Development and mechanistic investigation of the palladium-catalyzed α-arylation of aldehydes and N-arylation of ammonia

cross-coupling;palladium;homogeneous catalysis;ammonia;aldehydes;arylation;amination

Vo, Giang D.

关键词: cross-coupling;    palladium;    homogeneous catalysis;    ammonia;    aldehydes;    arylation;    amination;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/18494/Vo_Giang.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

A general method for the palladium-catalyzed α-arylation of aldehydes was developed to couple linear and branched aldehydes with electron-poor and electron-rich bromo- and chloroarenes in high yields. Catalysts generated from allylpalladium chloride (APC) and 1,1’-diphenylphosphinoferrocene (DPPF) coupled linear aldehydes with aryl bromides, and catalysts generated from APC and Q-phos coupled branched aldehydes with aryl bromides and chlorides. Arylpalladium enolate complexes of aldehydes were proposed as intermediates in this process, and these complexes were isolated and characterized. The effects of steric and electronic properties of the aryl groups on the rates of reductive elimination and yields of coupled products were evaluated. The reactivity of these complexes and an arylpalladium enolate complex of acetone was compared. A general method for the palladium-catalyzed coupling of ammonia with aryl halides and sulfonates was also developed. The catalyst generated from Pd[P(o-tol)3]2 and the alkylbisphophine CyPF-t-Bu is a highly active and selective catalyst for the coupling of ammonia with aryl chlorides, bromides, iodides, and sulfonates. The couplings of ammonia with this catalyst conducted with a solution of ammonia in dioxane formed primary arylamines from a variety of aryl electrophiles in high yields. Catalyst loadings as low as 0.1 mol % were sufficient for reactions of many aryl chlorides and bromides. In the presence of this catalyst, aryl sulfonates also coupled with ammonia for the first time in high yields. The utility of this method to generate amides, imides, and carbamates is illustrated by a one-pot synthesis of a small library of these carbonyl compounds from aryl bromides and chlorides, ammonia, and acid chlorides or anhydrides. Mechanistic studies showed that reactions conducted with the combination of CyPF-t-Bu and Pd[P(o-tol)3]2 as catalyst occur with faster rates and higher yields than those conducted with CyPF-t-Bu and palladiun(II) as catalyst precursors.