This paper reports the design and synthesis of a novel series of 8-arylpyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-amines via microwave-assisted multi-step synthesis. A common precursor of the whole series, 3-amino-5-bromothieno[2,3-b]pyridine-2-carbonitrile, was rapidly synthesized in one step from commercially-available 5-bromo-2-chloronicotinonitrile. Formylation with DMF-DMA led to (E)-N′-(5-bromo-2-cyanothieno[2,3-b]pyridin-3-yl)-N,N-dimethylformimidamide (4) which was conveniently functionalized at position 8 by palladium-catalyzed Suzuki-Miyaura cross-coupling to introduce a heteroaromatic ring. High-temperature formamide-mediated cyclization of the cyanoamidine intermediate gave seventeen 8-arylpyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-amines. The inhibitory potency of the final products was evaluated against five protein kinases (CDK5/p25, CK1δ/ε, GSK3α/β, DYRK1A and CLK1) and revealed that 8-(2,4-dichlorophenyl)pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-amine 1g specifically inhibits CK1δ/ε and CLK1 (220 and 88 nM, respectively) while its 7-(2,4-dichlorophenyl)pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-amine isomer 10 showed no activity on the panel of tested kinases. Molecular modelling of 10 and 1g in the ATP binding sites of CK1δ/ε and CLK1 showed that functionalization at position 7 of pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-amines is likely to induce a steric clash on the CK1δ/ε P-loop and thus a complete loss of inhibitory activity.

本文报道的新颖系列8 arylpyrido的设计和合成[3'，2'：4,5]噻吩并[3,2- d ]嘧啶-4-胺通过微波辅助的多步合成。从市场上可买到的5-溴-2-氯代烟腈一步一步合成了整个系列的通用前体3-氨基5-溴代噻吩并[2,3- b ]吡啶-2-甲腈。用DMF-DMA甲酰化可生成（E）-N' -（5-溴-2-氰基噻吩并[2,3 - b ]吡啶-3-基）-N，N-二甲基甲酰胺（4）通过钯催化的Suzuki-Miyaura交叉偶联方便地在8位官能化以引入杂芳族环。氰基am中间体的高温甲酰胺介导的环化反应产生了十七个8-芳基吡啶基[3'，2'：4,5]噻吩并[3,2 - d ]嘧啶-4-胺。评估了最终产物对五种蛋白激酶（CDK5 / p25，CK1δ/ε，GSK3α/β，DYRK1A和CLK1）的抑制力，并揭示了8-（2,4-二氯苯基）吡啶基[3'，2'： 4,5] thieno [3,2 - d ]嘧啶-4-胺1g特异性抑制CK1δ/ε和CLK1（分别为220和88 nM），而其7-（2,4-二氯苯基）吡啶[3'，2 ′：4,5] thieno [3,2- d ]嘧啶-4-胺异构体10在所测试的激酶组上没有显示活性。CK1δ/ε和CLK1的ATP结合位点的10和1g分子模型表明，吡啶并[3'，2'：4,5]噻吩并[3,2 - d ]嘧啶-4-胺的7位官能化为可能会在CK1δ/εP环上引发空间冲突，从而完全丧失抑制活性。