Preparation of new pyrido[3,4-b]thienopyrroles and pyrido[4,3-e]thienopyridazines
- 作者：Vegar Stockmann ; Anne Fiksdahl
- 关键词：Pyrido[3 ; 4-b]thieno[2 ; 3-d]pyrrole ; Pyrido[3 ; 4-b]thieno[3 ; 2-d]pyrrole ; Pyrido[4 ; 3-e]thieno[2 ; 3-c]pyridazine ; Pyrido[4 ; 3-e]thieno[3 ; 2-c]pyridazine ; Suzuki cross coupling ; Diazotization ; Diazocoupling
- 刊名：Tetrahedron
- 出版年：2008
- 期刊代码：107_00404020
- 类别：ch
- 出版时间：4 August 2008
- 卷：64
- 期：32
- 页码：7626-7632
- 文件大小：358 K
摘要
Two new types of pyrido-fused tris-heterocycles (1a,b and 2a,b) have been prepared from 3-aminopyridine in five/six steps. A synthetic strategy for the preparation of the novel pyrido[3,4-b]thieno[2,3- and 3,2-d]pyrroles (1a,b) and pyrido[4,3-e]thieno[2,3- and 3,2-c]pyridazines (2a,b) has been studied. The Suzuki cross coupling of the appropriate 2- and 3-thienoboronic acids (3,4) and 4-bromo-3-pyridylpivaloylamide (9) afforded the biaryl coupling products (10,11) in high yields (85%). Diazotization of the hydrolysed (2-thienyl)-coupling product (12) and azide substitution gave the 3-azido-4-(2-thienyl)pyridine intermediate (72%, 14). 3-Azido-4-(3-thienyl)pyridine (15) was prepared by exchanging the previous order of reactions. The desired β-carboline thiophene analogues (1a,b) were obtained via the nitrene by thermal decomposition of the azido precursors (14,15). By optimising conditions for intramolecular diazocoupling, the corresponding pyridazine products (72–83%, 2a,b) were afforded.