Oxidation of organoboranes containing primary alkyl groups with pyridinium chlorochromate. A direct synthesis of aldehydes from terminal alkenes

Organoboranes derived from terminal olefins are oxidized by pyridinium chlorochromate to aldehydes in good yields.     

A.C. polarographic determination of unsaturation

A wide range of olefins can be determined by a.c. polarography of their addition compounds with mercuric acetate. The first step in the reduction of these compounds is a reversible, one-electron process to form the organo-mercury radical and gives a well defined a.c. peak. The optimum conditions for the determination of a representative selection of olefins has been established.     

Two-carbon homologation of aldehydes via silyl ketene acetals. 2. Study of the stereochemical control in the formation of (E)-alkenoic acids.

The condensation of C,O,O-tris(trimethylsilyl)ketene acetal 1 with aldehydes 2 in the presence of catalytic amounts of mercuric iodide at room temperature affords syn and anti beta-trimethylsiloxy alpha-trimethylsilyl alkanoic acid silyl esters 3 in good yields. These new compounds gave, under acidic or basic conditions, E and (or) Z enoic acids 4. The paths for the formation of these alkenoic acids are discussed.     

一个新的Cu(II)-二胺配合物催化的Henry反应

研究了L-脯氨酸制得的C2-对称二胺,与醋酸铜形成新的配合物,催化各种醛与硝基烷烃间的Henry反应。 考察了反应温度、溶剂和催化剂用量对收率和反应速率的影响。 研究结果表明,在室温下,以乙醇作为反应溶剂时,摩尔分数10%的二胺醋酸铜配合物能够有效地催化醛与硝基甲烷反应,生成相应的β-硝基醇,收率为60%~92%。 醛与硝基乙烷的Henry反应产物具有非对映立体选择性。 芳香醛参与Henry反应产物的非对映选择性高达24∶1,但脂肪醛为底物时,此催化剂对Henry反应的非对映选择性不明显。     

Solvolytic cleavage of alkenylpentafluorosilicates catalyzed by copper(II) acetate. A stereoselective synthesis of (E)-alkenyl ethers from alkynes

(E)-Alkenylpentafluorosilicates, obtainable from acetylenes via hydrosilylation-silicate formation, react with alcohols in the presence of a catalytic amount of copper(II) acetate under an atmosphere of air (oxygen) at room temperature to form (E)-alkenyl ethers stereoselectively in satisfactory yields. Similar reaction with water gives aldehydes.     

Mercuric Acetate in Organic Synthesis: A Simple Procedure for the Synthesis of Pyrazolines1

Reaction of aldehyde hydrazones (1) with mercuric acetate leads to the formation of nitrile imines (2) which can react insitu with olefins to produce 1,3,5-trisubstituted 2-pyrazolines (4) in good yield.     

Metal Carbonyl Spectra : by P.S. Braterman,Academic Press,London/New York/San Francisco, 1975, vii + 286 pages, $22.25.

Vinyl halides react with alkyllithium compounds in the presence of tetrakis(triphenylphosphine)palladium to give olefins stereospecifically in excellent or fairly good yields. When less reactive Grignard reagents are employed instead of alkyllithium compounds, these reactions can be carried out catalytically with palladium.     

Oxidation of azides by the HOF.CH3CN: a novel synthesis of nitro compounds

The HOF.CH3CN complex, readily prepared by passing F2 through aqueous acetonitrile, is an exceptionally efficient oxygen transfer agent. It is unique in its capacity to oxidize various azides into the corresponding nitro derivatives. This method requires short reactions times and room temperature or below, and the desired nitro compounds were usually isolated in very good yields. The respective nitroso derivatives are believed to be the intermediates in this reaction. Functional groups such as aromatic rings, ketones, nitriles, halides, alcohols, and esters are tolerated. Sulfides react with HOF.CH3CN usually at the same rate as azides. Amines and olefins, however, react faster, so they have to be protected first. Nitro derivatives with various oxygen isotopes can be made using the labeled H18OF.CH3CN. In the case of chiral azides the stereochemistry around the nitrogen-bonded carbons is retained.     

Hydroboration. 97. Synthesis of new exceptional chloroborane--Lewis base adducts for hydroboration. Dioxane--monochloroborane as a superior reagent for the selective hydroboration of terminal alkenes

Several less volatile oxygen-containing Lewis bases, such as tert-butyl methyl ether, dioxane, anisole, ethyl acetate, beta-chloroethyl ether, and monoglyme, were examined as prospective mono- and dichloroborane carriers. Dioxane, ethyl acetate, and beta-chloroethyl ether form relatively stable boron trichloride adducts, but the boron trichloride adduct of monoglyme is not very stable and must be used immediately. On the other hand, tert-butyl methyl ether and anisole fail to form stable boron trichloride adducts and the corresponding ether-cleaved products are obtained. Among the selected oxygen-containing Lewis bases, only dioxane forms stable and reactive mono- and dichloroborane adducts. Monoglyme and beta-chloroethyl ether give stable dichloroborane adducts requiring excess of diborane. Convenient methods for the preparation of mono- and dichloroborane adducts of dioxane from dioxane-BCl(3) and NaBH(4) in the presence of catalytic amounts of tri- or tetraglyme were developed. The dioxane--monochloroborane adduct hydroborates representative olefins cleanly and rapidly. The corresponding alcohols were obtained in quantitative yields after oxidation. Also, the hydroboration of several terminal olefins with dioxane--monochloroborane were highly regioselective and the primary alcohols were obtained almost exclusively (>99.5%), after oxidation. Accordingly, dioxane-monochloroborane should serve as a reagent of choice for such hydroborations. The dioxane--dichloroborane adduct showed remarkable selectivity toward 2-substituted terminal olefins, such as 2-methyl-1-butene and beta-pinene, when compared to simple terminal and hindered olefins, giving a unique tool for selective hydroborations. Dichloroborane adducts of monoglyme and beta-chloroethyl ether also showed high reactivity, even at room temperature, toward simple unhindered olefins. However, hydroboration of hindered olefins is slow and requires either higher temperatures or the addition of 1 equiv of boron trichloride to liberate free dichloroborane, as in the case of the previously known dichloroborane adducts of methyl sulfide and diethyl ether.     

A simple and facile method for regio- and stereoselective bromoformyloxylation and bromoacetoxylation of olefins using NH4Br and oxone®

A mild and efficient protocol for the preparation of bromoformates as well as bromoacetates from olefins using NH₄Br and oxone® in nucleophile sources (DMF or DMA) without employing catalyst at room temperature is described. This method is facile, environmentally friendly and cost effective. A variety of terminal, internal and cyclic alkenes reacted smoothly to give the corresponding bromoformate and acetate products in good to excellent yields. Moreover, 1,2-disubstituted olefins provided moderate to excellent diastereoselectivity.     

Palladium-imidazolium carbene catalyzed Mizoroki-Heck coupling with aryl diazonium ions

[reaction: see text] Catalyst formed from N,N-bis(2,6-diisopropylphenyl)dihydroimidazolium chloride and palladium(II) acetate (2 mol %) was used, without added base, to efficiently produce Heck coupled products with olefins and aryl diazonium tetrafluoroborate substrates. The reactions were performed at room temperature, giving product in 2-4 h with 80-90% yields for isolated materials. Diazonium ions, formed in situ directly from anilines, also couple under these conditions.     

Addition of benzylzinc halides to alkenyl(phenyl)iodonium triflates: stereoselective synthesis of trisubstituted alkenes

Benzylic organozinc reagents generated by insertion of zinc metal into benzyl-bromine bonds react with alkenyl(phenyl)iodonium triflates to provide single stereoisomers of trisubstituted olefins. The extremely high reactivity of the phenyliodonio moiety allows these reactions to be performed in the absence of copper salts or palladium catalysts. The reaction is performed from -40 degrees C to room temperature in THF. Excellent yields of the desired cross-coupled products have been obtained despite the occurrence of a competing electron-transfer-induced fragmentation.     

A convenient synthesis of olefins via deacylation reaction

A convenient and environmentally-friendly synthetic method of olefins via deacylation reaction is described. The reaction gives olefins by condensation of aldehydes with a variety of 1,3-dicarbonyl compounds in the presence of anhydrous potassium carbonate at room temperature in high yields (70-90%) in one step. The synthetic potential of this strategy can be used as an alternative procedure to the Wittig, Wittig-Horner reactions. The stereochemistry of the resulted olefins was determined by NOE experiment with correct radio frequency and X-ray analysis. The E/Z selectivity of the deacylation reaction depends on the α-substituents of the 1,3-dicarbonyl compounds.     

Organoboranes for synthesis. 9. Rapid reaction of organoboranes with iodine under the influence of base. a convenient procedure for the conversion of alkenes into iodides via hydroboration

The reaction of organoborane with iodine is strongly accelerated by sodium hydroxide. Organoboranes derived from terminal alkenes react with the utilization of approximately two of the three alkyl groups attached to boron, providing a maximum of 67% yield of alkyl iodide. Thus, hydroboration-iodination of 1-decene gives a 60% yield ofn-decyl iodide. Secondary alkyl groups, derived from internal alkenes, react more sluggishly and only one of the three alkyl groups attached to boron is converted to the iodide. Thus, the procedure applied to 2-butene provides a 30% yield of 2-butyl iodide. The use of disiamylboranebis-(3-methyl-2-butylborane, Sia₂BH) as hydroborating agent increases the yield of iodides from terminal alkenes since the primary alkyl groups react in preference to the secondary siamyl groups. Consequently, hydroboration of 1-decene with Sia₂BH, followed by iodination gives a 95% yield ofn-decyl iodide. The use of methanolic sodium methoxide in place of sodium hydroxide provides alkyl iodides in considerably higher yields. The combination of hydroboration with iodination in the presence of a base provides a convenient method for theanti-Markovnikov hydroiodination of alkenes. The base-induced iodination of organoboranes proceeds with the inversion of configuration at the reaction center, as shown by the formation ofendo-2iodonorbomane from tri-exo-norbomylborane.     

Efficient syntheses of heterocycles and carbocycles by electrophilic cyclization of acetylenic aldehydes and ketones

Highly substituted oxygen heterocycles can be prepared in good yields at room temperature by reacting o-(1-alkynyl)-substituted arene carbonyl compounds with NBS, I(2), ICl, p-O(2)NC(6)H(4)SCl, or PhSeBr and various alcohols or carbon-based nucleophiles. Naphthyl ketones and iodides are readily prepared by the reaction of 2-(1-alkynyl)arene-carboxaldehydes with I(2) and simple olefins or alkynes.     

Chiral Phosphorus–Olefin Ligands for the RhI‐Catalyzed Asymmetric Addition of Aryl Boronic Acids to Electron‐Deficient Olefins

New chiral phosphorus–olefin hybrid ligands derived from the rigid “privileged” l ‐proline have been conveniently prepared and applied in the rhodium‐catalyzed asymmetric arylation of electron‐deficient olefins with arylboronic acids at room temperature; this reaction provides the desired products in excellent yields and high enantioselectivities. The origin of observed stereoselectivity has been investigated by density functional theory (DFT) calculations.     

Effect of Metal Ions in Organic Synthesis. part XVI. Knoevenagel Condensations of Aldehydes and Tosylhydrazones with 2,4-Pentanedione by Copper (II) Chloride-Catalyzed Reaction

Based on some of our previous findings on the activity of some metal ions in certain organic reactivities,¹ we have now studied the Knoevenagel condensations of aliphatic and aromatic aldehydes or their tosylhydrazone derivatives with 2,4-pentanedione. In the presence of catalytic amounts of anhydrous copper (II) chloride, these compounds react in tetrahydrofuran at room temperature, affording the corresponding alkylidene or arylidene compounds in 48–98% yields.     

Diacetoxyiodobenzene-mediated oxidative addition of 1,3-dicarbonyl compounds to olefins: an efficient one-pot synthesis of 2,3-dihydrofuran derivatives

A variety of olefins react with -dicarbonyl compounds at 0°C in the presence of diacetoxyiodobenzene to afford highly substituted 2,3-dihydrofuran derivatives in good to excellent yields.     

Triphenylphosphine-Promoted Synthesis of Spiroketals from Phthalic Anhydride with Dialkyl Acetylenedicarboxylates

Triphenylphosphine, dialkyl acetylenedicarboxylates, and phthalic anhydride react in one pot to afford novel spirocyclic compounds in fairly good yields at room temperature.     

Catalytic epoxidation of aliphatic terminal olefins with sodium hypochlorite

Meso-tetra(halogenophenyl)porphyrinatomanganese complexes catalyze the epoxidation of terminal olefins by sodium hypochlorite at room temperature; moderate to good yields of epoxides are obtained.