Synthesis of 3-substituted furans by directed lithiation and palladium catalysed coupling
作者:David S. Ennis、Thomas L. Gilchrist
DOI:10.1016/s0040-4020(01)82041-x
日期:1990.1
The 5-position of the furan ring of 4,4-dimethyl-2-(2-furyl)oxazoline (1a) was protected by a trimethylsityl group. The product, compound (2a), was then lithiated at the 3-position with sec-butyllithium and converted to the bromozinc species (2d) with zinc bromide. Coupling reactions with a range cf aryl-, acyl-, and vinyl halides were performed with Pd(PPh3)4 as catalyst. The reaction with (l-bromoethenyl)-
4,3-二甲基-2-(2-呋喃基)恶唑啉(1a)的呋喃环的5位被三甲基苯乙烯基保护。然后将产物化合物(2a)在3位用仲丁基锂锂化,并用溴化锌转化为溴锌物质(2d)。以Pd(PPh3)4为催化剂,进行了卤代芳基,酰基和乙烯基卤的偶合反应。与(1-溴乙烯基)-三甲基硅烷的反应是异常的,因为它给出了两种产物(2l)和(2m)的混合物。异常产品的来源(2l)进行了讨论。该硅烷与2-噻吩基,2-呋喃基和苯基-锌锌的偶联反应也已经进行:在每种情况下,预期偶联产物和异构体的混合物-乙烯-2-基三甲基硅烷,获得了。显示产物的比例取决于进行偶联的温度。在噻吩环的3-位将4,4-二甲基-2-(2-噻吩基)恶唑啉(1b)锂化并偶联至碘苯而不保护5-位。