Juzo Oyamada

Hypervalent Iodine-Mediated Fluorination of Styrene Derivatives: Stoichiometric and Catalytic Transformation to 2,2-Difluoroethylarenes.

Fluorination of styrene derivatives with a reagent system composed of μ-oxo-bis[trifluoroacetato(phenyl)iodine] and a pyridine·HF complex gave the corresponding (2,2-difluoroethyl)arenes in good yields. Similarly, the reagent of PhI(OCOCF3)2 and the pyridine·HF complex acted as a fluorinating agent for styrene derivatives. The fluorination of styrene derivatives with the pyridine·HF complex underwent under catalytic conditions using 4-iodotoluene as a catalyst and m-CPBA as a terminal oxidant.

Drastic effect of bidentate phosphine ligands on Pd-catalyzed hydroarylation of ethyl propiolate: a simple route to arylbutadienes

Palladium complexes with bidentate phosphine ligands, Pd(dppe)(OAc)(2) and Pd(dppm)(OAc)(2), were found to be effective catalysts for reactions of simple arenes with ethyl propiolate, affording arylbutadiene derivatives selectively.

Palladium-Catalyzed Desilylative Acyloxylation of Silicon–Carbon Bonds on (Trimethylsilyl)arenes: Synthesis of Phenol Derivatives from Trimethylsilylarenes

A strategy for desilylative acetoxylation of (trimethylsilyl)arenes has been developed in which (trimethylsilyl)arenes are converted into acetoxyarenes. The direct acetoxylation is performed in the presence of 5 mol % of Pd(OAc)2 and PhI(OCOCF3)2 (1.5 equiv) in AcOH at 80 °C for 17 h. The acetoxyarenes are obtained in good to high yields (67-98%). The synthetic utility is demonstrated with a one-pot transformation of (trimethylsilyl)arenes to phenols by successive acetoxylation and hydrolysis. Furthermore, desilylative acyloxylation of 2-(trimethylsilyl)naphthalene using several carboxylic acids has been conducted.

Practical and convenient synthesis of coumarins from phenols and propiolic acid esters

This protocol describes the synthesis of 6,7-methylenedioxy-4-phenylcoumarin from sesamol and ethyl phenylpropiolate using a Pd(OAc)2 catalyst to illustrate coumarin synthesis. This procedure is simple and easy and can be applied to the synthesis of other coumarins that have electron-rich phenol groups. The reaction is conducted by stirring a solution of Pd(OAc)2, sesamol and ethyl phenylpropiolate in trifluoroacetic acid at room temperature (15–20 °C) under atmospheric conditions. This protocol can be completed in 3 d.

Convenient synthesis of ethylene carbonates from carbon dioxide and 1,2-diols at atmospheric pressure of carbon dioxide

ABSTRACT An efficient and convenient synthesis of ethylene carbonates was achieved by the reaction of carbon dioxide with 1,2-diols in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), followed by treatment with 1-bromobutane. This DBU-promoted transformation proceeded at an atmospheric pressure of carbon dioxide at 25 °C and gave ethylene carbonates in good yields. GRAPHICAL ABSTRACT

A Convenient Synthesis of 2-Fluoro- and 2-Chloromalonic Esters Mediated by Hypervalent Iodine

Direct fluorination of malonic esters with a reagent system of iodosylbenzene and Et3N·5HF gave the corresponding 2-fluoromalonic esters in good to high yields. Direct chlorination using iodosylbenzene and hydrochloric acid also provided the 2-chloromalonates in high yields.

Synthesis of β-Fluorovinyliodonium Salts by the Reaction of Alkynes with Hypervalent Iodine/HF Reagents

The reaction of alkynes with PhIO and Py·HF followed by treatment with BF3·OEt2 gave β-fluorovinyliodonium tetrafluoroborates in good to high yields. More conveniently, the reaction using PhI and Py·HF in the presence of m-CPBA also afforded β-fluorovinyliodonium tetrafluoroborates in good yields. These methods have the advantages that β-fluorovinyliodonium salts can be prepared without ArIF2.

Difluorination of Functionalized Aromatic Olefins Using Hypervalent Iodine/HF Reagents

The hypervalent iodine/HF reagent consisting of PhIO and HF·py was found to be effective for fluorination of functionalized aromatic olefins bearing synthetically important carbonyl and hydroxyl groups. Fluorination of 1,3-diphenyl-2-propen-1-one with PhIO/HF·py reagent in CH2Cl2 at room temperature gave 3,3-difluoro-1,2-diphenyl-1-propanone in high yield. Other α-aryl-α,β-unsaturated ketones underwent the fluorination to yield aryl 2,2-difluoroethyl ketone derivatives in good to high yields. Catalytic fluorination of α-aryl-α,β-unsaturated ketones using a p-TolI/HF·py/mCPBA reagent system also worked well. Moreover, the fluorination of cinnamyl alcohol derivatives by PhIO/HF·py reagent proceeded smoothly to afford 2-aryl-3,3-difluoro-1-propanols in moderate yields.

A Convenient Synthesis of 3,3-Bis(thienyl)propionic Acids by Platinum (II)-Catalyzed Reaction of Thiophenes with Propiolic Acids

Platinum(II)-catalyzed hydroarylation of propiolic acids was applied to thiophenes, and we found that the reaction with thiophenes predominantly afforded double thienylated products. Reaction of thiophenes with ethyl propiolate proceeded efficiently in the presence of K2PtCl4 (2 mol%) and AgOTf (8 mol%) in trifluoroacetic acid under mild conditions to give ethyl 3,3-bis(substituted thienyl)propionates in good yields. The same platinum(II)-catalyzed reaction with propiolic acid instead of the ethyl ester provided bis(substituted thienyl)propionic acids in high yields.