Sakae Uemura

PD(OAC)2-CATALYZED OXIDATION OF ALCOHOLS TO ALDEHYDES AND KETONES BY MOLECULAR OXYGEN

A novel combination of Pd(OAc)2/pyridine/MS3A catalyzes the aerobic oxidation of various benzylic alcohols into corresponding aldehydes and ketones in good yield. Primary and secondary aliphatic alcohols also are smoothly oxidized to aldehydes and ketones, respectively, under the same conditions.

Palladium-catalyzed cross-coupling of aryl and alkenyl boronic acids with alkenes via oxidative addition of a carbonboron bond to palladium(O)

Abstract Arylboronic acids react with alkenes in acetic acid at 25°C in the presence of a catalytic amount of palladium(II) acetate together with sodium acetate to give the corresponding aryl-substituted alkenes in high yields. Alkenylboronic acids react with alkenes under similar conditions to give the corresponding conjugated dienes stereospecifically, but the product yields are lower, compared with those from arylboronic acids. Similar treatment of sodium tetraphenylborate (NaBPh 4 ) with alkenes also affords the corresponding phenylated alkenes in high yields together with biphenyl and benzene as side products. Oxidative addition of a carbonboron bond to palladium(O), formed in situ , to give an organopalladium(II) species is assumed to be the key step of these cross-coupling reactions.

Phosphine-nickel(II), -cobalt(II), -palladium(0) and -palladium(II) complexes as catalysts in cross-coupling reactions of aryl- and alkyl-grignard reagents with organic tellurides

Abstract Some alkyl- and aryl-tellurides react with Grignard reagents (RMgBr; R  aryl and alkyl) in the presence of NiCl 2 (PPh 3 ) 2 , NiCl 2 (Ph 2 PCH 2 CH 2 CH 2 PPh 2 ), or CoCl 2 (PPh 3 ) 2 as catalyst in THF or diethyl ehter as solvent to give the cross-coupling products together with the homo-coupling products of the tellurides in good to moderate yields, with elemental tellurium being formed as a black precipitate. A catalytic reduction-oxidation cycle involving a Ni or Co complex bearing an organotellurium moiety (RTe; R  alkenyl, aryl, and alkyl) is proposed for the reaction. Palladium catalysts such as Pd(PPh 3 ) 4 , PdCl 2 (PPh 3 ) 2 , and PdCl 2 (PhCN) 2 are revaled to be much less effective than the Ni and Co catalysts in both the yield and the stereoselectivity of the product.

Palladium-catalyzed asymmetric intermolecular arylation of cyclic or acyclic alkenes using phosphinite-oxazoline ligands derived from d-glucosamine

Abstract Chiral phosphinite-oxazolines, 2-alkyl- or 2-aryl-4,5-(4,6-O-benzylidene-3-O-(diphenylphosphino)-1,2-di-deoxy-α- d -glucopyranosyl)-[2,1-d]-2-oxazolines 1a–f derived from d -glucosamine hydrochloride, are revealed to work as effective P,N-bidentate ligands in the palladium-catalyzed enantioselective arylation of 2,3-dihydrofuran to give 2-aryl-2,5-dihydrofuran selectively in high yield with up to 96% ee. The first asymmetric phenylation reaction of trans- and cis-crotyl alcohols as acyclic alkenes with iodobenzene is also carried out to afford 3-phenylbutanal in moderate chemical yield with up to 17% ee. The complex [PdCl2(1b)] is newly prepared and its structure is characterized by X-ray crystallography. Structures of the new complex [(p-MeO2CC6H4)PdI(1a)] (8) and its cationic complex [(p-MeO2CC6H4)Pd(1a)]+OTf− (9) are also elucidated on the basis of 1H-, 13C-, and 31P-NMR spectra, p-MeO2CC6H4 moiety on the palladium being located trans to the nitrogen of 1a. This configuration might be responsible for an enantiofacial discrimination of 2,3-dihydrofuran to produce (R) isomer predominantly. The stoichiometric reaction of [PhPd(1f)]+OTf− (11) with 2,3-dihydrofuran has provided the mechanistic aspect for the arylation using P,N-ligands, in which the base-promoted deprotonation at β-position leading to an alkene(2-aryl-2,5-dihydrofuran)–palladium(0) complex has been shown to be an important step for the selective formation of the product.

Synthesis of chiral diferrocenyl diselenides and their application to asymmetric reactions

Abstract Two optically active diferrocenyl diselenides, each of which possesses two chiral centers, were newly prepared from commercial 1-(dimethylamino)ethylferrocenes and applied to induce highly enantioselective selenoxide elimination producing axially chiral allenecarboxylic esters.

Sodium tetraphenylborate as a phenylating reagent in the palladium-catalyzed phenylation of alkenes and acid chlorides

Abstract Sodium tetraphenylborate (NaBPh 4 ) reacts with terminal alkenes in acetic acid at 25°C in the presence of a catalytic amount of palladium(II) acetate together with silver acetate as a re-oxidant to give the corresponding phenylated alkenes in 22–87% yield. It also reacts with acid chlorides in tetrahydrofuran (THF) at 25°C in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium(0) to give the corresponding phenyl ketones in 51–100% yield. Carbonylation of the borate with 1–30 atm carbon monoxide (CO) in methanol at 25°C in the presence of palladium(II) acetate or sodium chloropalladate (Na 2 PdCl 4 ) affords a low yield (9–30%) of benzophenone and methyl benzoate, a higher pressure favoring the formation of the latter.

Palladium(II)-catalyzed phenylation of unsaturated compounds using phenylantimony chlorides under air ☆

Abstract Diphenylantimony chloride and phenylantimony dichloride, mainly the former, react smoothly with alkenes in acetonitrile at r.t. in the presence of a catalytic amount of Pd(OAc) 2 under air to afford the corresponding phenylated alkenes (Heck-type reaction). The addition of AgOAc as reoxidant is not necessary for this reaction in sharp contrast to similar reactions using triarylstibines. The oxygen absorption is confirmed in this catalytic reaction and the reaction does not proceed catalytically in palladium(II) under inert gases, such as nitrogen or argon. Even under air the addition of a radical scavenger stopped the reaction. The regeneration of PhPdOAc species from Ph 2 SbCl, HPdOAc species and oxygen is proposed as a key step in the catalytic cycle where oxygen-containing radical species might be present as intermediates.

Oxovanadium complex-catalyzed oxidation of propargylic alcohols using molecular oxygen

Abstract Oxovanadium complexes work as useful catalysts for the oxidation of propargylic alcohols to the corresponding carbonyl compounds in the presence of 3 A molecular sieves under an atmospheric pressure of molecular oxygen.

Synthesis and structure of novel chiral oxazolinylferrocenes and oxazolinylferrocenylphosphines, and their rhodium(I)-complexes

A variety of chiral oxazolinylferrocenes are prepared from either ferrocenecarboxylic acid or cyanoferrocene and chiral β -amino alcohols. Highly diastereoselective ortho -lithiation (84 ≈ 99% de) of the oxazolinylferrocenes is accomplished with sec -butyllithium and the treatment of the lithiated compounds with an electrophile such as Mel, Ph 2 PCI or (PhSe) 2 gives the corresponding ortho -substituted oxazolinylferrocenes. The molecular structure of ( S , S )[2-(4′-isopropyloxazolin-2′-yl)ferrocenyl]diphenylphosphine ( 10 ), ( S , S )-2-phenyl-seleno-1-(4′-isopropyloxazolinyl)ferrecene ( 17 ), ( S , R )-3-methyl-1-diphenylphosphino-2-(4′-isopropyloxazolinyl)ferrocene ( 18 ), and ( S,S,S )-[2-(4′5′-diphenyloxazolin-2′-yl)ferrocenyl]diphenylphosphine (( S,S,S )-DIPOF; 21 ) has been fully characterized by X-ray crystal-lography. In connection with their usefulness as chiral ligands for Rh(I)-catalyzed asymmetric hydrosilylation of ketones, the square planar transition metal complexes having oxazolinylferrocenylphosphines, such as [Rh(COD)(P-N)]BF 4 and Rh(CO)(P-N)Cl (P-N = 10 or 21 ), are prepared by treatment of [Rh(COD) 2 ]BF 4 and [Rh(CO) 2 Cl] 2 with 10 and 21 , respectively, and all structures have been characterized spectroscopically and further confirmed by X-ray crystallography.

Ni(II)- and Co(II)-phosphine complex catalyzed carboncarbon bond formation between organic tellurides and grignard reagents☆

Abstract Treatment of alkenyl and aryl tellurides with Grignard reagents in the presence of NiCl 2 (PPh 3 ) 2 , NiCl 2 (Ph 2 PCH 2 CH 2 CH 2 PPh 2 ), or CoCl 2 (PPh 3 ) 2 as catalyst affords the cross-coupling products together with the homo-coupling products of the tellurides in good to moderate yields under mild conditions.