Bandalla Siddarama Goud, Kerru Nagaraju, Thangalipalli Swathi, Dosarapu Vijaykumar, Mavurapu Satyanarayana, Jonnalagadda Sreekantha B, Vasam Chandra Sekhar
Department of Pharmaceutical Chemistry, Telangana University, Nizamabad 503322, India.
Department of Integrated Chemistry, Palamuru University, Mahbubnagar 509001, India.
ACS Omega. 2025 Jul 31;10(31):34442-34460. doi: 10.1021/acsomega.5c02665. eCollection 2025 Aug 12.
A cost-effective and eco-compatible 1CaO-1.5MgO binary metal oxide (BMO-1) served as an efficient solid-base catalyst in the Knoevenagel condensation (KC) reaction of a range of aldehydes with active methylene reagents (i) malononitrile and (ii) ethyl cyanoacetate in water at room temperature (RT) to produce α,β-unsaturated compounds in purity with a good -factor. We also report the ketone-malononitrile KC reaction and salicylaldehyde-malononitrile tandem KC-Michael addition effectively catalyzed by BMO-1. We report the synthesis of 31 α,β-unsaturated compounds that include 9 entirely new compounds under optimized conditions. We compared all catalyzed reactions with the "blank test" due to the high reactivity of active methylene reagents and emphasized the implication of the catalyzed aqueous KC reaction. We deduced the structure-activity relationship (SAR) between the catalyst and substrates, the plausible reaction mechanism, and the turnover frequency (TOF) data of the BMO-1 catalyst. For evaluation, we compared the efficiency of CaO, MgO, and 1.5CaO-1MgO (BMO-2), 1CaO-2MgO (BMO-3), and 1CaO-1MgO (BMO-4) catalysts in a model KC reaction. We prepared the MgO, CaO, BMO-1, and BMO-2 materials via an ultradiluted coprecipitation process and characterized the catalysts by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), CO temperature-programmed desorption (CO-TPD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques. The superior catalytic activity of BMO-1 is due to its high specific surface area of 97.6 m/g, surface basicity of 152.4 μmol/g, and smaller particle size of 16.9 nm compared to the other three materials. Catalyst recycling experiments indicate that BMO-1 was stable for up to five cycles for the KC reaction. The BMO-1 spent catalyst analysis indicated the fundamental reason for its deactivation. We also report the optimized conditions for a selected KC reaction for upscaling (100 mmol).
一种具有成本效益且与生态兼容的1CaO - 1.5MgO二元金属氧化物（BMO - 1）在一系列醛与活性亚甲基试剂（i）丙二腈和（ii）氰基乙酸乙酯于室温（RT）的水相中进行的Knoevenagel缩合（KC）反应中作为高效的固体碱催化剂，以高纯度和良好的产率生成α,β - 不饱和化合物。我们还报道了BMO - 1有效催化的酮 - 丙二腈KC反应以及水杨醛 - 丙二腈串联KC - 迈克尔加成反应。我们报道了在优化条件下31种α,β - 不饱和化合物的合成，其中包括9种全新的化合物。由于活性亚甲基试剂的高反应活性，我们将所有催化反应与“空白试验”进行了比较，并强调了催化水相KC反应的意义。我们推导了催化剂与底物之间的构效关系（SAR）、合理的反应机理以及BMO - 1催化剂的周转频率（TOF）数据。为了进行评估，我们在模型KC反应中比较了CaO、MgO以及1.5CaO - 1MgO（BMO - 2）、1CaO - 2MgO（BMO - 3）和1CaO - 1MgO（BMO - 4）催化剂的效率。我们通过超稀释共沉淀法制备了MgO、CaO、BMO - 1和BMO - 2材料，并通过X射线衍射（XRD）、布鲁诺尔 - 埃米特 - 泰勒（BET）、CO程序升温脱附（CO - TPD）、傅里叶变换红外（FT - IR）光谱、扫描电子显微镜（SEM）、能量色散X射线光谱（EDX）和透射电子显微镜（TEM）技术对催化剂进行了表征。BMO - 1的优异催化活性归因于其97.6 m²/g的高比表面积、152.4 μmol/g的表面碱度以及与其他三种材料相比16.9 nm的较小粒径。催化剂循环实验表明，BMO - 1在KC反应中稳定循环使用多达五次。对BMO - 1失活催化剂的分析揭示了其失活的根本原因。我们还报道了选定的KC反应放大至（100 mmol）规模的优化条件。
