| |
[摘要]：L2Pd(0) and L2Pd(II) complexes, where L=t-Bu-2(p-NMe2C6H4)P, have been identified as efficient catalyst systems for the Heck alkynylation of a variety of aryl bromides (17 examples) and aryl/heteroaryl chlorides (31 examples) with a range of aryl- and alkyl-acetylenes in excellent yields, under relatively low Pd loadings. The single-crystal X-ray structure determination of the presumably active catalytic species, L2Pd(0), was carried out in this study to better understand the superior activity of the current catalyst system from a structure activity relationship point of view. The P-Pd-P bond angle indicates that the complex is bent (174.7 degrees) in comparison to the perfectly linear (180.0 degrees) structure of the analogous Pd(t-Bu3P)(2). Preliminary mechanistic studies on the negative copper effect and substrate effect of aryl acetylenes were conducted to better understand the cross-coupling pathway of Heck alkynylation. |
|
