Mieko Arisawa

Rhodium-catalyzed synthesis of diaryl sulfides using aryl fluorides and sulfur/organopolysulfides.

Substituted pentafluorobenzenes react with sulfur to give bis(4-substituted 2,3,5,6-tetrafluorophenyl) sulfides in the presence of RhH(PPh(3))(4), 1,2-bis(diphenylphosphino)benzene (dppBz), and tributylsilane. The reaction proceeds efficiently between room temperature and 80 °C. A comparative study of the reactivities of an organic trisulfide and a tetrasulfide showed notable substrate specificity. Di-tert-butyl tetrasulfide reacted with reactive aryl monofluorides and substituted pentafluorobenzenes. Di-tert-butyl trisulfide reacted with aryl monofluorides. The reactivity was explained on the basis of the difference in S-S bond energy.

Rhodium-Catalyzed Acyl-Transfer Reaction between Benzyl Ketones and Thioesters: Synthesis of Unsymmetric Ketones by Ketone CO–C Bond Cleavage and Intermolecular Rearrangement

In the presence of catalytic amounts of RhH(CO)(PPh3)3 and 1,2-bis(diphenylphosphino)benzene (dppBz), acyl groups were transferred between benzyl ketones and thioesters/aryl esters. The rhodium complex catalyzed the cleavage of ketone CO-C bonds and intermolecular rearrangement giving unsymmetric ketones. The acyl-transfer reaction also occurred with 1-(p-chlorophenyl)-3-(p-cyanophenyl)propane-2-one giving unsymmetric ketones.

Rhodium-Catalyzed Methylthio Transfer Reaction between Ketone α-Positions: Reversible Single-Bond Metathesis of C−S and C−H Bonds

In the presence of a catalytic amount of RhH(PPh(3))(4) and 1,2-bis(diphenylposphino)ethane (dppe), alpha-phenylthio ketones were methylthiolated with p-cyano-alpha-methylthioacetophenone giving alpha-phenylthio-alpha-methylthio ketones. The methylthio transfer reaction between the ketone alpha-positions was reversible and at equilibrium, and the methylthio group was transferred in preference to the phenylthio group. The reaction of tertiary alkyl methylthiomethyl ketones proceeded in high yields; the reaction of diastereomeric 4-(tert-butyl)-2-phenylthiocyclohexanones gave an axial 2-methylthiolated product.

Stereoselective Synthesis of (E)- and (Z)-Allylphosphonium Salts by Palladium-Catalyzed Addition of Phosphine to Allene

The palladium-catalyzed addition of phosphine to allene in the presence of methanesulfonic acid stereoselectively gives the (E)- or (Z)-allylphosphonium salt. The (E)-allylphosphonium salt is formed by performing the reaction in THF under reflux and the (Z)-allylphosphonium salt is obtained at –10 °C. The (E)- and (Z)-allylphosphonium salts are used in the Wittig olefination reaction, and their diastereoselectivities are compared.

Rhodium-catalyzed cleavage reaction of aryl methyl ethers with thioesters.

A rhodium complex catalyzed the reaction of aryl methyl ethers and thioesters giving the corresponding aryl esters and methyl sulfides. S-(p-Chlorophenyl) p-(dimethylamino)benzothioate was used for the reaction of methyl aryl ethers with electron-withdrawing groups, and an S-(p-tolyl) derivative was used for those with electron-donating groups. Polymethoxybenzenes were converted to the esters in a regioselective manner.

β-Silylethenylation of phenol with silylethyne using gallium trichloride

Abstract Treatment of lithium phenoxide with silylethyne in the presence of GaCl 3 gives o -(β-silylethenyl)phenol in a high yield. The reaction involves carbogallation of phenoxygallium with silylethyne. The reaction of 2,6-disubstituted phenol with one of the substituents being t-butyl group gives ipso -substitution product. Organometallic compounds of gallium and tin, elements which sit diagonally in the periodic table, behave similarly in the carbometallation reaction.

Rhodium-Catalyzed Synthesis of Unsymmetric Di(heteroaryl) Sulfides Using Heteroaryl Ethers and S-Heteroaryl Thioesters via Heteroarylthio Exchange

Unsymmetric di(heteroaryl) sulfides were synthesized by a rhodium-catalyzed heteroarylthio exchange reaction of heteroaryl aryl ethers and S-(heteroaryl) thioesters. The reaction has broad applicability, giving diverse unsymmetric di(heteroaryl) sulfides containing five- and six-membered heteroarenes. No base is required in this reaction, which has been developed by the judicious design of organic substrates.

Rhodium-catalyzed P–P bond exchange reaction of diphosphine disulfides

A rhodium-catalyzed exchange reaction of diphosphine disulfides, a diphosphine oxide, and a diphosphine is developed. Various symmetric diphosphine disulfides containing alkyl and phenyl groups are exchanged, giving equilibrium mixtures, from which unsymmetric diphosphine disulfides are readily separated by silica gel chromatography. The resulting unsymmetric diphosphine disulfide is regioselectively added to an aldehyde.

RhCl3-CATALYZED DISULFIDE EXCHANGE REACTION OF INSULIN AND DITHIODIGLYCOLIC ACID

RhCl 3 catalyzed the alkylthio exchange reaction of insulin and dithiodiglycolic acid in water under homogeneous conditions. Insulin was rapidly consumed, and mono- and bis-exchanged insulin were formed along with the disulfide exchanged A and B chain. The disulfide bond at the A7/B7 was initially exchanged, which was followed by the A6/A11 and A20/B19 disulfides.

ortho-Vinylation reaction of anilines

N-Alkylanilines and anilines are vinylated at the ortho-position with ethyne in the presence of SnCl4–Bu3N.