Yasushi Nishihara

Palladium‐Catalyzed Direct Thiolation of Aryl CH Bonds with Disulfides

A catalytic variant of the direct thiolation of arenes, bearing directing groups, with disulfides or thiols has been developed under palladium and copper co-catalysis. Both sulfenyl moieties of the disulfide could be incorporated into the thiolated products, therefore, the reactions reached completion with only half an equivalent of disulfide, with respect to the starting arene. Experimental evidence suggested that the reaction proceeds through a Pd(II)/Pd(IV) mechanism.

Palladium-Catalyzed peri-Selective Chalcogenation of Naphthylamines with Diaryl Disulfides and Diselenides via C–H Bond Cleavage

A palladium-catalyzed and picolinamide-directed C-H thiolation of naphthylamine derivatives with diaryl disulfides has been developed to provide a convenient route to 8-sulfenyl-1-naphthylamines. The reaction proceeds via a 5-membered palladacycle intermediates to afford the peri-thiolated products exclusively, in contrast to the conventional ortho-functionalization. Moreover, the related direct selenation was also achieved with diaryl diselenides, giving the corresponding selenated products with perfect site-selectivity.

Iron-Catalyzed Oxidation of Tertiary Amines: Synthesis of β-1,3-Dicarbonyl Aldehydes by Three-Component C–C Couplings

β-1,3-Dicarbonyl aldehydes were synthesized by iron-catalyzed oxidative reactions between 1,3-dicarbonyl compounds and two molecules of tertiary amines in the presence of tert-butyl hydroperoxide (TBHP). α,β-Unsaturated aldehydes generated by tertiary amine oxidation in situ act as key intermediates under mild reaction conditions.

A novel C-C bond forming reaction of aryl- and alkenylsilanols. A halogen-free mizoroki-heck type reaction

Abstract When dimethyl(phenyl)silanol is subjected to on electron-deficient olefin in the presence of a stoichiometric amount of Pd(OAc)2, substitution of the CH bond of the olefin by a phenyl group on the silanol occurs in 52–86% yields. The reactions of several aryl- and alkenylsilanols with several olefins are also found to proceed in the system of 10 mol% of Pd(OAc)2, Cu(OAc)2 (3 mol), LiOAc (2 mol) to give the corresponding products in up to 69% yield.

Chelate-assisted direct selenation of aryl C-H bonds with diselenides catalyzed by palladium.

A direct selenation of inert C-H bonds of benzamide derivatives and their related compounds with diselenides has been achieved with the palladium catalyst. The reaction was compatible with a variety of functional groups, including a bromo group. Primitive mechanistic insights revealed that the reaction proceeded through a C-H bond cleavage and the sequential oxidative addition of diselenides. The present synthetic method can be applied to the facile synthesis of selenoxanthone which can be regarded as promising heterocyclic materials.

Convenient preparative method of α,β-disubstituted cyclopentenone by zirconium promoted intermolecular coupling of an alkyne, EtMgBr (or ethylene) and CO

Abstract Treatment of Cp2ZrCl2 with 2 equiv of EtMgBr in THF, followed by addition of an internal alkyne and subsequent treatment with COI2 gave α,β-disubstituted cyclopentenone in good to high yields. When a conjugated enyne was used as an alkyne component, α-alkenyl cyclopentenone was selectively formed in 80–89% yields. In the case of 4,6-decadiyne, α-alkynylcyclopentenone was formed in 88% yield. Bridged alkynes such as 1,4-dihexynylbenzene afforded α,α′-bridged cyclopentenone compounds in good yields.

Conjugate reduction of α,β-unsaturated ketones with hydrosilane mediated by copper(I) salt

Abstract Reduction of several α,β-unsaturated ketones with dimethylphenylsilane and 10–100 mol% of CuF(PPh3)3·2EtOH or CuCl/PPh3/Bu4NF proceeds in a 1,4-selective manner to give the corresponding saturated ketones in up to >99% yield.

Synthesis of multisubstituted olefins through regio- and stereoselective silylborylation of an alkynylboronate/chemoselective cross-coupling sequences.

A highly regio- and stereoselective silylborylation of an alkynylboronate is disclosed. PhMe2Si-B(pin) undergoes a Pd(OAc)2/(t)OctNC-catalyzed syn-addition to the alkynylboronate to yield 1-phenyl-1-silyl-2,2-diborylethene with high regioselectivity. The product 1-phenyl-1-silyl-2,2-diborylethene is then chemoselectively arylated by Suzuki-Miyaura coupling to afford (Z)-1-silyl-2-borylstilbene derivatives. This approach is extended to the synthesis of a tetraarylated olefin with four different substituents.

Iron‐Induced Regio‐ and Stereoselective Addition of Sulfenyl Chlorides to Alkynes by a Radical Pathway

The radical addition of the Cl-S σ-bond in sulfenyl chlorides to various C-C triple bonds has been achieved with excellent regio- and stereoselectivity in the presence of a catalytic amount of a common iron salt. The reaction is compatible with a variety of functional groups and can be scaled up to the gram-scale with no loss in yield. As well as terminal alkynes, internal alkynes underwent stereodefined chlorothiolation to provide tetrasubstituted alkynes. Preliminary mechanistic investigations revealed a plausible radical process involving a sulfur-centered radical intermediate via iron-mediated homolysis of the Cl-S bond. The resulting chlorothiolation adducts can be readily transformed to the structurally complex alkenyl sulfides by cross-coupling reactions. The present reaction can also be applied to the complementary synthesis of the potentially useful bis-sulfoxide ligands for transition-metal-catalyzed reactions.

Applied Cross-Coupling Reactions

Metal-Catalyzed Cross-Coupling Reactions.- A Historical Overview of Metal-Catalyzed Cross-Coupling Reactions.- Mechanism and Fundamental Reactions.- Applications of Cross-Coupling Reactions.- Natural Product Synthesis.- Pharmaceuticals.- Liquid Crystals.- Conjugated Polymers.- Recent Advances in Cross-Coupling Reactions.- With Aryl Chlorides, Tosylates, and Methylates.- With Alkyl Electrophiles.