Teruyuki Hayashi

Synthesis of 1-tetralones by intramolecular Friedel-Crafts reaction of 4-arylbutyric acids using Lewis acid catalysts

Abstract Intramolecular Friedel–Crafts reaction of 4-arylbutyric acids efficiently proceeded in the presence of catalytic amounts of Lewis acids such as Bi(NTf 2 ) 3 and M(OTf) 3 (M=Bi, Ga, In and rare-earth metals) to form 1-tetralones. Chroman-4-one and thiochroman-4-one were also obtained in good yields from 3-phenoxypropionic acid and 3-phenylthiopropionic acid, respectively.

The asymmetric hydrocarboalkoxylation of olefins catalyzed by palladium-chiral bis(dibenzophosphole) complexes

Abstract Palladium-catalyzed asymmetric hydrocarboalkoxylation reactions of olefins have been carried out. Chiral diphosphines with rigid ring skeletons having 5H-dibenzophospholyl groups exhibited high stereoselectivity up to 52% e.e. The effects of the structure of the substrates, the diphosphine/Pd ratio, the CO pressure up to 800 kg cm−2, the R in ROH (alcohol), the solvent, and additives such as organic bases, halide salts and hydrogen have been investigated mainly for 2-phenylpropene. Higher CO pressure was favourable both for conversion and for asymmetric induction. The addition of pyridine bases increased conversion when the reaction had originally been very sluggish. Halide salts such as LiCl or bis(triphenylphosphine)iminium chloride and hydrogen at low pressures (≦ 5 kg cm−2) dramatically increased the extent of conversion without any significant decrease in the optical yield.

Hydroformylation of p-substituted styrenes catalyzed by rhodium-triphenylphosphine complexes

Abstract Rhodium-triphenylphosphine-complex-catalyzed hydroformylations of p-substituted styrenes were carried out. Increasing the δp value of the substituent raised the selectivity for 2-arylpropanal. The tendency was the opposite to that found in the absence of phosphines. Competitive reactions of p-substituted styrenes with styrene gave a linear Hammetts plot (ϱ = 0.9) of relative reactions rates vs. δp values.

Platinum–diphosphine–tin systems as active and selective hydroformylation catalysts

The activity of a platinum dichloride–phosphine–tin(II) chloride complex as a hydroformylation catalyst was dramatically enhanced by the use of diphosphine ligands which were capable of forming a strained seven-membered chelate ring; the best ligand was trans-1,2-bis(diphenylphosphinomethyl)cyclobutane, which afforded hexanals (n/iso = 99/1) from pent-1-ene with a much higher reaction rate than by the use of HRh(CO)(PPh3)3.

High catalytic activity of [HRu(CO)4]− for hydroformylation of olefins

Abstract Comparison of the catalytic activity of [HRu(CO) 4 ] − with those of the known catalyst systems ([HRu 3 (CO) 11 ] − and Ru 3 (CO) 12 ) has revealed that [HRu(CO) 4 ] − is an active catalyst for hydroformylation of 1-pentene, styrene, and ethyl acrylate. [HRu(CO) 4 ] − partly reduces the aldehydes initially formed into their corresponding alcohols. In the reaction of ethyl acrylate catalyzed by [HRu(CO) 4 ] − or [HRu 3 (CO) 11 ] − , significant amounts of carbonylative dimers (diethyl 2-formyl-2-methylglutarate and 4-ethoxycarbonyl-4-methyl-δ-valeroactone) were also formed.

Catalytic hydroformylation using dibenzophospholes as ligands

Abstract In rhodium- or cobalt-catalyzed hydroformylation, it was found that dibenzophospholes cause considerable rate enhancement in comparison with corresponding diphenylphosphines as catalyst ligands, although the dibenzophospholes behave like phosphines of strong donor ability in terms of the product distribution. The rate enhancement effect was interpreted through 13C n.m.r. spectral observations.

Efficient acid fluoride synthesis via carbonylation of organic halides

Abstract Palladium, platinum, cobalt, and rhodium triphenylphosphine complexes were found to catalyze the formation of acid fluorides via carbonylation of organic halides with fluoride salts. For palladium complex-catalyzed reactions, the use of cesium fluoride in polar solvents such as acetone and acetonitrile exhibited superior performance. The reaction took place even under an atmospheric pressure of carbon monoxide. The success of the acid fluoride synthesis is discussed in terms of the facility of oxidative addition of the starting material and the product.

Stability of phosphines under hydroformylation conditions

Abstract Phosphorus-carbon bonds of p-substituted triphenylphosphines were found to be cleaved under hydroformylation conditions in the presence of a rhodium, ruthenium, or cobalt carbonyl. Only p-isomers of the decomposition products (substituted benzaldehyde, benzyl alcohol, and/or biphenyl) were formed. The ability of metal carbonyls to cleave the PC bonds was Rh > Co > Ru. Tributylphosphine was stable under the conditions. The stability of metal carbonyl-phosphine catalyst systems was also examined and compared with the extent of PC bond cleavage.

Palladium-catalysed carbonylation of aryl halides in ionic liquid media: high catalyst stability and significant rate-enhancement in alkoxycarbonylation

Palladium-catalysed carbonylation of aryl halides with alcohols or NEt2H proceeds in ionic liquid media (1-butyl-3-methylimidazolium tetrafluoroborate or hexafluorophosphate). The catalyst/ionic liquid mixture could be recycled, after separation of the product by either distillation or extraction with ether. Carbonylation with alcohols forming benzoates was greatly accelerated by the use of ionic liquid.

Ruthenium complex-catalyzed hydrosilylation of allyl chloride with trimethoxysilane

Abstract The hydrosilylation of allyl chloride with trimethoxysilane has been examined in the presence of several homogeneous complex catalysts. Iridium and ruthenium complexes exhibit higher selectivities in the reaction to give 3-chloropropyltrimethoxysilane. Other complexes usually give propylene and/or tetramethoxysilane as side products in large quantities. The Ru3 (CO)12,-catalyzed reactions effected at lower temperatures or by using a large excess of trimethoxysilane relative to allyl chloride give the chloropropylsilane in good yields.