The Study On The Synthesis Of Meldrum's Acid Derivatives In One-pot Multicomponent Reaction

Meldrum's acid is an exceedingly versatile reagent in organic synthesis.Thus,a wide array of synthetic transformations has emerged to synthesize the organic compounds of potential pharmacological activities using Meldrum's acid as the starting substrate.In this dissertation,the design of green methods which employing Meldrum's acid as an attractive material to prepare y-aminobutyric acid precursors,(3-substituted indole and their derivatives by one-pot three-component reaction were described.The main contents and contributions are listed as follows:1.The applications of Meldrum's acid in organic synthesis in recent years are briefly summarized.2.A triethylamine catalyzed three-component one-pot tandem reaction of aldehy des,Meldrum's acid and nitroalkanes was established to synthesize ?-nitrocarbonyl compounds under solvent-free conditions.This strategy provides an easy alternative synthetic approach to the useful intennediate y-nitrocarbonyl compounds with moder ate to good yields.All the compounds were characterized by 1H NMR,13C NMR,IR and HRMS.3.The synthesis of(3-substituted indoles derivitives.?1?.An efficient and facile procedure for the synthesis of 5-[?indol-3-yl?-arylmet hyl]-2,2-dimethyl-1,3-dioxane-4,6-dione derivatives has been developed by condensa tion of Meldrum's acid with aldehyde and indole in mixture solvent from H₂O and ethanol at room temperature using KH₂PO₄ as catalyst.The structures of products were detennined by ¹H NMR,¹³C NMR,IR and HRMS.The crystal structure of com pound L1-o was also confirmed by X-ray diffraction.This strategy can tolerate the diverse functional groups such as 4-methylbenzaldehyde and 4-methoxybenzaldeh yde and provides an alternative approach for easy access to the usefull synthetic inter mediate ?-indole derivatives in the yields of 48%?98%.?2?.The Yonemitsu condensation for the synthesis of ?-indole derivatives was developed successfully using Meldrum's acid,aldehyde and indole as the starting materials and little water as green promoter under melting condition.A series of 5-[?indole-3-yl?-arylmethyl]-2,2-dimethyl-1,3-dioxane-4,6-dione derivatives was synt hesized in 55%?94%yields.?3?.Ten kinds of ?-substituted indoles were prepared via the three-component one-pot reaction of aldehyde,indole and Meldrum's acid without catalyst.This study has the merits of using PEG-400 and water as the green solvent,catalyst-free,mild reaction conditions and moderate to good yields?72%?92%?.