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

• Published in: Chemistry : a European journal 2012-07, Vol.18 (30), p.9415-9422
• Main Authors: Fusano, Akira, Sumino, Shuhei, Nishitani, Satoshi, Inouye, Takaya, Morimoto, Keisuke, Fukuyama, Takahide, Ryu, Ilhyong
• Format: Article
• Language: English
• Subjects: Alcohol; Alkenes; carbon monoxide; carbonylation; Carbonyls; Carboxylic acids; Catalysts; Chemistry; Esters; Iodides; multicomponent reactions; Palladium; radical reactions; Radicals
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201200752

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 [Pd2(CNMe)6][PF6]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. Light, camera, ATCion: Atom‐transfer carbonylation of alkyl iodides to afford carboxylic acid esters was accelerated by the addition of transition‐metal catalysts under photoirradiation. The carbonylation step proceeded through a radical mechanism.