Heck反应机理及示例

Heck 反应的机理及示例

机理：Heck 反应的机理有一定的规律，通常认为反应共分四步：（a ）氧化加成（Oxidative addition ）: RX (R 为烯基或芳基，X=I > TfO > Br >> Cl)与Pd 0L 2的加成，形成Pd Ⅱ配合物中间体；（b ）配位插入 （Cordination-insertion ）:烯键插入Pd-R 键的过程； （c ）β-H 的消除； （d ）催化剂的再生：加碱催化使重新得到Pd 0L 2。

示

例：

OMe

O

MeO

N O

NCO 2Me OMe

N O

MeO

O

NCO 2Me

OMe

Pd(PPh ) , NEt (12eq)MeCN, 80℃, 10h

12

A stirred solution of 1 (98 mg, mmol), triethylmine mL, mmol) and catalytic tetrakis(triphenylphosphine)palladium(0) (ca. 5 mg, 4 μmol) in mL of acetonitrile was heated at 80 ℃ in a sealed tube under an argon atmosphere for 10 h. The reaction mixture turned dark orange after ca. 10 min, and the catalyst plated out on the walls of the tube as a shiny layer of palladium metal upon completion of the reaction. The reaction mixture was cooled to room temperature; the reaction was quenched with aqueous NaHCO 3(15 mL), and

the mixture was extracted with EtOAc (4×10 mL). The organic extracts were washed with

aqueous NaHSO

3 (1×15 mL), water (1×15 mL), and brine (1×15 mL) and dried over MgSO

4

.

Filtration, concentration, and purification of the orange residue by flash column chromatography (45:55 Et

2

O/hexanes) gave 66 mg (90%) of 19 as a colorless solid: mp 193-194 ℃; Rf = (8:2 Et2O/hexanes).