Radikale und Übergangsmetallkatalyse – eine Allianz par excellence zur Steigerung von Reaktivität und Selektivität in der organischen Chemie

The atom-transfer carbonylation reaction of various alkyl iodides thereby leading to carboxylic acid esters was effectively accelerated by the addition of transition-metal catalysts under photoirradiation conditions. By using a combined Pd/hν reaction system, vicinal C-functionalization of alkenes was attained in which α-substituted iodoalkanes, alkenes, carbon monoxide, and alcohols were coupled to give functionalized esters. When alkenyl alcohols were used as acceptor alkenes, three-component coupling reactions, which were accompanied by intramolecular esterification, proceeded to give lactones. Pd-dimer complex [Pd(2)(CNMe)(6)][PF(6)](2), which is known to undergo homolysis under photoirradiation conditions, worked quite well as a catalyst in these three- or four-component coupling reactions. In this metal/radical hybrid system, both Pd radicals and acyl radicals are key players and a stereochemical study confirmed the carbonylation step proceeded through a radical carbonylation mechanism.

Section: Resultssupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Pd/Light‐Accelerated Atom‐Transfer Carbonylation of Alkyl Iodides: Applications in Multicomponent Coupling Processes Leading to Functionalized Carboxylic Acid Derivatives

Fusano

Sumino

Nishitani

et al. 2012

“…[10,11] The classical radical methods for biaryl synthesis are known as the Gomberg-Bachmann and Pschorr reactions, [12,13] in which aryl diazonium salts serve as precursors for aryl radicals. New developments in this area include the use of aryl halides in the presence of organotin, organosilicon, or samarium compounds.…”

Section: Introductionmentioning

confidence: 99%

Radical Arylation of Phenols, Phenyl Ethers, and Furans

Wetzel

Pratsch

Kolb

et al. 2010

108

Radical arylations of para-substituted phenols and phenyl ethers proceeded with good regioselectivity at the ortho position with respect to the hydroxy or alkoxy group. The reactions were conducted with arenediazonium salts as the aryl radical source, titanium(III) chloride as the reductant, and diluted hydrochloric acid as the solvent. Substituted biaryls were obtained from hydroxy- and alkoxy-substituted benzylamines, phenethylamines, and aromatic amino acids. The methodology described offers a fast, efficient, and cost-effective new access to diversely functionalized biphenyl alcohols and ethers. Free phenolic hydroxy groups, aromatic and aliphatic amines, as well as amino acid substructures, are well tolerated. Two examples for the applicability of the methodology are the partial synthesis of a beta-secretase inhibitor and the synthesis of a calcium-channel modulator.

“…[11,12] In contrast with other protocols, ketones are also substrates of this reaction. The success of our strategy was based on combina-tion of the free-radical chemistry mediated by Ti III [13][14][15][16] with the late-transition-metal chemistry mediated by Pd. The excellent chemical profile of allyltitanium complexes towards aldehydes and ketones is at the heart of the chemoselectivity of the process.…”

Section: Introductionmentioning

confidence: 99%

Ti/Pd Bimetallic Systems for the Efficient Allylation of Carbonyl Compounds and Homocoupling Reactions

Millán

Campaña

Bazdi

et al. 2011

The allylation, crotylation and prenylation of aldehydes and ketones with stable and easily handled allylic carbonates is promoted by a Ti/Pd catalytic system. This Ti/Pd bimetallic system is especially convenient for the allylation of ketones, which are infrequent substrates in other related protocols, and can be carried out intramolecularly to yield five- and six-membered cyclic products with good stereoselectivities. In addition, Ti/Pd-mediated reductions and Würtz-type dimerisation reactions can be readily carried out from allyl carbonates and carboxylates.