Direct Carbon–Carbon Bond Formation from Alcohols and Active Methylenes, Alkoxyketones, or Indoles Catalyzed by Indium Trichloride

Propargylation of 1,3-dicarbonyl compounds with 1,3-diarylpropynes via oxidative cross-coupling between sp3 C-H and sp3 C-H

A highly efficient oxidative-coupling reaction between diarylpropargylic sp(3) C-H and active methylenic sp(3) C-H was achieved with DDQ as oxidant. The reaction afforded a direct method for the propargylation of 1,3-dicarbonyl compounds, thus providing a concise synthesis of the corresponding products.

The lewis acidic ruthenium-complex-catalyzed addition of beta-diketones to alcohols and styrenes is in fact Brønsted acid catalyzed

The perchlorate salt of the dicationic bipy-ruthenium complex cis-[Ru(6,6'-Cl2bipy)2(H2O)2]2+ effectively catalyzes addition of beta-diketones to secondary alcohols and styrenes to yield the alpha-alkylated beta-diketones. In a catalytic addition reaction of acetylacetone to 1-phenylethanol, the kappa2-acetylacetonate complex [Ru(6,6'-Cl2bipy)2(kappa2-acac)]ClO4 was isolated after the catalysis; this complex is readily synthesized by reacting cis-[Ru(6,6'-Cl2bipy)2(H2O)2](ClO4)2 with acetylacetone. [Ru(6,6'-Cl2bipy)2(kappa2-acac)]ClO4 is unreactive toward 1-phenylethanol in the presence of HClO4; it also fails to catalyze the addition of acetylacetone to 1-phenylethanol. On the basis of these observations, it is proposed and confirmed by independent experiments that the catalytic addition of beta-diketones to the secondary alcohols is in fact catalyzed by the Brønsted acid HClO4, which is generated by the reaction of cis-[Ru(6,6'-Cl2bipy)2(H2O)2](ClO4)2 with the beta-diketone.

High-surface-area TiO2 and TiN as catalysts for the C-C coupling of alcohols and ketones

To design more sustainable processes for the alkylation of ketones, the use of both atom-ineffective leaving groups such as halides and boron as well as noble-metal-based catalysts should be avoided. For that purpose, high-surface-area titanium nitride was prepared from high-surface-area titanium dioxide using cyanamide as a transcription agent. The resulting nitride as well as the initial oxide proved to be effective and versatile catalysts for the alkylation of ketones with alcohols. Interestingly, the TiN catalyst yields unsaturated compounds, while the oxide-based catalyst mainly yields saturated coupling products. As a result of its metallic properties, TiN shows a strong tendency to catalyse the dehydrogenation of alcohols, which then undergo aldol condensation with ketones. In contrast, TiO(2) promotes the direct nucleophilic attack of ketones on alcohols.

InCl3/I2-Catalyzed Cross-Coupling of Alkyl Trimethylsilyl Ethers and Allylsilanes via an in Situ Derived Combined Lewis Acid of InCl3 and Me3SiI

Direct Csp3-Csp3 coupling of various aliphatic trimethylsilyl ethers and allylsilanes is effectively catalyzed by InCl3 and I2. The transformation is thought to involve an in situ-derived combined Lewis acid of InCl3 and Me3SiI. The reaction can be used for the construction of quaternary-quaternary and quaternary-tertiary carbon-carbon bonds. This system enabled a highly chemoselective coupling to be conducted with a trimethylsilyl ether including an aryl halide moiety. Furthermore, couplings were possible using an alkynyltrimethylsilane and a trimethylsilyl ketene acetal.

A highly alpha-regioselective AgOTf-catalyzed nucleophilic substitution of the Baylis-Hillman acetates with indoles

An efficient method for highly alpha-regioselective nucleophilic substitution of the Baylis-Hillman acetates with indoles catalyzed by AgOTf in high yields (72-99%) has been developed. Reductive cyclization of the substitution products furnished the azepinoindole derivatives in good yields (up to 93%).