Pd/light-accelerated atom-transfer carbonylation of alkyl iodides: applications in multicomponent coupling processes leading to functionalized carboxylic acid derivatives.

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.

Synthesis of alkyl alkynyl ketones by Pd/light-induced three-component coupling reactions of iodoalkanes, CO, and 1-alkynes.

Under photoirradiation conditions using xenon light, in the presence of a catalytic amount of PdCl(2)(PPh(3))(2) with triethylamine as a base, a three-component coupling reaction of iodoalkanes, carbon monoxide, and terminal alkynes proceeded to give alkyl alkynyl ketones in good yields.

Effective acceleration of atom transfer carbonylation of alkyl iodides by metal complexes. Application to the synthesis of the hinokinin precursor and dihydrocapsaicin.

[reaction: see text] Atom transfer carbonylation (ATC) of alkyl iodides leading to carboxylic acid esters is effectively accelerated by Pd(PPh(3))(4) and Mn(2)(CO)(10) under photoirradiation conditions. In the presence of amines, Pd(0) complexes affected double carbonylations leading to alpha-keto amides, whereas Mn(2)(CO)(10) accelerated only a single carbonylation reaction leading to the corresponding amides. The Pd(0)-accelerated ATC system was successfully applied to the synthesis of hinokinin and dihydrocapsaicin.

A copper-free Sonogashira coupling reaction in ionic liquids and its application to a microflow system for efficient catalyst recycling.

[reaction: see text] The PdCl2(PPh3)2-catalyzed Sonogashira coupling reaction, in good to high yields, was performed in an ionic liquid ([BMIm][PF6]) in the absence of a copper salt. The use of an ionic liquid allows for the facile separation and recycling of the catalyst. The application of the above reaction in a microflow system in conjunction with an IMM micromixer was also successful.

Cascade radical reactions catalyzed by a Pd/light system: cyclizative multiple carbonylation of 4-alkenyl iodides.

Cascade reactions of 4-alkenyl iodides, involving a carbonylation-cyclization-carbonylation sequence, were accomplished by a hnu/Pd system. The stereochemical outcomes suggest that radical carbonylation and subsequent acyl radical cyclization may be involved in this reaction.