Catalytic chemodivergent annulations between α-diketones and alkynyl α-diketones

Four types of unprecedented and chemodivergent reactions between α-diketones and alkynyl α-diketones have been achieved under the catalysis of phosphine and Br?nsted base, respectively, leading to the rapid construction of four different classes of biologically important but synthetically challenging molecular scaffolds including 2-hydroxyfuran-3(2H)-ones, 4-hydroxy-2-oxabicyclo[2.2.1]heptan-3-ones, 1,3-diaryl cyclobutanes, and 4-(furan-2(3H)-ylidene)cyclopent-2-enones. The formation of the products includes two novel rearrangement processes, and further transformations on the products can be easily achieved to deliver value-added substances such as highly functionalized cyclopentanes. Moreover, the 2-hydroxyfuran-3(2H)-one products display promising photophysical properties such as green luminescence under UV light and aggregation-induced emission effect,showing the practical application value of this work. The great potential of α-diketones in both synthetic chemistry and material science has been unambiguously demonstrated.     

Theoretical Study on Enol-keto Tautomerism of α-Fluorine-β-diketones

1 INTRODUCTION β-diketones are a class of high functional com- pounds with outstanding optical, electric and magne- tic properties[1], and the negative ion may act as an excellent chelating agent. Hall[2] have studied β-di- ketone/metal ion complexes and indicated that the ability of combination correlates with the keto-enol distribution in solution. The enol-keto equilibrium existing in β-diketones has been extensively studied over several decades[3~9]. Burdett[10] have investiga- ted…     

A mild,simple and efficient method for selectiveα-monobromination of 1,3-diketones and β-ketoesters using pyridinium bromochromate

Pyridinium bromochromate has been found to be a highly efficient and selective reagent for theα-monobromination of 1,3-diketones andβ-keto-esters in the absence of base,Lewis acid,or other catalyst.The products were formed in high to excellent yields under mild reaction conditions and in short reaction times.     

Reactions of enamines with fluorinated acyl chlorides----Synthesis of fluorinated 1,3-diketones and 1,3-keto-aldehydes

The reactions of enamines (1a-b,4,6) with fluorinated acyl chlorides (2a-d) produced fluorinated 1,3-diketones (3a-f) and 1,3-keto-aldehydes (7a-c) in good yields as well as byproducts fluorinated acylamides (5a-c).It is proposed that the reactions involve nucleophilic attack by the C-atora and/or N-atom of the enamines on acyl carbon of the fluorinated acyl chlorides.     

A practical synthesis of α-bromo/iodo/chloroketones from olefins under visible-light irradiation conditions

A practical synthesis of α-bromo/iodo/chloroketones from olefins under visible-light irradiation conditions has been developed.In the presence of PhI(OAc)₂ as promoter and under ambient conditions,the reactions of styrenes and triiodomethane undergo the transformation smoothly to deliver the corresponding a-iodoketones without additional photocatalyst in good yields under sunlight irradiation.Mea nwhile,the reactions of styrenes with tribromomethane and trichloromethane generate the desiredα-bromoketones and a-chloroketones in high yields by using Ru(bpy)₃Cl₂ as a photocatalyst under blue LED(450-455 nm) irradiation.     

Three-component reaction of alkyl isocyanides with acetylenic esters and pyridine-2-carboxaldoxime or α-furildioxime:Synthesis and dynamic NMR study of ketenimines and bis(ketenimines)

The addition of pyridine-2-carboxaldoxime or α-furildioxime to dialkyl acety lenedicarboxy lates under neutral conditions in the presence of alkyl isocyanides leads to ketenimines and bis(ketenimines) in good yields.     

Bismuth Mediated Organic Reaction: A Convenient Method for the Synthesis of Allylic (Benzylic) Selenides and α-Organylselenocarbonyl Compounds in Aqueous Media

Organic reactions promoted by active metals have aroused much interest in recent years. Active bismuth has been used in Barbier-type reaction of allylic halides with aldehydes1 and aldimines2 as well as Reformatzky type reaction3. Other publications referred to the cross coupling between aldehydes and α-diketones4, the substitution to benzotriazole drivatives5 and the reductive coupling reaction of nitro compounds6. These reactions generally promoted by elemental bismuth generated in situ fr…     

TRIPLICATED α-GLOBIN GENE LOCI IN A CHINESE FAMILY

Utilizing restriction endonuclease mapping and blot bybridization, we have determined the arrangement of the α-globin genes in a Chinese family. The father and mother had no obvious α-thalassemia symptoms, but their twin daughters suffered from HbH disease. The gene analysis showed that the mother had three α-globin genes in one chromosome and no α-globin gene in the other (ααα/--), the father was a heterozygote of α-thal2 (αα/-α). Their twin daughters were double heterozygotes of α-thall and the rightward deletion genotype α-thal2 (--/-α)     

Synthesis of α-Bromine- Terminated Polystyrene Macroinitiator and Its Initiation of MMA Polymerization by ATRP

In the present paper the synthesis of block copolymers via the transformation from living anionic polymerization (LAP) to atom transfer radical polymerization (ATRP) was described. Α-Bromine-terminated polystyrenes(PStBr) in the LAP step was prepared by using n-BuLi as initiator, tetrahydrofuran (THF) as the activator, α-methylstyrene (α-MeSt) as the capping group and liquid bromine (Br2) as the bromating agent. The effects of reaction conditions such as the amounts of α-MeSt, THF, and Br2 as well as molecular weight of polystyrene on the bromating efficiency (BE) and coupling extent (CE) were examined. The present results show that the yield of PStBr obtained was more than 93.8% and the coupling reaction was substantially absent. PStBr was further used as the macroinitiator in the polymerization of methyl-methacrylate(MMA) in the presence of copper(Ⅰ) halogen and 2,2-bipyridine(bpy) complexes. It was found that the molecular weight of the resulted PSt-b-PMMA increased linearly with the increase of the conversion of MMA and the polydispersity was 1.2-1.6. The structures of PStBr and P(St-b-MMA) were characterized by 1H NMR spectra.     

溴化镁催化的1,2,3,4-四氢吡啶酮无溶剂合成研究

An efficient and environmentally friendly procedure for the one-pot synthesis of tetrahydropyrimidinones from aldehydes, β-diketones and urea/thiourea by using magnesium bromide as an inexpensive and easily available catalyst under solvent-free conditions was described. Compared with the classical Biginelli reaction conditions, this new method has the advantage of good to excellent yields (74%-94%) and short reaction time (45-90 min). The structure of the Biginelli reaction product from β-diketone, salicylaldehyde and urea has been proposed to possess an oxygen-bridge by cyclization (intramolecular Michael-addition).     

A NOVEL METHOD FOR SYNTHESIZING α,α-DISUBSTITUTED α-AMINO ACID——DIALKYLATION OF 2-OXAZOLIN-5-ONE

4,4-Dialkyl-2-oxazolin-5-ones are prepared by one step reaction of 2-oxazolin-5-one with themagnesium methyl carbonate(MMC)and alkyIhalides.It is a novel and convenient method for synthesis of α,Υ-disubstitutcd α-amino acid by hydrolysis of 4,4-dialkyl-2-oxazolin-5-ones.     

Hydrothermal and Solvothermal Synthesis of the Complex Fluoride α′-SrAIF5

The complex fluoride α′-SrAlF5 has been synthesized through hydrothermal and solvothermal methods under mild conditions.The effects of the molar ratio of starting materials,temperature,reaction time and solvents on the synthesis of α′-SrAlF5 were discussed.The final products were characterized by XRD and SEM.The rod-like shape of α′-SrAlF5 is shown in SEM images.     

Solvent-free synthesis of substituted thiopyrans via multicomponent reactions of α-haloketones

A straightforward and efficient method for the synthesis of thiopyran derivatives via three-component reaction of alkyl propiolate, benzoylisothiocyanate or its derivatives and α-haloketones in the presence of triphenylphosphine under solvent-free conditions at 70℃ without using any catalyst is reported, The method offers several advantages including high yields of products and an easy work-up procedure.     

Ligand Steric Effects on Naphthyl-α-diimine Nickel Catalyzed α-Olefin Polymerization

Naphthyl-α-diimine nickel complexes with systematically varied ligand sterics, activated by modified methylaluminoxane(MMAO), were tested in the polymerization of higher α-olefin(1-hexene, 1-decene and 1-hexadecene) under suitable conditions. The polymerization results indicated the possibility of precise microstructure control, depending on catalyst structure, polymerization temperature, monomer concentration and types of monomers, which in turn strongly affects the resultant polymer properties. Naphthyl-α-diimine nickel complex bearing chiral bulky sec-phenethyl groups in the o-naphthyl position showed good catalytic activity, and resulted in branched polymers(42-88/1000 C) with high molecular weights(M_n:(4.3-15.2) × 10~4 g·mol~(-1)) and narrow molecular weight distribution(M_w/M_n = 1.13-1.29, RT), which suggested a living polymerization. The increasing steric hindrance of catalyst leads to enhance insertion for 2,1-insertion of α-olefin and the chain-walking reaction.     

A NEW SYNTHETIC ROUTE TO α-DAMASOONE

A new synthetic route to α—damascone (4) starting from citral is described-The synthesis features allylatioa of α—cyclocitral (1) with allylic bromide in the presence of tin powder to give the crucial intermediate 1—(2',6',6'—trimethylcyclo— hexen —2'—yl)—3—buten —1—ol(2a) and (2b) in a combined yield of 70%.     

Synthesis of Diphenyl α-（Dipropoxyphosphoramido）alkyl-phosphonates

A convenient method has been developed for the synthesis of diphenyl α-（dipropoxyphosphoramido）alkyl- phosphonates under mild conditions, namely the reaction of dipropyl phosphoramidate （1） with a para（un）substituted benzaldehyde or cyclicketone （2） and triphenyl phosphite （3） by a one-pot procedure with the aid of acetyl chloride.     

Studies on Fragrance Raw Materials of α-Terpineol Analogues

Thirty four α-substituted or α, α-disubstituted-( 1-methylcyclohexen-4-yl )methanols and α-substituted or α,α-disubstituted-(4-methylcyclohexyl) methanols weresynthesized. Thirty two of them are new compounds. 1H NMR and IR spectra of allthe compounds were determined, MS spectra of some of them were obtained as well.The characteristic odors were evaluated.Keywords Fragrance raw materials,α-Terpineol analogues, Synthesis, Structuredetermination     

SYNTHESIS AND STRUCTURE OF α''''-ACE-TYL-α-THIENYL PHENYLACETYLENEDI-COBALT HEXACARBONYL AND α''''-ACE-TYL-α-THIENYL P-ACETYLPHENYLACE-TYLENEDICOBALT HEXACARBONYL

Friedel-Crafts acylation of α-thienyl phenylacetylenedicobalt hexacarbonyl with acetyl chlo-ride has been investigated. The results showed thiophene nucleus to be somewhat more reactivein the electrophilic acylation than benzene nucleus and benzene nucleus in turn to be morereactive than acylated thiophene nucleus. Through the acylation two new cobalt- carbon clustercomplexes, i. e. α'-acetyl-α -thienyl phenylacetylenedicobalt hexacarbonyl Ⅰ and α'- acetyl-α-thienyl P- acetylphenylacetylenedicobalt hexacarbonyl Ⅱ, were synthesized. The single crystalstructure of Ⅱ was determined as well as the structures of Ⅰ and Ⅱ were elucidated in termsof combustion analysis, IR and ~1HNMR spectroscopy. The crystal structure of Ⅱ belongsto the monoclinic system, space group Pz_1/n; cell parameters a = 8 .037(2), b = 16 .347(3),c = 17.823(2)A, β= 102.68(2)°, D_c = 1.61g·cm~(-3), Z = 4, and the final factor R = 0.040.     

Preparation and Application of Perchloric Acid Supported on Alumina (Al2O3-HClO4) to the Synthesis of α-(α-Amidobenzyl)-β-naphthols

Preparation of perchloric acid supported on alumina and its primary application as a solid supported heterogeneous catalyst to the synthesis of α-(α-amidobenzyl)-β-naphthols by a one-pot, three-component condensation of benzaldehydes, β-naphthol and acetamide or benzamide under thermal solvent-free conditions were described. The present methodology offers several advantages such as simple procedure, shorter reaction time, and excellent yields.     

Sm／BiCl3 System Mediated Reformatsky Type Reactions of α—Bromoacetophenone with Aldehydes in THF—H2O Solvent

In the presence of samarium-bismuth(Ⅲ） chloride,intermolecular aldol type reations of α-bromoacetophenone with various aldehydes in tetrahydrofuran-water mixed solvent afford β-hydroxy ketones in moderate to good yields under mild and neutral conditions.