Nickel-promoted alkylative or arylative carboxylation of alkynes

[reaction: see text]. Nickel-promoted alkylative or arylative carboxylation of terminal alkynes via a carbon dioxide fixation process was investigated. In the presence of a stoichiometric amount of a zero-valent nickel complex, the reaction of alkynes with CO2 gave a nickelacycle, which was reacted with various organozinc reagents under very mild conditions to provide beta,beta'-disubstituted, alpha,beta-unsaturated carboxylic acids in a highly regio- and stereoselective manner.     

Asymmetric reduction of the carbonyl group by chiral hydrides. 1. Stereochemical considerations

Conclusions A quadrant rule is proposed for the enantioselective reduction of acetophenone by chiral hydrides based on LiAlH₄, NaBH₄, LiBH₄, and BH₃. This enables the configuration of the product to be explained and predicted, depending on the preferred conformations of the ligands in these hydrides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 843–848, April, 1987.     

Selective reduction of carbonyl compounds by diphenylstibine

Carbonyl compounds were selectively reduced by diphenylstibine in the presence of Lewis acid.     

Reactions of polyfluorinated 2,5-cyclohexadienones at the carbonyl group

Perfluoro-4-phenoxy-2,5-cyclohexadienone reacts with phenyl- and pentanuorophenylhydrazines to give products of nucleophilic substitution of the fluorine atom at the double bond, 3-arylazotetrafluorophenols. In the presence of aluminum chloride, the reactions proceed at the carbonyl groups of polyfluorinated cyclohexadienones to form the corre sponding polyfluorinated azobenzenes. Perfluoro-4-phenoxy-2,5-cyclohexadierione reacts with butyllithium and butylmagnesium bromides to give the product of addition at the carbonyl group.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1778–1781, July, 1996.     

Titanium-mediated alkylative coupling of N-acylpyrroles

[reaction: see text]. Inter- and intramolecular titanium-mediated coupling reactions of N-acylpyrroles are reported for convenient functionalization of terminal olefins. Comparison with the Kulinkovich reaction of esters and other carboxylic acid derivatives is also included.     

Novel photolabile protecting group for carbonyl compounds

[reaction: see text] A novel type of photo-protecting group for carbonyl compounds is described. The protecting group is readily accessed in one step from commercially available material. Installation of the protecting group upon the carbonyl compounds is achieved in excellent yields. The carbonyl compounds in their protected form are remarkably stable under various conditions and can be released photochemically in high efficiency.     

Oxidation with a photolabile carbonyl protecting group

A novel oxidation approach utilizing a robust photolabile carbonyl protecting group reagent (1) as the oxidizing reagent has been developed. Different from existing methods, this approach oxidizes primary alcohols to the photosensitive acetals (e.g., 3), providing another unique approach to the protected aldehydes. Thus, for the first time, oxidation and protection are achieved in one reaction. Secondary alcohols are oxidized to the corresponding ketones. Moreover, the photolabile protecting group (PPG) also oxidizes ethers and esters. The oxidation is presumably via hydride abstraction by the tritylium ion generated from 1 under acidic conditions. However, the mechanisms for primary alcohols and secondary alcohols are slightly different.     

The reduction of osmium carbonyl clusters by nitriles

The clusters Os₆(CO)₁₈ Os₇(CO)₂₁ and Os₈(CO)₂₃ are reduced to the anoins [Os₆(CO)₁₈]^2?, [Os₇(CO)₂₀]^2? and [Os₈(CO)₂₂]^2?, respectively, by the action of nitriles RCN (R = Me, Et, CH₂C(Me)); the kinetics of the reaction of Os₆(CO)₁₈ with EtCN have been examined and reveal a third order dependence on nitrile concentration.     

Photo-enhanced reduction of carbonyl compounds by sodium borohydride

The reduction of ketones and some esters by sodium borohydride is dramatically accelerated by uv irradiation. The reaction seems to proceed from the (n, π) excited state of the carbonyl compound. The photocatalytic effect is dependent on the solvent polarity and substituents on aromatic carboxylic acids and alcohols of esters.