作者:Irene C. Christoforou、Panayiotis A. Koutentis
DOI:10.1039/b702154b
日期:——
The regiocontrolled preparation of triarylisothiazoles is presented. 3-Halo-5-phenylisothiazole-4-carbonitriles, 1 (hal = Cl) and 18 (hal = I), are converted into the corresponding 4-bromo derivatives 5 (3-hal = Cl) and 24 (3-hal = I) via a Hunsdiecker strategy while the 4-iodo analogues 7 (3-hal = Cl) and 22 (3-hal = I) are prepared via a Hoffmann and Sandmeyer strategy. Regioselective Suzuki, Stille and Negishi reactions occur at C-4 with both the 4-bromo- and 4-iodoisothiazoles 5 and 7, the latter being more reactive than the former. 3-Iodoisothiazoles 22 and 24 fail to give regiocontrolled Suzuki, Stille or Negishi couplings, however, 4-bromo-3-iodo-5-phenylisothiazole24 gives the regiospecific palladium catalysed Ullmann-type reaction product 3,3â²-bi(4-bromo-5-phenylisothiazole)25. Alkali hydrolysis of 3-chloro-4,5-diphenylisothiazole8 gives the 3-hydroxy analogue 12 which is converted into 3-bromo-4,5-diphenylisothiazole13 with POBr3. 3-Bromoisothiazole13 reacts with phenylzinc chloride to give 3,4,5-triphenylisothiazole17 but fails to undergo effective Suzuki or Stille couplings. 3,5-Diphenylisothiazole-4-carbonitrile26 is converted into the 4-bromo- and 4-iodo-3,5-diphenylisothiazoles 30 and 34 both of which are effective for Suzuki and Stille couplings. A series of triarylisothiazoles are prepared in this manner and fully characterised.
本文介绍了三芳基异噻唑的区域控制制备方法。3-卤-5-苯基异噻唑-4-氰化物(1(卤=Cl)和18(卤=I))通过Hunsdiecker策略转化为相应的4-溴衍生物(5(3-卤=Cl)和24(3-卤=I)),而4-碘类似物(7(3-卤=Cl)和22(3-卤=I))则通过Hoffmann和Sandmeyer策略制备。区域选择性的Suzuki、Stille和Negishi反应在C-4位进行,无论是4-溴还是4-碘异噻唑(5和7),后者比前者更具反应活性。然而,3-碘异噻唑(22和24)未能给出区域控制的Suzuki、Stille或Negishi耦合反应,但4-溴-3-碘-5-苯基异噻唑24给出了区域特异性的钯催化Ullmann型反应产物3,3′-双(4-溴-5-苯基异噻唑)25。3-氯-4,5-二苯基异噻唑8的碱水解得到3-羟基类似物12,该物质与POBr3反应转化为3-溴-4,5-二苯基异噻唑13。3-溴异噻唑13与苯基锌氯反应得到3,4,5-三苯基异噻唑17,但未能进行有效的Suzuki或Stille耦合反应。3,5-二苯基异噻唑-4-氰化物26转化为4-溴和4-碘-3,5-二苯基异噻唑30和34,两者均能有效进行Suzuki和Stille耦合反应。通过这种方法制备了一系列三芳基异噻唑并进行了完全表征。