From Solution-Phase to Solid-Phase Enyne Metathesis: Crossover in the Relative Performance of Two Commonly Used Ruthenium Pre-Catalysts
作者:Dominic E. A. Brittain、B. Lawrence Gray、Stuart L. Schreiber
DOI:10.1002/chem.200500279
日期:2005.8.19
A crossover in the ability of two distinct ruthenium-based metathesis pre-catalysts to effect the synthesis of dialkenylboronic esters in solution and on the solid-phase was observed. Specifically, while the Grubbs 2nd generation pre-catalyst 3 affords a greater degree of conversion to product than the Hoveyda-Grubbs pre-catalyst 2 in a solution-phase enyne-metathesis reaction, this trend is reversed
观察到两种不同的钌基复分解前催化剂在溶液中和在固相上影响二烯基硼酸酯合成的能力的交叉。具体地,尽管在溶液相烯炔复分解反应中,格鲁布斯第二代预催化剂3提供比霍维达格鲁布斯预催化剂2更大的产物转化率,但是在固相变体中这种趋势是相反的。系统研究表明,这种趋势是普遍的,而与反应中均烯丙基醇和炔基硼酸酯组分的变化以及所用固体载体的类型无关。确定这种趋势的机理假说的实验强调了钌在易位重排后仍与底物结合的重要性,并发现膦配体的存在对固相反应的成功有害。因此,这些结果表明,不含膦的预催化剂(例如2)在具有挑战性的固相复分解反应中具有扩展的作用。