Di(tert-butylperoxy)triphenylbismuth and the triphenylbismuth—tert-butyl hydroperoxide system as efficient oxidants of alcohols

Di(tert-butylperoxy)triphenylbismuth and the triphenylbismuth—tert-butyl hydroperoxide system react with aliphatic alcohols and cyclohexanol to give carbonyl compounds in high yields. The oxidation occurs as the radical dehydrogenation of alcohols; Bi derivatives serve as the sources of free radicals.     

Synthesis and reactivity of solid-supported organotrifluoroborates in Suzuki cross-coupling

Solid-supported organotrifluoroborates were prepared in high yields by ion exchange with Amberlyst resins. The reactivity of solid supported aryltrifluoroborates was evaluated in Suzuki-Miyaura couplings with numerous aryl bromide partners. Electron-rich and -poor substituents were tolerated on both substrates, providing yields up to 90%. Examples of alkyl-, alkenyl-, alkynyl-, and heteroaryltrifluoborates were also successfully cross-coupled to aryl halides.     

Organobismuth compounds : V. Preparation,characterization, and properties of triphenylbismuth diazide and dicyanide

Triphenylbismuth diazide and the dicyanide have been prepared and characterized. Previously reported triphenylbismuth hydroxide cyanide has been shown to be triphenylbismuth dicyanide. A trigonal bipyramidal structure is indicated for both the compounds on the basis of their infrared and laser Raman spectra. The molecular weight and conductance data for the diazide in acetone are also in accord with a molecular structure. The dicyanide is, however, decomposed in solution into diphenylbismuth cyanide and benzonitrile. Thermal decomposition of the solid dicyanide and the diazide has also been studied. The possibility of the conversion of the diazide and the dicyanide into the corresponding dicyanate has been explored. Unlike transition metal azides, the triphenylbismuth diazide does not react with CO. Triphenylbismuth dicyanide could also not be converted into the corresponding dicyanate by reaction with either HgO or MnO₂. Reaction with HgO afforded triphenylbismuth oxide and the reaction with MnO₂ gave uncharacterized products.     

First enantioselective synthesis of vinyl oxiranes from aldehydes and ylides generated from allyl halides and chiral sulfides

Asymmetric allylidenation of aldehydes with sulfur ylides is possible with proper substitution of the initial sulfide, to avoid the [2,3] sigmatropic rearrangement of the unsaturated ylides. One-pot reaction of (2R,5R)-dimethylthiolane with allyl halides, aldehydes, and sodium hydroxide in tert-butyl alcohol affords vinyl oxiranes in good yields. Enantiomeric excesses up to 90% and trans selectivities have been achieved with methallyl-type halides.     

Palladium-phosphinous acid-catalyzed cross-coupling of aryl and acyl halides with aryl-, alkyl-, and vinylzinc reagents

Several palladium-phosphinous acids have been prepared and employed in cross-coupling reactions of aryl or acyl halides with aliphatic and aromatic organozinc reagents. The POPd7-catalyzed reaction of aryl halides, including electron-rich aryl chlorides, and arylzinc reagents was found to afford biaryls exhibiting alkoxy, alkylthio, amino, ketone, cyano, nitro, ester, and heteroaryl groups in 75-93% yield. Excellent results were obtained with sterically hindered substrates which gave di- and tri -ortho-substituted biaryls in up to 92% yield. Aryl halides also undergo POPd7-catalyzed aryl-vinyl and aryl-alkyl bond formation under mild conditions. Styrenes and alkylarenes were prepared in 79-93% yield from aryl halides and vinyl or alkylzinc reagents. The replacement of aryl halides by acyl halides provides access to ketones which were produced in up to 98% yield when POPd was used as catalyst. This approach overcomes the limited substrate scope, reduced regiocontrol, and low functional group tolerance of traditional Friedel-Crafts acylation methods.     

Reaction of secondary and tertiary aliphatic halides with aromatic aldehydes mediated by chromium(II): a selective cross-coupling of alkyl and ketyl radicals

Takai-Utimoto reactions with secondary and tertiary aliphatic halides usually failed according to previous reports. Now, significant improvements could be achieved, and especially secondary aliphatic halides can be coupled to aromatic aldehydes in yields of up to >95%. A variety of processes are competing with the desired one, and thus conditions must be adapted to the nature of the aldehyde as well as the aliphatic halide used, as the outcome of these reactions is strongly affected by the putative radical intermediates.     

Quantitative Quaternization of Poly(4-Vinyl Pyridine)

Quaternization of poly(4-vinyl pyridine), (P4-VP) by common alkyl halides can be performed with relatively low (up to 65–70%) conversion yields. Here we describe fully quaternization of P(4-VP) with activated halides such as chloro 2-propanone and 2-chloroacetamide in dimethylformamide (DMF) at room temperature.     

Effective synthesis of benzyl halides triggered by in situ prepared hypervalent halides

An effective approach for the direct benzylhalogenation with in situ generation of hypervalent halides has been developed.A variety of benzyl halides are produced in moderate to excellent yields(up to 99%) with high regioselectivities.UV absorption spectrum is employed to detect the formation of ferr-butyl hypoiodite.     

Nickel-catalyzed asymmetric alpha-arylation of ketone enolates

An atropisomeric dipyridyldiphosphine, P-Phos, can effect highly enantioselective Ni-catalyzed alpha-arylation of ketone enolates with aryl halides to install an all-carbon quaternary stereogenic center in up to 98% ee and excellent yields.     

Synthesis and structure of triphenylbismuth bis(2-phenylaminobenzoate)

Interaction of triphenylbismuth with phenylanthranilic acid in the presence of hydrogen peroxide yields triphenylbismuth bis(2-phenylaminobenzoate), in which bismuth atoms have a distorted trigonal bipyramidal coordination with phenyl ligands in equatorial positions. The bond lengths (Å) are as follows: Bi-C, 2.193(5), 2.200(4), and 2.200(4); Bi-O, 2.252(4) and 2.300(4). Intramolecular hydrogen bonds N-H?O(=C) (H?O, 1.91, 1.97 Å; N?O, 2.634(9), 2.667(9) Å) and donor-acceptor interactions Bi?O(=C) (2.790(5) and 2.838(5) Å) exist in the molecule.     

Synthesis and Structure of Triphenylbismuth Difluoride

The reaction of triphenylbismuth dichloride with sodium fluoride in acetone leads to formation of triphenylbismuth difluoride in 73% yield. The X-ray diffraction data show that the bismuth atom in the two symmetrically independent molecules of bismuth difluoride has a trigonal-bipyramidal coordination with equatorial fluorine atoms. The Bi-F and Bi-C distances are 2.53(1)-2.59(1) and 2.10(3)-2.22(2) Å, respectively, and the FBiF angle is 175.1(5)°.     

Palladium-catalyzed highly regio- and stereoselective synthesis of (1E)- or (1Z)-1,2-dihalo-1,4-dienes via haloallylation of alkynyl halides

A highly efficient and selective synthesis of (1E)- or (1Z)-1,2-dihalo-1,4-dienes via Pd-catalyzed coupling of haloalkynes and allylic halides is described. The (1E)-1,2-dihalo-1,4-dienes were generated in good yields with excellent stereoselectivities (1E/1Z up to >98/2), while (1Z)-1,2-dihalo-1,4-dienes were produced in excellent yields and stereoselectivities (1Z/1E up to >98/2) by simply adding stoichiometric lithium halides.     

NHCs-mediated benzoates formation directly from aromatic aldehydes and alkyl halides

A NHCs-mediated benzoates formation was developed by treatment of aromatic aldehydes with alkyl halides in the presence of oxygen. Corresponding benzoate derivatives were obtained in high yields up to 99%. The reaction mechanism was also discussed and a NHCs-mediated O-alkylation and subsequent oxidation process was proposed.     

新型手性相转移催化剂的合成及其催化作用研究

以金鸡纳生物碱和2-氯甲基苯并咪唑为原料方便地合成了四种新型的手性相转移催化剂. 该类催化剂在相转移催化的二苯亚胺甘氨酸叔丁酯的对映选择性烷基化反应中, 可有效地催化多种卤代烃的不对称烷基化反应, 化学产率最高达85%, 对映体过量值最高达95% ee.     

Cyclisierungen unter beteiligung von fluoridionen, 3. Mittell. [1,2] teilfluorierte 1.3- und 1.4-dioxane

Cyclization of 2-(2-chloroethoxy)-perfluorocarboxylic acid halides 3 with alkali metal fluoride gives 2.3-perfluoro- 1.4-dioxanes 6 with yields up to 84 %. This reaction is also used for the preparation of 4.5.6-perfluoro-1.3- dioxanes 12 starting from 3-chloromethoxyperfluorocarbonyl compounds 11. — The preparation of starting materials is described.     

The Reactions Between Sodium Hydrogen Telluride and Ar3CX,Ar2CHX,ArCH2X

Tertiary, secondary and primary benzylic halides give dehalogenated, coupling and oxidized product after reacted with sodium hydrogen telluride in DMF. The yields are 87%, 48% and 40%–56%, respectively.     

Reaction of trialkylsilanes with phenol in the presence of metal halides

Summary We studied the reaction of phenol with trialkylsilanes of various structures, catalyzed by metal halides. The most suitable halides for this reaction are those of Cr, Co, Ni, Ge, Zn, Sn, and Hg. The reaction rate depends on the structure of the trialkylsilane and the amount and nature of the metal halides.The reaction of trialkylsilanes with phenol, catalyzed by metal halides, is a simple and convenient method of synthesizing trialkylphenoxysilanes, which are formed in yields of up to 98% of theoretical.We synthesized 16 trialkylphenoxysilanes (13 of which were prepared for the first time) and determined their properties. 16 trialkylsilanes were prepared as starting materials and 8 of these were described for the first time.     

Highly enantioselective synthesis of chiral allenes by sequential creation of stereogenic center and chirality transfer in a single pot operation

Chiral allenes are readily accessed in a single pot operation in the reaction of terminal alkynes, aldehydes, chiral secondary amines, and zinc halides in good yields (up to 77% yield) and excellent enantioselectivities (up to 99% ee) in toluene at 120 °C. The reaction proceeds through initial formation of chiral propargylamine intermediates with creation of a new stereogenic center and subsequent chirality transfer via an intramolecular hydride shift to produce chiral allenes with high enantiomeric purities.     

Stille coupling approaches for the synthesis of 8-aryl guanines

The reaction of 8-bromoguanines with aryl and hetaryl stannanes in the presence of a palladium catalyst leads to the formation of the corresponding 8-aryl(hetaryl)guanines. It was found that the addition of triphenylarsine or triphenylbismuth strongly reduces the reaction time and increases product yields.     

A convenient and efficient preparation of β-substituted α-haloenones from diazodicarbonyl compounds

Rhodium(II)-catalyzed reactions of cyclic diazodicarbonyl compounds with a variety of halides have been examined. With acid halides, β-acyloxy α-haloenones are produced in good yields. With benzyl halides, β-benzyloxy α-haloenones are obtained in good yields. Reactions with methylene halides yield β-halomethoxy α-haloenones in good yields, whereas reactions with ethyl halides and ethylene dihalides result in β-hydroxy α-haloenones in high yields. These reactions provide a useful and rapid entry to β-substituted α-haloenones. The mechanistic pathway for the formation of these products has been also described in terms of halonium ylides.