene insertion barrier and both are systematically reduced as the π-accepting nature of the ligand is increased. A comparison of the carbonylation transition state (TS) to the ethylene insertion TS allowed us to understand reversibility of olefin insertion. While the ethylene insertion TS systematically decreases with increasing CO stretching frequency, the carbonylation TS is relatively flat. The lines cross at 2156 cm⁻¹ implying a change in the rate-limiting step in this region given a standard set of process conditions. © 2018 Wiley Periodicals, Inc.     

Highly enantioselective 1,4-conjugate addition of dialkylzinc to α,β-unsaturated lactone catalyzed by diphosphite-copper complexes

The 1,4-addition of diethylzinc and dimethylzinc to 5,6-hydro-2H-pyran-2-one using new chiral diphosphite-copper catalysts gave products in up to 98% ee.     

Michael addition of indoles to electron deficient olefins in water catalysed by potassium bisulfate

The Michael addition of indoles to various electron deficient olefins was performed in water using potassium hydrogen sulphate as catalyst at room temperature.     

Enantioselective copper catalysed 1,4-conjugate addition reactions using chiral N-heterocyclic carbenes

The preparation of a variety of chiral N-heterocyclic carbene (NHC) precursors is described. The relative merits of imidazolinium salts and silver carbenes as NHC precursors are discussed with respect to their synthesis, stability and performance in the copper catalysed conjugate addition of dialkyl zinc reagents to a variety of Michael acceptors. Enantioselectivities of up to 93% were achieved using as little as 4% of chiral ligand.     

Addition of heterocycles to electron deficient olefins and alkynes catalyzed by gold(III)

A gold(III)-catalyzed hydroarylation of different olefins is reported here. AuCl₃ works as an excellent catalyst to mediate reactions between various heterocycles and electron deficient olefins and alkynes under mild conditions. This gold(III)-based method tolerates different functional groups such as aldehyde, carboxylic acid, nitrile, and is highly efficient. We have shown that some of these reactions complete in minutes at room temperature.     

The first examples of rhodium-catalyzed 1,4-conjugate addition reactions of arylboronic acids with ethenesulfonamides

An unprecedented rhodium-catalyzed 1,4-conjugate addition of arylboronic acids with ethenesulfonamides resulting in the corresponding 2-arylethanesulfonamides is described. The amino substituent, the applied arylboronic acid, the type of Rh-catalyst, and the experimental conditions all affected the reaction outcome.     

Nonlinear effects in the enantioselective 1,4-conjugate addition of diethylzinc to chalcone

A clear positive nonlinear effect of the enantiopurity of ligand 1 on the product ee was observed in the enantioselective 1,4-conjugate addition of Et₂Zn to chalcone. The experimental data of nonlinear effect meet Kagan's ML₂ model.     

Inositols as chiral templates: 1,4-conjugate addition to tethered cinnamic esters

The 1,4-addition of thio nucleophiles to chiro-inositols containing a cinnamyl Michael acceptor proceeded with excellent diastereochemical induction and good yields. Cleavage of the inositol auxiliary provides beta-thio hydrocinnamic acids in >99% ee's.     

Dodecacarbonyltriruthenium catalyzed one-to-one addition of N-substituted formamide to olefins

Dodecacarbonyltriruthenium (Ru₃(CO)₁₂) showed high catalytic activity for the first one-to-one addition of N-substituted formamides to both terminal and internal olefins at 180-200°C under a carbon monoxide pressure of 20 kg cm⁻². The addition of N-metylformamide to cyclopentene afforded N-methylcyclopentanecarboxamide in 90% yield.     

An expeditious FeCl3-catalyzed cascade 1,4-conjugate addition/annulation/1,5-H shift sequence for modular access of all-pyrano-moiety-substituted chromenes

ortho-Alkynyl quinone methides are well-known four-atom synthons for direct [4 + n] cycloaddition in constructing useful oxa-heterocyclic compounds owing to their high reactivity as well as the thermodynamically favored aromatization nature of this process. Herein we report an operationally simple and eco-friendly protocol for the modular and regioselective access of (E)-4-(vinyl or aryl or alkynyl)iminochromenes from propargylamines and S-methylated β-ketothioamides in the presence of FeCl₃, and particularly under undried acetonitrile and air atmosphere conditions. This method exhibits a broad substrate scope and displays nice functional group compatibility, thus providing an efficient access of 3,4-disubstituted iminochromenes.

An operationally simple protocol is described for the facile, modular and regioselective access of all-pyrano-moiety-substituted iminochromenes, particularly under undried acetonitrile and air atmosphere.     

Advances on asymmetric organocatalytic 1,4-conjugate addition reactions in aqueous and semi-aqueous media

Asymmetric Michael addition reactions or 1,4-conjugate addition reactions are considered to be the fundamental C–C bond-forming reaction for the construction of chiral β-nitro, β-carbonyl and several other important structural motifs in organic synthesis. After the development of many chiral metal complexes as catalysts, a tremendous growth in the design and applications of variety of new chiral organocatalysts for asymmetric 1,4-conjugate addition reactions has been witnessed over the last two decades. Initially, asymmetric organocatalysis has been performed in organic solvents, but gradually performing the same catalysis in aqueous and semi-aqueous media became a necessity due to environmental aspects as well as to achieve better reactivity and selectivity. The structural and functional diversity of the chiral organocatalysts derived from natural and synthetic sources utilized differently the water either as the sole solvent, co-solvent or additive for optimising their best performances. In the present review, we discuss a detailed and comprehensive report on the advancement in the field of asymmetric organocatalytic 1,4-conjugate addition reactions in aqueous and semi-aqueous media.     

"One-pot" tandem C-H borylation/1,4-conjugate addition/reduction sequence

A microwave-assisted, one-pot, iridium-catalyzed aromatic C-H borylation/rhodium-catalyzed 1,4-conjugate addition sequence provides a highly robust protocol suitable for high-throughput array synthesis. Selective formation of either β-aryl-substituted ketones or the corresponding alcohols can be achieved in good overall yields by simple variation of the reaction conditions.     

The ortho effect: copper-catalyzed highly enantioselective 1,4-conjugate addition of diethylzinc to chalcones

The copper-catalyzed enantioselective 1,4-conjugate addition of diethylzinc to chalcones was investigated in the presence of a catalytic amount of N,P-ferrocenyl ligands with central and planar chirality under mild conditions (0 °C→rt). It was found that chalcones with ortho-substituents (from ortho-substituted benzaldehydes and acetophenone/substituted acetophenones) led to a dramatic improvement in the enantioselectivities. The (R)- and (S)-antipodes of the addition reaction were obtained with up to 92% ee after this transformation.     

新型P,N配体及基1,4-共轭加成反应

以2-萘酚为起始原料,经过氧化偶联,消旋体的拆分得到手性骨架2-氨基-2'-羟基-1,1'-联萘(NOBIN),并以S-NOBIN为原料,经过六步反应合成了两个新型配体S-(+)-2-(2-吡啶酰胺基)-2'-二苯基膦基-1,1'-联萘(1a)和S-(+)-2-(6-甲基-2-吡啶酰胺基)-2'-二苯基膦基-1,1'-联萘(1b)。并进行了铜配合物催化的二乙基锌对2-环己烯酮的1,4-共轭加成反应的研究。反应产物3-乙基环己酮(13)的e.e.值高达92%。     

(R)-4-menthenone in reactions of 1,4-conjugate and 1,3-dipolar addition

(R)-4-Menthenone compared with common cyclic enones exhibits considerably lower reactivity in 1,4-conjugate addition of organometallic reagents, is inert in Michael reactions and pyrazoline formation evidently due both to the distorted polarization in the enone system and to steric hindrances from the α-isopropyl group in the cyclohexene ring.     

The cuprous chloride catalyzed addition of halogen compounds to olefins under photo-irradiation

The addition of organic halogen compounds to olefins in the presence of cuprous chloride under U.V. irradiation gave 1:1 adducts.     

Catalytic direct 1,4-conjugate addition of aldehydes to vinylketones on secondary-amines immobilised in FSM-16 silica

Direct 1,4-conjugate addition of naked aldehydes to vinylketones is catalysed effectively by N-methyl-3-aminopropylated FSM-16 mesoporous silica, which can be regarded as a novel heterogeneous catalysis for a practical C-C bond formation reaction.     

Ruthenium catalyzed addition reaction of carboxylic acid across olefins without beta-hydride elimination

The cationic ruthenium catalyst (Cp*RuCl2)2/AgOTf/Ligand promotes the addition reaction of carboxylic acids across olefins without beta-hydride elimination.     

New bis(1-ferrocenylethyl)amine-derived monodentate phosphoramidite ligands for highly enantioselective copper-catalyzed 1,4-conjugate addition

A new family of chiral bis(1-ferrocenylethyl)amine-derived monodentate phosphoramidite ligands has been prepared and successfully applied in the Cu-catalyzed asymmetric 1,4-conjugate addition of diethylzinc to a variety of α,β-unsaturated compounds, in which up to 99% ee was obtained for nitroalkenes at ?78 °C and >98% ee for cyclohexenone at ?30 °C, comparable to or higher than those obtained with the most efficient monophosphoramidite ligands reported so far.