Synthesis and biological evaluation of 1,2,4-trisubstituted imidazoles as inhibitors of transforming growth factor-β type I receptor (ALK5)

Guo, Changbin; Zhang, Chong; Li, Xingzhou; Li, Wei; Xu, Zhongliang; Bao, Liang-Liang; Ding, Yue; Wang, Lili; Li, Song

doi:10.1016/j.bmcl.2013.08.105

Cited by 12 publications

(1 citation statement)

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“…Imidazoles are key structures in biological systems and an active moiety in several drugs. [27][28][29][30] There are many approaches for the synthesis of substituted imidazoles. [31][32][33][34][35] However, these molecules are usually polar compounds; therefore, an increase in the surface hydrophobicity of the catalyst may lower the diffusibility and mass transfer into the mesochannels and, as a result, there needs to be a balance between hydrophobicity and polarity ( Figure 2).…”

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Increased SBA-15-SO3H Catalytic Activity through Hydrophilic/Hydrophobic Fluoroalkyl-Chained Alcohols (RFOH/SBA-15–Pr-SO3H)

Rostamnia

Doustkhah

2015

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A superior catalytic activity for the SBA-15-functionalized sulfonic acid containing fluoroalkyl chain alcohols (R F OH/SBA-15-Pr-SO 3 H adduct) is presented for the synthesis of highly substituted imidazoles. The advantages of this method include low catalyst loading, simple procedure, excellent yields, recyclability of catalyst, and short reaction times.Key words fluoroalkyl chain alcohols, TFE/SBA-15-Pr-SO 3 H, imidazole, multicomponent reaction Solid Brønsted acid catalysts have received a great deal of attention for applications in green and recyclable protocols and their versatility has been demonstrated in the various processes. 1-4 Mesoporous silica materials (MSM), such as SBA-15, offer high surface area, good thermal stability, and potential for tunability 5,6 by which it is possible to modify the surface activity and nature of of the MSM. 7-9 One approach is to functionalize with mercaptopropyltrialkoxysilane when a subsequent oxidation process provides a surface sulfonic acid functionality. 10,11 One of the major concerns in the area of sulfonated MSM is catalyst poisoning with water, and several groups have addressed this problem (Figure 1). 12-16 Karimi et al. developed an efficient catalytic system by immobilizing a hydrophobic ionic liquid onto SBA-15. 14,17 Co-functionalization of a hydrophobic functionality such as a phenyl group or alkyl chain with a Brønsted acid function is another approach to increase the hydrophobicity. 16,18 Unfortunately, this method results in pore-size restriction. Wilson et al. prepared a monolayer of MPTS which produced a highly functionalized SO 3 H inside the MSM-type material. 13 This method was efficient in the fabrication of highly acidic MSM-SO 3 H. To prevent pore-size decrease, phenylene-and ethylene-bridged periodic mesoporous organosilicas (PMO) have been investigated, 19,20 but these were most suitable for the hydrophobic compounds. Therefore, development of a MSM-SO 3 H catalyst resistant to poisoning by water while maintaining the suitable hydrophilicity remains a target. Figure 1 Silica/SO 3 H catalyst poisoning with waterFluorous compounds have the unusual property of being both hydrophobic and lipophilic and thus can cause an increase in the acid strength and decrease catalyst poisoning as a result of water-repellency of the surface. [21][22][23] We have demonstrated that confining fluoroalkyl-chain alcohols (R F OH) inside SBA-15 (R F OH/SBA-15) produces an efficient catalytic system by increasing mass transfer and water repellency. [24][25][26] and that such catalytic systems can be applied to the synthesis of 1,2,4,5-tetrasubstituted imidazoles by multicomponent reaction. Imidazoles are key structures in biological systems and an active moiety in several drugs. [27][28][29][30] There are many approaches for the synthesis of substituted imidazoles. 31-35 However, these molecules are usually polar compounds; therefore, an increase in the surface hydrophobicity of the catalyst may lower the diffusibility and mass transfer into the mesochannels and, as ...

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