Unexpected, Drastic Effect of Triflic Acid on Oxidative Diacetoxylation of Iodoarenes by Sodium Perborate. A Facile and Efficient One-Pot Synthesis of (Diacetoxyiodo)arenes

An easy, safe, and effective method for preparing (diacetoxyiodo)arenes from iodoarenes is presented. Addition of trifluoromethanesulfonic acid (triflic acid) as a promoter causes a drastic increase in the yield of (diacetoxyiodo)arenes in the reaction of iodoarenes with sodium perborate. The reaction of the iodoarenes with sodium perborate in acetic acid in the presence of triflic acid at 40−45 °C efficiently generates the corresponding (diacetoxyiodo)arenes in high yields within short time

Palladium-Catalyzed Intramolecular Hydroarylation of 4-Benzofuranyl Alkynoates. Approach to Angelicin Derivatives

Intramolecular hydroarylation of 4-benzofuranyl alkynoates using Pd­(OAc)₂ as catalyst took place selectively and efficiently, giving angular furocoumarin derivatives in high yields. The parent angelicin was obtained in 80% yield by this method. The starting 4-benzofuranyl alkynoates were easily accessible from readily available 4-hydroxybenzofurans and alkynoic acids

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

Synthesis of 1,2-Bis(trimethylsilyl)benzene Derivatives from 1,2-Dichlorobenzenes Using a Hybrid Metal Mg/CuCl in the Presence of LiCl in 1,3-Dimethyl-2-imidazolidinone

A practical and safe synthesis of 1,2-bis­(trimethylsilyl)­benzene from 1,2-dichlorobenzene and Me3SiCl was achieved by use of a hybrid metal of Mg and CuCl in the presence of LiCl in 1,3-dimethyl-2-imidazolidinone (DMI). This method does not require a toxic HMPA, provides a high yield of the product under mild conditions, and is also applied to synthesis of substituted 1,2-bis­(trimethylsilyl)­benzenes and poly­(trimethylsilyl)­benzenes

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 <i>m</i>-CPBA as a terminal oxidant

Hypervalent Iodine-Promoted α‑Fluorination of Acetophenone Derivatives with a Triethylamine·HF Complex

The direct fluorination reaction of acetophenone using iodosylarenes and TEA·5HF was conducted under mild conditions except for use of a HF reagent. The fluorination reaction was applied to acetophenone derivatives, acetonaphthones, benzyl phenyl ketone, propiophenone, butyrophenone, 1-indanone, and phenacyl chloride, giving selectively the corresponding α-fluoroketone derivatives in good yields

Reaction of Arenes with Iodine in the Presence of Potassium Peroxodisulfate in Trifluoroacetic Acid. Direct and Simple Synthesis of Diaryliodonium Triflates

Diaryliodonium triflates have been directly prepared by reaction of arenes with elemental iodine in good yields by using K2S2O8 and TFA, followed by treatment with NaOTf. This procedure avoids the use of high temperature and severe reaction conditions

Pd-Catalyzed Selective Addition of Heteroaromatic C−H Bonds to C−C Triple Bonds under Mild Conditions

Simple heteroarenes such as pyrroles and indoles undergo addition reactions to C−C triple bonds in the presence of a catalytic amount of Pd(OAc)2 under very mild conditions, affording cis-heteroarylalkenes in most cases. The cleavage of aromatic C−H bonds is the possible rate-determining step in CH2Cl2, and the addition of heteroaromatic C−H bonds to C−C triple bonds is in a trans-fashion

New Method for Preparation of Coumarins and Quinolinones via Pd-Catalyzed Intramolecular Hydroarylation of C−C Triple Bonds

A new and general method has been developed for preparation of coumarins and quinolinones by intramolecular hydroarylation of alkynes. Various aryl alkynoates and alkynanilides undergo fast intramolecular reaction at room temperature in the presence of a catalytic amount of Pd(OAc)2 in a mixed solvent containing trifluoroacetic acid (TFA), affording coumarins and quinolinones in moderate to excellent yields with more than 1000 turnover numbers (TON) to Pd. The methodology proved to tolerate a number of functional groups such as Br and CHO. On the basis of isotope experiments, a possible mechanism involving ethynyl chelation-assisted electrophilic metalation of aromatic C−H bonds by in-situ generated cationic Pd(II) species has been discussed. Also the involvement of vinylcationic species has been suggested

First [4 + 2] Cycloaddition of 1-Phenyl-1-benzothiophenium Salts with Dienes

The reaction of 1-phenyl-1-benzothiophenium triflates 1 (R = H, Me, and Ph) with cyclopentadiene successfully proceeded to give the corresponding cycloadducts, respectively, in good yields. The single-crystal X-ray analysis of 1 (R = H) showed the endo isomer. Similarly, 1,3-diphenylisobenzofuran reacted with 1 (R = H) to give the corresponding cycloadduct. These novel [4 + 2] cycloadditions of 1-phenyl-1-benzothiophenium triflates as the first example clearly indicate the olefinic nature of the thiophene ring arising from the lack of aromaticity