Research On HBF₄·SiO₂-catalyzed The Enamination Of β-dicarbonyl Compounds, And NiCl₂(dppp) Catalyzed Suzuki-Miyaura Coupling

In chapter 2:Enamination ofβ-dicarbonyl compounds formingβ-enaminones andβ-enamino esters, is an important and widely used transformation in organic chemistry.They are an important class of synthetic intermediates for the preparation of various heterocyclic and biologically active compounds such as dopamine auto-receptor agonists, acetylcholinestersase inhibitors, oxytocin antagonists and anticonvulsants. The most well-known route toβ-enaminones involves the direct condensation ofβ-dicarbonyl compounds with amines in an aromatic solvent with azetropic removal of water.3 Several other improved methods using catalysts such as Al2O34a, SiO2/microwaves4b, montmorillonite K-104c, NaAuClO44d, Bi(TFA)34e, Zn(ClO4)2-6H2O4f, CeCl3·7H2O4g, HClO4-SiO24h, ZrOCl2-8H2O4i and Sc(OTf)34j. for the preparation of P-enaminones andβ-enamino esters have been reported. However, these methods suffer from one or more drawbacks such as the use of expensive or less readily available reagents, vigorous reaction conditions, longer reaction times and unsatisfactory yields. Due to the importance of P-enamino compounds in organic synthesis, the development of facile and efficient synthetic methods to synthesize these compounds under mild reaction conditions is still desirable. Herein, we report a mild, efficient and recyclable catalyst HBF4-SiO2(fluoroboric acid was supported on SiO2) catalyzed the chemoselective enamination ofβ-dicarbonyl compounds under solvent-free conditions to produce theβ-enaminones and P-enamino esters in excellent yields.To the best of our knowledge, there has been no report on the use of HBF4·SiO2 in synthesis ofβ-enaminones andβ-enamino esters.In chapter 3:1,2,4-oxadiazole is a very important class of heterocyclic small organic molecules compound and exists widely in a variety of natural products and pharmaceutical intermediates. So Synthesis on their structure has been reported more. At the same time, there is few about the N,N-dialkyl-3-phenyl-1,2,4-oxadiazole. We think looking for convenient, fast method for the synthesis of these compounds is necessary. TMC is widely used in carbohydrate chemistry and peptide chemistry as Condensation reagent or dehydrating agent but few in synthesis of heterocyclic compound. In this paper, we attempt to synthesize 1,2,4-oxadiazole compounds as a substrate. First of all, we synthesize a series of amidoxime under base using nitrile and reacting them with TMC and getting satisfied result of N,N-dimethyl-3-phenyl-1,2,4-oxadiazol-5-amine. The procedure is convenient. So we afford a new rout to synthesize 1,2,4-oxadiazole compound.In chapter 4:We present a highly active,inexpensive, universally applicable, and markedly stable [1,3-bis(diphenylphosphino)propane]- nickel(Ⅱ) chloride [Ni(dppp)Cl2] catalyst that is capable of effecting the Suzuki-Miyaura cross-coupling of the inherently less reactive but readily available aryl tosylates and mesylates with only 1 mol% loading and in the absence of extra supporting ligand. Under the optimized reaction conditions, cross-coupling of a wide range of activated, non-activated, and deactivated,as well as sterically hindered and heteroaromatic substrates (36 examples) could proceed efficiently to afford the coupled products in 53-99% yields. Consequently, the results presented in this work provide a significant advance in Suzuki-Miyaura cross-coupling in terms of generality, practicality, and cost which are key concerns in recent research regarding transition metal-catalyzed cross-couplings.