Ligand-less palladium-catalyzed direct 5-arylation of thiophenes at low catalyst loadings
作者:Julien Roger、Franc Požgan、Henri Doucet
DOI:10.1039/b819912d
日期:——
Ligand-less Pd(OAc)2 provides a very efficient catalyst for the direct5-arylation of thiophenederivatives. With this catalyst, a low palladium concentration (0.1–0.001 mol%) should be employed in order to obtain high yields of coupling products. At higher concentrations a fast formation of inactive “Pd black” generally occurs. Substrates/catalysts ratios up to 100000 can be employed with the most
Palladium associated with cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane (Tedicyp) was found to promote the direct 2-arylation of a variety of thiophene derivatives via CH functionalisation in good yields using very lowcatalystloadings. Electron-deficient, electron-excessive or sterically-congested aryl bromides are tolerated. Moreover, several substituents on the aryl bromide
of an air‐stable, robust palladium/tridentate phosphane catalyst in direct CH and CCl activation reactions is reported (see scheme; DMAc=N,N‐dimethylacetamide, TBAB=tetra‐n‐butylammonium bromide). Electron‐rich, electron‐poor, and polysubstituted furans (X=O), thiophenes (X=S), pyrroles (X=NR5), and thiazoles were arylated with chloroarenes in the presence of the catalyst.
穿上它的环:在直接C中的使用对空气稳定的,坚固的钯/三齿磷烷催化剂 H和13 C 氯活化反应报道(参见方案;的DMAc = Ñ,Ñ二甲基乙酰胺,TBAB =四Ñ -丁基溴化铵)。在催化剂存在下,富电子,贫电子和多取代的呋喃(X = O),噻吩(X = S),吡咯(X = NR 5)和噻唑被氯芳烃芳基化。