There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Ru-, Rh-, and Pd-Catalyzed C-C Bond Formation Involving C-H Activation and Addition on Unsaturated Substrates: Reactions and Mechanistic Aspects

Catalytic C–H activation has emerged as a powerful tool for sustainable syntheses. In the recent years, notable success was achieved with the development of cobalt-catalyzed C–H functionalizations with either in situ generated or single-component cobalt-complexes under mild reaction conditions. Herein, recent progress in the field of organometallic cobalt-catalyzed C–H activation is reviewed until November 2015.

Cobalt-Catalyzed C―H Activation

The development of new methods for the direct functionalization of unactivated C–H bonds is ushering in a paradigm shift in the field of retrosynthetic analysis. In particular, the catalytic enantioselective functionalization of C–H bonds represents a highly atom- and step-economic approach toward the generation of structural complexity. However, as a result of their ubiquity and low reactivity, controlling both the chemo- and stereoselectivity of such processes constitutes a significant challenge. Herein we comprehensively review all asymmetric transition-metal-catalyzed methodologies that are believed to proceed via an inner-sphere-type mechanism, with an emphasis on the nature of stereochemistry generation. Our analysis serves to document the considerable and rapid progress within in the field, while also highlighting limitations of current methods.

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Catalytic Enantioselective Transformations Involving C-H Bond Cleavage by Transition-Metal Complexes.

Electrochemical oxidation of 1-alkenylarenes to give benzaldehyde dimethyl acetals

1.

During the oxidative cyanation of 2-, 3-, and 4-methylcyclohexanones in the Na2S2O8-NaCN system the corresponding 4-cyano(methyl)cyclohexanones are formed regiospecifically.




2.

The oxidative cyanation of 2- and 3-methylcyclohexanones takes place diastereoselectively with the formation of trans- and cis-4-cyano-2(3)-methylcyclohexanones in a ratio of 1.5∶1 (or 2∶1). The selectivity of cyanation is determined by the bridge structure of the intermediate 4-oxo(methyl)cyclohexyl radicals, which are the precursors of the 4-cyanocyclohexanones.

Stereochemistry of the remote oxidative cyanation of methylcyclohexanones

A method was developed for the synthesis of hydroxy carboxylic acids by the addition of saturated alcohols and acids to 10-undecenoic acid and 10-undecen-1-ol.

Free-radical addition of alcohols and acids to 10-undecenoic esters, 10-undecen-1-Ol, and 10-undecenyl acetate

1.

Anisole, toluene, chlorobenzene, ethyl benzoate, and benzonitrile have been substituted in the aromatic nucleus by the CH3COCH2 radical, generated in the redox system acetone-Mn(OAc)3-AcOH at 70°. The acetonyl radical displays electrophilic properties in this reaction.




2.

The radical reaction of acetone with thiophene proceeds selectively at the α-carbon atom of the thiophene ring to form 1-(2-thienyl)propan-2-one.

Radical reaction of acetone with aromatic compounds

The selective oxidative 1,2-addition of acetylacetone and other dicarbonyl compounds to conjugated dienes was realized in an acetic acid solution containing manganese(III) and copper(II) ions. A series of 5-(1-alkenyl)-substituted 4,5-dihydrofurans were synthesized by the reaction with yields of 30–97%.

G. I. Nikishin

Papers

Electrochemical oxidation of 1-alkenylarenes to give benzaldehyde dimethyl acetals

Stereochemistry of the remote oxidative cyanation of methylcyclohexanones

Free-radical addition of alcohols and acids to 10-undecenoic esters, 10-undecen-1-Ol, and 10-undecenyl acetate

Radical reaction of acetone with aromatic compounds

Oxidative addition of 1,3-dicarbonyl compounds to dienes in the presence of Mn(III) AND Cu(II) acetates