Multi-stage Reactions in One-pot using Inorganic Supported Reagents

我们研究了一锅中使用无机支撑试剂的两阶段反应，假设两种试剂在均相溶液中相互反应，通过将它们支撑在单独的无机载体上而使它们相互失活。两步合成应该是可能的，其中可溶性试剂(a)首先与一种载体试剂(Y)反应，产物(B)与第二种载体试剂(X)反应，得到所需的最终产物(C)。通常，2-氨基噻唑是由α-环酮与单取代硫脲缩合或α-硫氰酸酯羰基化合物与芳香族或脂肪族胺盐酸盐反应制备的。采用KSCN/SiO_2-RNH_3AcO/Al_2O_3负载试剂体系，建立了一锅法制备2-氨基噻唑的简便方法。α-Halo酮首先与KSCN/SiO_2反应生成α-硫氰酸酯，后者与RNH_3AcO/Al_2O_3反应生成最终产物2-氨基噻唑。以CuBr_2/Al_2O_3- naoh /Al_2O_3为载体体系，用-β-二酮和硫醇一锅法合成α-烷基硫代-β-二酮。β-二酮与CuBr_2/Al_2O_3反应生成α-溴-β-二酮，溴化物与硫醇在碱NaOH/Al_2O_3存在下反应生成α-烷基硫-β-二酮。

We have investigated two-stage reactions in one-pot using inorganic supported reagents on the assumption that two reagents reacting each other in homogenous solution are rendered mutually inactive by supporting them onto separate inorganic supports. It should be possible that two-step synthesis, in which a soluble reagent (A) react first with one supported reagent (Y) and the product (B) with the second supported reagent (X) to give the desired final product (C). Typically, 2-aminothiazoles are prepared either by the condensation of α-halo ketones with monosubstituted thioureas or by the reaction of α-thiocyanato carbonyl compounds with aromatic or aliphatic amine hydrochlorides. We have developed a convenient method for the preparation of 2-aminothiazoles in one-pot from readily available α-halo ketones using supported reagents system KSCN/SiO_2-RNH_3AcO/Al_2O_3. α-Halo ketones react first with KSCN/SiO_2 affording α-thiocyanates, the latter moving to RNH_3AcO/Al_2O_3 and reactins with it to give the end product 2-aminothiazoles. We have also developed one-pot synthesis of α-alkylthio-β-diketones from-β-diketones and thiols using supported reagents system CuBr_2/Al_2O_3-NaOH/Al_2O_3. β-Diketones react with CuBr_2/Al_2O_3 to give α-bromo-β-diketones, and then the bromides react with thiols in the presence of the base NaOH/Al_2O_3 to afford the end product α-alkylthio-β-diketones.