Yoshiki Okamoto

Use of allysilanes as a new type of silylating agent for alcohols and carboxylic acids

Abstract A new convenient route to silyl ethers and esters from alcohols and carboxylic acids using allylsilanes in the presence of an acid catalyst in acetonitrile was developed. The present method is also applicable to t-butyldimethylsilylation.

Novel method for dealkylation of esters, ethers, and acetals by chlorotrimethylsilane–sodium iodide

Reactions of the carboxylic esters (1) and the ethers (5) with chlorotrimethylsilane (2) in the presence of sodium iodide give the silyl derivatives (3) and (6) quantitatively which are easily converted into the corresponding carboxylic acids (4) and phenols (7) under mild conditions.

Preparation and structure of ()-(−)- and ()-(+)-2,2′-(2,2-dimethyl-2-silapropane-1,3-diyl)-1,1′binaphthalene

The title axially dissymmetric organosilicon compound is obtainable in optically pure from by synthesis of the racemate followed by resolution with a chiral poly(triphenylmethyl methacrylate) column. The structure has been established by spectroscopic and single crystal X-ray diffraction methods.

Photochemical carbon–phosphorus bond cleavage of nitro-substituted benzylphosphonic acids

Upon u.v.-irradiation, the C–P bond of p-nitrobenzylphosphonate is more readily cleaved to give a monomeric metaphosphate anion as intermediate than those of o- and m-derivatives.

PHOTOLYSIS OF ARYL ESTERS OF TRI- AND TETRACOORDINATE PHOSPHORUS COMPOUNDS

Abstract Upon. UV excitation in methanol, some diaryl esters of alkyl- or alkenylphosphonates underwent an elimination of two aryl groups to give biaryls and the corresponding alkyl- or alkenylphosphonic acids. Tris(4-methoxyphenyl) phosphite also underwent a similar elimination to give 4,4′-dimethoxybiphenyl and 4-methoxyphenyl phosphonate. This interesting biaryl elimination was confirmed to proceed via a singlet intramolecular excimer by means of fluorescence spectra and Stern-Volmer analysis.

CONVENIENT SYNTHETIC ROUTE TO MONO-OR DIALKYL PHOSPHATE FROM INORGANIC PHOSPHORUS ACIDS

Abstract Mono- or dialkyl phosphate was synthesized in a favorable yield by oxidation of phosphonic or phosphinic acid in alcohol with oxygen at the presence of a catalytic amount of copper (II) chloride. The reaction may proceed via the formation of corresponding phosphorochloridate or phosphorochloridite.

PHOTOCHEMICAL C[sbnd]P BOND CLEAVAGE OF BENZOYLBENZYLPHOSPHONIC ACIDS

Abstract Benzoylbenzylphosphonic acids (p- and m-) easily underwent photochemical C[sbnd]P bond cleavage in a basic aqueous ethanol solution to give methylbenzophenone, orthophosphate, and ethyl phosphate.

Photolysis of bis(methoxyphenyl) methylphosphonates

Abstract On UV irradiation in methanol, bis(methoxyphenyl) methylphosphonates undergo ipso coupling of two methoxyphenyl groups or intramolecular rearrangement of a methoxyphenyl group to give dimethoxybiphenyl and trimethoxybiphenyl respectively. They exhibit two emission bands attributed to a monomeric excited methoxyphenyl group and an intramolecular excimer. Their fluorescence spectra and reactivities are affected by the position of the methoxyl group on the benzene ring. The intramolecular excimer of bis(3-methoxyphenyl) methylphosphonate is more polar than that of bis(4-methoxyphenyl) methylphosphonate, because the former has a more unsymmetrical aryl group than the latter. Dimethoxybiphenyl may be formed through a non-polar intramolecular excimer, while trimethoxybiphenyl may be formed through a polar excimer or a monomeric excited state. The reactivities also depend on the position of the methoxylgroup and decrease in the order 4->3->2-methoxyphenyl.

FORMATION OF INTRAMOLECULAR EXCIMER IN ARYL PHOSPHATES AND THEIR REACTIVITIES

The fluorescence spectra of bis(4‐methoxyphenyl) hydrogen phosphate and tris(4‐meth‐oxyphenyl) phosphate showed two emission bands. A longwavelength emission band arose from the intramolecular excimer of two 4‐methoxyphenyl groups and a short band arose from a 4‐methoxyphenyl group itself. There was a good correlation between the relative intensity of the monomer/excimer emissions and the quantum yield of 4,4′‐dimethoxybiphenyl, which was an intramolecular coupling product.

PHOTOSUBSTITUTION OF METHOXYPHENYL PHOSPHATES

Abstract Photosubstitution of diethyl methoxyphenyl phosphate with some nucleophiles (Cl−, Br−, CN−) in methanol gave the corresponding 4-chloro-, 4-bromo-, and 4-cyanomethoxybenzenes through a singlet excited state. In acidic media, the reaction was accelerated. Upon further irradiation, halo-substituted methoxybenene underwent dehalogenation to give methoxybenzene. Methoxybenzene also formed directly through the homolytic PO-Ar bond cleavage. The order of reactivities of the isomers of the phosphate was 4->2->3-methoxyphenyl derivatives.