Rhodium/chiral diene-catalyzed asymmetric 1,4-addition of arylboronic acids to arylmethylene cyanoacetates

Asymmetric 1,4-addition of arylboronic acids to (E)-methyl 2-cyano-3-arylpropenoates proceeded in the presence of a rhodium catalyst (3 mol %) coordinated with a chiral diene ligand, (R,R)-Ph-bod*, to give high yields of the corresponding methyl 3,3-diaryl-2-cyanopropanoates with high enantioselectivity (up to 99% ee). This catalytic asymmetric transformation was applied to the asymmetric synthesis of (R)-tolterodine.     

Rh/chiral sulfinylphosphine catalyzed asymmetric 1,4-addition of arylboronic acids to chalcones

A general method to obtain enantioenriched 1,3,3-triarylpropan-1-ones bearing a diarylmethine stereocenter was developed using Rh/chiral sulfinylphosphine catalyzed 1,4-addition of arylboronic acids to chalcones. The catalysis progressed smoothly in the presence of 2 mol % catalyst formed in situ from [Rh(C₂H₄)₂Cl]₂ and chiral tert-butanesulfinylphosphine and gave the adducts with up to 99% yield and 98% ee.     

Rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to coumarins: asymmetric synthesis of (R)-tolterodine

[reaction: see text]. Rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to coumarins proceeded with high enantioselectivity in the presence of a rhodium catalyst (3 mol %) generated from Rh(acac)(C2H4)2 and (R)-Segphos to give the corresponding (R)-4-arylchroman-2-ones in over 99% ee. This asymmetric reaction was applied to the synthesis of (R)-tolterodine.     

The rhodium-catalysed 1,2-addition of arylboronic acids to aldehydes and ketones with sulfonated S-Phos

The rhodium-catalysed 1,2-addition of arylboronic acids to aryl aldehydes has been accomplished in high yield using sulfonated S-Phos, a water-soluble biaryl phosphine ligand which allows for catalyst recycling. The catalytic protocol has also been successful in the challenging arylation of ketones.     

Planar chiral imidazolium salts based on [2.2]paracyclophane in the asymmetric rhodium-catalyzed 1,2-addition of arylboronic acids to aldehydes

A series of planar chiral imidazolium salts derived from [2.2]paracyclophane have been synthesized and characterized. By using these imidazolium salts as carbene precursors, the Rh-catalyzed 1,2-addition of arylboronic acids to aldehydes proceeded readily with low catalyst loadings (0.03–0.3 mol %) and gave a variety of chiral diarylmethanols in excellent yields and moderate enantioselectivities.     

Rhodium-catalyzed 1,4-addition of arylboronic acids to alpha,beta-unsaturated carbonyl compounds: large accelerating effects of bases and ligands

The effects of ligands and bases in the rhodium(I)-catalyzed 1,4-addition of arylboronic acids to alpha,beta-unsaturated carbonyl compounds were reinvestigated to carry out the reaction under mild conditions. Rhodium(I) complexes possessing a 1,5-cyclooctadiene (cod) and a hydroxo ligand such as [RhOH(cod)](2) exhibited excellent catalyst activities compared to those of the corresponding rhodium-acac or -chloro complexes and their phosphine derivatives. The reaction was further accelerated in the presence of KOH, thus allowing the 1,4-addition even at 0 degrees C. A cationic rhodium(I)-(R)-binap complex, [Rh(R-binap)(nbd)]BF(4), catalyzed the reaction at 25-50 degrees C in the presence of Et(3)N with high enantioselectivities of up to 99% ee for alpha,beta-unsaturated ketones, 92% for aldehydes, 94% for esters, and 92% for amides.     

Rhodium-catalyzed enantioselective 1,4-additions of arylboronic acids to substituted enones

The rhodium-catalyzed enantioselective 1,4-addition of arylboronic acids to the bifunctional Michael acceptors 1–3 in the presence of phosphoramidites L2–L4 occurs regioselectively at the endocyclic C–C double bond and in up to 95% ee. The presence of KOH is required to increase the reactivity so that less boronic acid and lower reaction temperatures can be used. The corresponding addition to chiral enone 4 takes place with epimerization of the product to the thermodynamically more stable trans-isomer, which was obtained with up to 98% ee.     

Rhodium-catalyzed asymmetric hydroarylation of diphenylphosphinylallenes with arylboronic acids

Rhodium-catalyzed asymmetric hydroarylation of diphenylphosphinylallenes with arylboronic acids proceeded in high yields with high regio- and enantioselectivity to give chiral allylphosphine oxides of up to 98% ee. The structural determination of the key intermediate, a pi-allylrhodium complex, was successful to establish the catalytic cycle of the reaction.     

Rhodium-catalyzed asymmetric 1,6-addition of aryltitanates to enynones giving axially chiral allenes

[reaction: see text] The addition of aryltitanate reagents ArTi(OPr-i)4Li to 3-alkynyl-2-en-1-ones in the presence of chlorotrimethylsilane and a rhodium-(R)-segphos as a catalyst proceeded in a 1,6-fashion to give a high yield of axially chiral allenylalkenyl silyl enol ethers with up to 93% ee.     

Preparation of chiral 7,7′-disubstituted BINAPs for Rh-catalyzed 1,4-addition of arylboronic acids

A series of new 7,7′-disubstituted BINAPs were readily prepared starting with an asymmetric catalytic oxidative coupling. They were applied as ligands to rhodium catalyzed 1,4-addition of arylboronic acids to enones, resulting in enantioselectivities of up to 99% ee. The enantioselectivity was found to be dependent on the size of achiral substituents.     

Rhodium-catalyzed addition of arylboronic acids to alkynyl aza-heteroaromatic compounds in water

Alkynyl heteroaromatic compounds reacted with arylboronic acids to give addition products in the presence of a rhodium catalyst. The best results were obtained when a novel pyridine-substituted water-soluble phosphine ligand was used. The reactions proceed to give trisubstituted alkenes from various arylboronic acids and alkynyl heteroaromatic compounds with high regioselectivity. Only alkynes with a nitrogen atom in proximity to the triple bond were converted to the corresponding alkenes, as expected for a chelation-controlled addition.     

Palladium/phosphite-catalyzed 1,4-addition of arylboronic acids to acrylic acid derivatives

1,4-Addition of arylboronic acids to acrylic acid derivatives proceeds efficiently in the presence of a palladium catalyst system of Pd(OAc)2/(PhO)3P to produce the corresponding 3-arylpropionic acid derivatives. The use of the phosphite ligand is the key to conducting the addition smoothly with suppressing the competing Mizoroki-Heck-type oxidative coupling.     

Rhodium-catalyzed asymmetric conjugate addition of arylboronic acids to nitroalkenes using olefin-sulfoxide ligands

An efficient rhodium/olefin-sulfoxide catalyzed asymmetric conjugate addition of organoboronic acids to a variety of nitroalkenes has been developed, where 2-methoxy-1-naphthyl sulfinyl functionalized olefin ligands have shown to be highly effective and are applicable to a broad scope of aryl, alkyl, and heteroaryl nitroalkenes.     

Rhodium-catalyzed addition/ring-opening reaction of arylboronic acids with cyclobutanones

Cyclobutanones react with arylboronic acids in the presence of a catalytic amount of Rh(I) complex to afford butyrophenone derivatives through the addition of an arylrhodium(I) species to the carbonyl group, followed by ring-opening of the resulting rhodium(I) cyclobutanolate. [reaction: see text]     

Rhodium-catalyzed asymmetric coupling reaction of allylic ethers with arylboronic acids

An asymmetric allylic substitution of simple allylic ethers with arylboronic acids in the presence of a rhodium(I)/(R)-DTBM-SEGPHOS catalyst has been developed. The reactions proceeded smoothly at room temperature to give the corresponding branch products with excellent regioselectivities and good to excellent enantioselectivities.     

Rhodium-catalyzed addition of aryl boronic acids to 1,2-diketones and 1,2-ketoesters

The metal complex Rh(acac)(CO)₂ in the presence of dicyclohexylphenylphosphine provides a useful catalyst system for the addition of boronic acids to 1,2-diketones and 1,2-ketoesters. The best yields were obtained when the transformation was performed in DME/H₂O at 80 °C with 4 equiv of the boronic acid. The results discussed herein extend the scope of the addition of arylboronic acids to highly activated diketones and ketoesters. The products of the reaction are useful in the synthesis of natural products containing oxygenation next to esters or ketones.     

Rhodium-catalyzed arylative cyclization of alkynones induced by addition of arylboronic acids

Alkynones react with arylboronic acids in the presence of a rhodium(I) catalyst to afford four- and five-membered-ring cyclic alcohols equipped with a tetrasubstituted exocyclic olefin. The cyclic allylic alcohol skeleton is constructed by the carbon-carbon bond formation between the carbonyl group and an alkenylrhodium(I) intermediate formed by the regioselective addition of an arylrhodium(I) species across the carbon-carbon triple bond.