Yuzo Fujiwara

Aromatic substitution of olefins. VI. Arylation of olefins with palladium(II) acetate

Olefins react with benzene derivatives to produce aryl-substituted olefins uia direct substitution of the aromatic compound for hydrogen on the double bond of the olefin in the presence of palladium salts and reduced palladium metal. The reaction may be made catalytic with respect to the palladium salts by using cupric acetate or silver acetate, and air as reoxidants. The reaction provides an extremely convenient method for the synthesis of a wide variety of olefinic compounds. xtensive studies on reactions of olefins in the presE ence of transition metal compounds have been carried out. Much less is known about arylation of olefins with transition metal compounds. Most recently, Heck described interesting arylation reactions of olefins with arylating agents such as arylmercuric halides in the presence of group VI11 metal salts, and showed that palladium salts are the most generally useful, with rhodium and ruthenium salts next best. We have reported a novel method of synthesizing stilbene derivatives by substitution of aromatic compounds for hydrogen on the double bond of the styrenepalladium chloride ~ o m p l e x . ~ In the course of our work, palladium acetate was found to be the most effective for the direct arylation of olefins with aromatic compounds in the presence of acetic acid. The present paper reports a study of substitution reaction of olefins with benzene derivatives by means of palladium salts, especially palladium acetate. A preliminary communication of a portion of this work has been given.4 ( I ) On leave of absence from Ube Industries, Ltd., Ube, Japan. (2) (a) R. F. Heck, J . Amer. Chem. Soc., 90, 5518 (1968); (b) R .F. Heck, ibid., 90, 5526 (1968); (c) R. F. Heck, ibid., 90, 5531 (1968); (d) R. F. Heck, ibid., 90, 5535 (1968); (e) R. F. Heck, ibid., 90, 5542 (1968). (3) (a) I. Moritani and Y. Fujiwara, Tefrahedron L e f f . , 1119 (1967); (b) Y . Fujiwara, I. Moritani, and M. Matsuda, Tetrahedron, 24, 4819 (1968). (4) Y. Fujiwara, I. Moritani, M. Matsuda, and S . Teranishi, Tetrahedron Lett., 633 (1968). Results and Discussion In previous papers3 we described our initial work on the reactions of the styrene-palladium(I1) chloride complex with benzene derivatives to give stilbenes. It was noted that for this arylation on a P-carbon atom of styrene, the presence of a carboxylic acid such as acetic is essential because the reactants form a homogeneous solution and the reaction proceeds best in this solvent. Further, it was found that when sodium acetate was added, the yield was greatly increased. Palladium(I1) acetate has been found to be the most generally useful, with palladium(I1) chloride-sodium acetate next best for the direct arylation of olefins with benzene derivatives. The aromatic substitution of olefins takes place in homogeneous solutions of reactant olefin and palladium(I1) acetate (equal mole equivalents to olefin) in a solution of the aromatic compound (large excess) and acetic acid. The solution is stirred in the presence of air for a few minutes to several hours (8 hr usually), to give from 10% to ca. 90% yield of arylated products, with reduced metallic palladium and a very small amount of acetates. With unsymmetrical olefins, the aryl group generally adds predominantly to the less substituted carbon atom of the double bond because of steric hindrance of the substituents. This is consistent with that observed in the Heck arylation.2 Although cis and trans mixtures are formed, no mixtures resulting from arylation in both directions to unsymmetrical olefins have been found. Increasing substitution on the olefinic carbons decreases the reactivity of the olefin in the palladium acetate arylation reaction. For example, the reaction of triphenylethylene with benzene and a palladium acetate catalyst gave tetraphenylethylene in low yield (13 %),5 while styrene reacts with benzene to afford trans-stilbene in almost quantitative yield. Results are given in Table I. (5) Yields of arylation products given in this paper are based on the amount of palladium salt utilized. Journal of the American Chemical Soc ie t y J 91:25 December 3, 1969

Palladium(II)-catalyzed carboxylation of benzene and other aromatic compounds with carbon monoxide under very mild conditions

Abstract Aromatic compounds such as benzene, toluene, chlorobenzene, anisole, and naphthalene were carboxylated by palladium(II) acetate catalyst with carbon monoxide in the presence of potassium peroxodisulfate in trifluoroacetic acid (TFA) at room temperature under atmospheric pressure. The aromatic carboxylic acids were formed in good yields; for example, the carboxylation of benzene with carbon monoxide proceeds quantitatively under the optimal conditions.

Halogenation and butylation of diamond surfaces by reactions in organic solvents

Abstract Hydrogenated diamond powder was chlorinated by treatment with sulfuryl chloride in chloroform at 50 °C. The disappearance of CH stretching peaks showed that most of the hydrogen was substituted by chlorine in this procedure. The chlorinated diamond was then reacted with butyllithium dissolved in tetrahydrofuran at 30 °C. Butyl groups incorporated onto the diamond surface were decomposed by flash pyrolysis at temperatures between 255 and 1040 °C, and all organic fragments were recovered. The fraction of butylated surface carbons to total surface carbons was calculated to be 0.055.

Palladium-catalyzed synthesis of aromatic acids from carbon monoxide and aromatic compounds via the aromatic CH bond activation

Abstract Various aromatic acids can be prepared from aromatic compounds and CO under mild conditions by Pd-based catalysts via direct aromatic CH bond activation. With PdII catalysts, the reaction is electrophilic and proceeds with ortho-para orientation when an electron-donating group is attached to the benzene ring; addition of t-BuOOH and allyl halides makes the reaction catalytic with respect to palladium(II). β-Naphthoic acid can be prepared from naphthalene and CO by the Pd/phenanthroline catalyst system in 421% yield based on Pd and in 92% selectivity.

New developments in transition metal-catalyzed synthetic reactions via C-H bond activation

Several novel and useful reactions involving transition metal-catalyzed C-H bond activation discovered in our laboratory have been summarized here, which includes olefin arylation, hydroarylation of alkynes, carboxylation of arenes and alkanes, and acetoxylation and aminomethylation of alkanes. Possible mechanisms of these reactions have been suggested.

An efficient partial oxidation of methane in trifluoroacetic acid using vanadium-containing heteropolyacid catalysts

Abstract The new catalytic system has been examined for the partial oxidation of methane in liquid phase. It was found that the vanadium containing heteropolyacids/K 2 S 2 O 8 /(CF 3 CO) 2 O/CF 3 COOH catalyst system converts methane to methyl trifluoroacetate along with a trace amount of methyl acetate in a 95% yield based on methane. The activation energy of the reaction was estimated to be 27.9 kcal mol −1 .

Palladium-catalyzed one-step synthesis of aromatic acids from aromatic compounds with carbon monoxide

Abstract One-step carboxylation of aromatic compounds such as benzene, anisole, and naphthalene with carbon monoxide giving the corresponding aromatic acids, has been found to proceed catalytically using the Pd(OAc) 2 /t-BuOOH/CH 2 =CHCH 2 Cl system.

Synthesis of a new hypervalent iodine compound, [2-(hydroxydimethylsilyl)phenyl](phenyl)iodonium triflate as a convenient approach to benzyne

Abstract A new benzyne precursor, [2-(hydroxydimethylsilyl)phenyl](phenyl)iodonium triflate, is prepared from 1,2-dibromobenzene in good yield. This procedure avoids the use of carcinogenic HMPA and the severe reaction conditions. The reaction of the benzyne precursor with Bu 4 NF in the presence of a trapping agent under very mild conditions efficiently generates benzyne and gives the benzyne adduct in high yield.

Novel heteroaromatic CH insertion of alkylidenecarbenes. A new entry to furopyridine synthesis

Abstract Reaction of alkynyl(phenyl)iodonium tosylates with 4-hydroxypyridine and 3-hydroxypyridine in the presence of potassium tert-butoxide undergoes a novel heteroaromatic CH insertion of alkylidenecarbenes generated in situ to give the corresponding furopyridine derivatives. The heteroaromatic CH insertion shows an extremely high selectivity compared with the possible aliphatic CH insertion. This process is also applied to furoquinoline synthesis.

Palladium-catalyzed acetic acid synthesis from methane and carbon dioxide

Publisher Summary Carbon dioxide is one of the natural C1-resources that is being watched with keenest interest as a substitute of toxic CO in the C1-chemistry. The chemical fixation of CO2, a process which is appealing for both scientific and environmental reasons since methane and CO2 are well known as the greenhouse gases, is an important task for the human being though it is difficult because of low reactivity of CO2. Alkane activation/functionalization by transition metals under mild conditions is also one of the most challenging problems in modern chemistry since small alkanes including methane, ethane, and propane are the most abundant natural resources of hydrocarbons.