Α-halocarbonyl Compounds Research Articles

Enantioselective Protonation of Silyl Enol Ethers and Ketene Disilyl Acetals with Lewis Acid-Assisted Chiral Brønsted Acids: Reaction Scope and Mechanistic Insights

Enantioselective protonation is a potent and efficient way to construct chiral carbons. Here we report details of the reaction using Lewis acid-assisted chiral Brønsted acids (chiral LBAs). The 1:1 coordinate complex of tin tetrachloride and optically active binaphthol ((R)- or (S)-BINOL) can directly protonate various silyl enol ethers and ketene disilyl acetals to give the corresponding α-aryl ketones and α-arylcarboxylic acids, respectively, with high enantiomeric excesses (up to 98% ee). A catalytic version of enantioselective protonation has also been achieved using stoichiometric amounts of 2,6-dimethylphenol and catalytic amounts of monomethyl ether of optically active BINOL in the presence of tin tetrachloride. This protonation is also effective for producing α-halocarbonyl compounds (up to 91% ee). DFT calculations on the B3LYP/LANL2DZ level show that the conformational structure of the chiral LBA and the orientation of activated proton on (R)-BINOLs are important for understanding the absolute stereochemistry of the products.

Indium Metal and Its Halides in Organic Synthesis

This review highlights the applications of indium metal and indium(III) halides in organic synthesis with particular reference to regio-, stereo-, and chemoselectivity. Indium-mediated reactions include the regioselective allylation of alkynes, the stereoselective debromination of vic-aryl-substituted dibromides, the homocoupling of alkyl/aryl halides, and the reduction of α-halocarbonyl compounds. Indium trichloride has been used as a Lewis acid catalyst in epoxide rearrangements, in the synthesis of α-amino phosphonates, and in the construction of the quinoline system. Indium triiodide has proven to be a very efficient catalyst for transesterification processes.

Indium-mediated reductive dehalogenation of α-halocarbonyl compounds in water†

Reactions of various α-halocarbonyl compounds 1 with indium in the presence of a catalytic amount of sodium dodecyl sulfate in water were performed to afford the corresponding parent carbonyl compounds 2 in excellent yields.

Indium as a reducing agent. Chemoselective reduction of α-halocarbonyl compounds and benzyl halides by indium metal in water under sonication

Indium metal in water reduces α-halocarbonyl compounds and benzyl iodides to the corresponding dehalogenated products in excellent yields under sonication although simple alkyl and aryl iodides remained inert under these conditions.

On the synthesis of (S)-α-methylaspartic acid by diastereoselective alkylation of a chiral 2-cyanopropanoate

Abstract A novel and efficient procedure for the synthesis of optically pure α-methylaspartic acid, based on the diastereoselective alkylation of (1 S ,2 R ,4 R )-10-(dicyclohexylsulfamoyl)isobornyl 2-cyanopropanoate with α-halocarbonyl compounds, is described.

A novel one-pot reformatsky type reaction via bismuth salt in aqueous media

In the presence of bismuth(III)chloride-metallic aluminum, α-halo carbonyl compounds react with aldehydes in water under mild conditions to give β-hydroxy carbonyl compounds with stereoselectivity in good yields.

Electrochemical Deacetylation of 1,3-Dicarbonyl Compounds

Abstract Mild deacetylation of 1,3-dicarbonyl compounds was achieved by halonium-ion mediated electrolysis. In this reaction, the supporting electrolyte including sodium halide NaX (X = Cl or Br) was essential since the reaction proceeded through substitution by a halonium ion, generated electrochemically at anode, on active methine carbons followed by base-catalyzed deacetylation, and was terminated by reductlve dehalogenation of the formed α-halo carbonyl compounds at cathode.

Controlled Radical Polymerization of Methacrylic Monomers in the Presence of a Bis(ortho-chelated) Arylnickel(II) Complex and Different Activated Alkyl Halides

A novel class of homogeneous nickel(II) catalysts, i.e [Ni{o,o‘(CH2NMe2)2C6H3}Br], denoted as Ni(NCN‘)Br, is reported to mediate in the presence of activated alkyl halides, e.g., CCl4 or α-halocarbonyl compounds, a well-controlled radical polymerization of methacrylic monomers [methyl and n-butyl methacrylate), (MMA, n-BuMA)] at rather low temperatures (<100 °C). The number-average molecular weight of the polymer gradually increased with the monomer conversion and was inversely proportional to the initiator concentration of alkyl halides. The molecular weight distribution (MWD) remained very narrow during the whole course of the polymerization (MWD < 1.3). All the experimental data including a successful block copolymerization (n-BuMA-b-MMA) experiment were in agreement with a living polymerization process, and remarkably enough, poly(methyl methacrylate) (PMMA) with molecular weight up to at least 105 g/mol was synthesized in a controlled fashion. Increased thermal stability of the PMMA is a further indi...

Generation and Reaction of Samarium(II) Iodide Equivalent from Samarium and Chlorotrimethylsilane/Sodium Iodide System in Acetonitrile

Abstract Samarium(II) iodide equivalent was generated from metallic samarium and Me3SiCl/Nal reagent in acetonitrile under ambient conditions. Dehalogenation of α-halocarbonyl compounds and reductive coupling of ketones were successfully carried out by the use of the samarium(II) species, thus generated, in acetonitrile.

Dehalogenation of α-Halo Carbonyl Compounds by a New Efficient Reagent, Triphenylphosphonium Iodide

Abstract Triphenylphosphonium iodide, Ph3PHI, was found to be an efficient reagent for the dehalogenation of α-halo carbonyl compounds. α-Halo esters, which were difficult to be reduced with Me3SiCl/Nal reagent, was smoothly debrominated by Ph3PHI. Treatment of α-halocarbonyl compounds with Ph3PDI produced the corresponding α-deuterated compounds.

Cyclization reactions of nitriles

The interaction of 2-thienylidene derivatives of malononitrile and cyanothio-acetamide with methylene active nitriles gives 2,6-diamino-3,5-dicyano-4-(2-thienyl)-4H-thiopyran which is smoothly recrystallized into 6-amino-3,5-dicyano-4-(2-thienyl)-2(1H)-pyridinethione. The latter is easily alkylated at the sulfur atom by α-halocarbonyl compounds. This reaction was used in the synthesis of 3,6-diamino-4-(2-thienyl)thieno[2,3-b]pyridines.

Cyclopentenones from Allylidene Triphenylphosphoranes and α-Halocarbonyl compounds

Allylidene triphenylphosphorane 3 reacted with α-haloketones and α-halothioesters to give 2-ethoxycyclopentadienes via a [3+2] annulation process in the presence of base. Mild acid treatment of the 2-ethoxycyclopentadienes provided a new route to cyclopentenones.

Aluminium triiodide mediated reductive dehalogenation of α-halocarbonyl compounds and trapping of the aluminium enolate intermediate via aldol reaction

Aluminium triiodide has been conveniently used for reductive dehalogenation and aldol condensation of α-halocarbonyl compounds via aluminium enolate.

Synthesis and deamination of 9-aminoimadazo[1,2-a]benzimidazoles

The reaction between 1,2-diaminobenzimidazole and α-halocarbonyl compounds has given some novel 9-aminoimidazo [1,2-a]benzimidazoles. On treatment with nitrous acid or potassium hydroxide in DMSO, these compounds give, in addition to the deaminated compounds, 3-nitroso-derivatives of the deamination products. In the system DMSO-KOH, 9-benzylideneaminoimidazobenzimidazoles are converted smoothly into 1(9H)-imidazobenzimidazoles. It is shown that 3-nitroso-derivatives which are unsubstituted in the NH group exist predominantly in the hydroxyimino form.

ChemInform Abstract: Reaction of Bis(trimethylsiloxy)phosphine with α‐Halo Carbonyl Compounds. A New Route to Substituted O,O‐Divinyl O‐Trimethylsilyl Phosphates.

ChemInformVolume 21, Issue 9 Organoelement Compounds ChemInform Abstract: Reaction of Bis(trimethylsiloxy)phosphine with α-Halo Carbonyl Compounds. A New Route to Substituted O,O-Divinyl O-Trimethylsilyl Phosphates. P. MAJEWSKI, P. MAJEWSKI Inst. Org. Chem., Tech. Univ., PL-90-924 Lodz, Pol.Search for more papers by this author P. MAJEWSKI, P. MAJEWSKI Inst. Org. Chem., Tech. Univ., PL-90-924 Lodz, Pol.Search for more papers by this author First published: February 27, 1990 https://doi.org/10.1002/chin.199009259Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume21, Issue9February 27, 1990 RelatedInformation

Reaction of 1,1-dichloro-1-nitrosoalkanes with acid chlorides and zinc

1,1-Dichloro-1-nitrosoalkanes, similar to α-halocarbonyl compounds, react with acid chlorides and zinc to give O- acylated acylhydroximoyl chlorides.

The reaction of allylidene triphenylphosphoranes with α-halocarbonyl compounds: a convenient synthesis of cyclopentadienes

A convenient method has been developed for the synthesis of substituted cyclopentadienes, starting from allylidene triphenylphosphoranes and α-halocarbonyl compounds, via a [3 + 2] annulation process.

Crossed aldol type condensation reactions in aqueous media

Directed crossed aldol type condensations can be carried out in aqueous media using α-halocarbonyl compounds, aldehydes, and metallic zinc or tin.

REACTION OF BIS(TRIMETHYLSILOXY)PHOSPHINE WITH α-HALO CARBONYL COMPOUNDS. A NEW ROUTE TO SUBSTITUTED O,O-DIVINYL-O-TRIMETHYLSILYL PHOSPHATES

Abstract Substituted 0.O-divinyl-O-trimethylsilyl phosphates 4 have been obtained in satisfactory yields by reacting bis(trimethylsiloxy)phosphine (1) with α-halo carbonyl compounds 2 in the presence of chlorotrimethylsilane and triethylamine.

Sodium Telluride-Mediated Sulfenylation of α-Halo Carbonyl Compounds with Diphenyl Disulfide

Abstract Under mild aprotic conditions α-halo carbonyl compounds react with diphenyl disulfide in the presence of sodium telluride to give the corresponding α-phenylthio derivatives in good to moderate yields. The reaction appears to proceed involving the sulfur–sulfur bond cleavage of diphenyl disulfide by sodium telluride.