Palladium- or nickel-catalyzed cross coupling. A new selective method for carbon-carbon bond formation

Hydrozirconation has recently been developed as a procedure for functionalizing alkenes, alkynes, and 1,3-dienes via organozirconium(IV) intermediates. These intermediates react with a variety of electrophilic reagents to give organic products in high yield. Mechanisms of reactions involved in these sequences are discussed.

Hydrozirconation: A New Transition Metal Reagent for Organic Synthesis

reactions constituted an important breakthrough in the application of radical chemistry in organic synthesis.2 An important and very attractive feature of these reactions is their high degree of functional group tolerance. Since radicals are usually stable under protic conditions, alcohols or even water can, in principle, be used as solvents in radical chemistry. Consequently, protic functional groups do not need protection. As soon as the underlying principles of the kinetic and thermodynamic behavior of free radicals were firmly established, efficient synthetic applications became feasible.3 The use of chain reactions has resulted in a number of very impressive total syntheses of natural products. An example is shown in eq 1.4 The characteristic features of free radicals can by now be deduced from ESR data.5 The course of some radical reactions can be understood by theoretical means.6

Reagent-Controlled Transition-Metal-Catalyzed Radical Reactions

Safe Preparation and Purification of Sodium Tetrakis[(3,5-trifluoromethyl)phenyl]borate (NaBArF24): Reliable and Sensitive Analysis of Water in Solutions of Fluorinated Tetraarylborates

The preparatively important catalytic opening of epoxides to β-titanoxy radicals via single-electron transfer (SET) is described. These radicals can be reduced to alcohols or participate in C−C bond-forming reactions. A key step in the catalytic cycle is the conceptually novel protonation of titanium−oxygen and −carbon bonds. Our method combines the advantages of radical reactions, e.g., high functional group tolerance and stability of radicals under protic conditions, with the ability of organometallic complexes to determine the course of transformations in reagent-controlled reactions.

PC Wailes

Papers

Insertion reactions of dicyclopentadienyldimethylzirconium and related cyclopentadienyl compounds with sulphur dioxide and nitric oxide

Dimeric dicyclopentadienyltitanium(III) halides

Hydrido complexes of zirconium

Sulphur dioxide insertion reactions with dicyclopentandienyltitanium and -zirconium alkyl and aryl compounds

Hydrido complexes of zirconium IV. Reactions with olefins