2,3-Dibromobenzofuran (1) and 2,3,5-tribromobenzofuran (2) undergo regioselective Sonogashira- and Negishi-type cross-coupling reactions at the 2-position. Subsequent substitution reactions at C-3 are possible for the cross-coupling products obtained from compound 1. A regioselective functionalization of the 3,5-dibromobenzofurans derived from substrate 2 was achieved by an halogen-metal exchange which occurred selectively at the 3-position. In a conclusive reaction step cross-coupling reactions at C-5 were used to build up 2,3,5-trisubstituted benzofurans. As an example, the synthesis of eupomatenoid-15 (8) is described.
2,3-二溴苯并呋喃(1)和2,3,5-三
溴苯并呋喃(2)在2-位点进行区域选择性的Sonogashira型和Negishi型交叉偶联反应。从化合物1得到的交叉偶联产物在C-3位可以进行后续取代反应。通过对2来自底物2的
3,5-二溴苯并呋喃进行区域选择性功能化,实现了在3-位点选择性发生卤素-
金属交换。在最终的反应步骤中,利用C-5位的交叉偶联反应构建了2,3,5-三取代的
苯并呋喃。作为一个例子,描述了eupomatenoid-15(8)的合成。