Boronate Titanium Alkylidene Reagents for Diversity-Based Synthesis of Benzofurans
作者:Gordon J. McKiernan、Richard C. Hartley
DOI:10.1021/ol035677g
日期:2003.11.1
[reaction: see text] Novel titanium benzylidenes (Schrock carbenes) bearing an arylboronate group are generated from thioacetals with low valent titanium species, Cp(2)Ti[P(OEt)(3)](2), and alkylidenate Merrifield resin-bound esters to give enol ethers. Treatment with 1% TFA gives 2-substituted (benzo[b]furan-5-yl)boronates, and solid-phase Suzuki cross-coupling gives 2,5-disubstituted benzofurans
[反应:请参阅文字]带有芳基硼酸酯基团的新型钛亚苄基化合物(Schrock carbenes)是由具有低价钛类的硫缩醛,Cp(2)Ti [P(OEt)(3)](2)和烷基化的Merrifield树脂制得的,结合酯得到烯醇醚。用1%TFA处理得到2-取代的(苯并[b]呋喃-5-基)硼酸酯,并且固相Suzuki交叉偶联得到2,5-二取代的苯并呋喃。硫缩醛底物的合成步骤包括选择性锂化-硼化,MOM基团的水解而不影响硼酸酯,以及与双(频哪醇)二硼的交叉偶联。