27644-18-4Relevant academic research and scientific papers
Indium- and Zinc-Mediated Acyloxyallylation of Protected and Unprotected Aldotetroses - Revealing a Pronounced Diastereodivergence and a Fundamental Difference in the Performance of the Mediating Metal
Draskovits, Markus,Stanetty, Christian,Baxendale, Ian R.,Mihovilovic, Marko D.
, p. 2647 - 2659 (2018/03/09)
The acyloxyallylation of unprotected aldoses was first demonstrated more than a decade ago as a potentially elegant two-carbon homologation of reducing sugars (upon ozonolysis); however, its application in real case syntheses remained scarce. Following up on such a successful showcase and to answer several pending questions about this attractive transformation, we engaged in an in depth methodological reinvestigation. The epimeric tetroses l-erythrose and d-threose in unprotected and protected form were successfully applied to the indium and also zinc-mediated acyloxyallylation, with the latter being a first for an unprotected sugar. The investigation largely benefited from the choice of these more exotic starting materials as it allowed unambiguous identification/quantification of the hexose-products which are available as authentic reference materials. The observed diastereoselectivities indicate a strong substrate control (stereochemistry at O2), and the influence of the reagent's structure on the selectivity was investigated in great detail. A strong facial diastereodivergence between related protected and unprotected structures was demonstrated and an unexpected, pronounced principle difference in performance between indium and zinc was revealed.
Aerobic oxidative esterification and thioesterification of aldehydes using dibromoisocyanuric acid under mild conditions: No metal catalysts required
Kwon, Young-Do,La, Minh Thanh,Kim, Hee-Kwon
, p. 10833 - 10841 (2018/07/05)
A practical direct method for the direct preparation of esters and thioesters from aldehydes is described. Esters and thioesters were synthesized by oxidative esterification and thioesterification via in situ generated acyl bromide intermediates, which were used to react with various alcohols and thiols. The esterification and thioesterification were readily performed in the presence of dibromoisocyanuric acid in dichloromethane, without any metal catalysts and under mild conditions. By using this reaction protocol, various esters and thioesters were prepared in high yields. This effective method offers a promising approach for the facile esterification and thioesterification of aldehydes.
Selective C(sp2)-H Halogenation of "click" 4-Aryl-1,2,3-triazoles
Goitia, Asier,Gómez-Bengoa, Enrique,Correa, Arkaitz
supporting information, p. 962 - 965 (2017/02/26)
Selective bromination reactions of "click compounds" are described. Electron-neutral and electron-deficient arenes selectively undergo unprecedented Pd-catalyzed C-H ortho-halogenations assisted by simple triazoles as modular directing groups, whereas electron-rich arenes are regioselectively halogenated following an electrophilic aromatic substitution reaction pathway. These C-H halogenation procedures exhibit a wide group tolerance, complement existing bromination procedures, and represent versatile synthetic tools of utmost importance for the late-stage diversification of "click compounds". The characterization of a triazole-containing palladacycle and density functional theory studies supported the mechanism proposal.
A mild method for the replacement of a hydroxyl group by halogen. 1. Scope and chemoselectivity
Munyemana, Fran?ois,George, Isabelle,Devos, Alain,Colens, Alain,Badarau, Eduard,Frisque-Hesbain, Anne-Marie,Loudet, Aurore,Differding, Edmond,Damien, Jean-Marie,Rémion, Jeanine,Van Uytbergen, Jacqueline,Ghosez, Léon
, p. 420 - 430 (2015/12/31)
α-Chloro-, bromo- and iodoenamines, which are readily prepared from the corresponding isobutyramides have been found to be excellent reagents for the transformation of a wide variety of alcohols or carboxylic acids into the corresponding halides. Yields are high and conditions are very mild thus allowing for the presence of sensitive functional groups. The reagents can be easily tuned allowing therefore the selective monohalogenation of polyhydroxylated molecules. The scope and chemoselectivity of the reactions have been studied and reaction mechanisms have been proposed.
Synthesis of n-alkyl terminal halohydrin esters from acid halides and cyclic ethers or thioethers under solvent- and catalyst-free conditions
Venkatesham, Kunuru,Chanti Babu, Dokuburra,Bharadwaj, Tatipamula Vinay,Bunce, Richard A.,Rao, Chitturi Bhujanga,Venkateswarlu, Yenamandra
, p. 51991 - 51994 (2014/12/11)
An efficient and eco-friendly protocol has been developed for the preparation of n-alkyl terminal halohydrin esters under solvent- and catalyst-free conditions. Ring opening of cyclic ethers by organic acid halides affords the 1,4- and 1,5-halohydrins, OH-protected by different acyl groups. The green reaction conditions, simple work-up procedures, high yields and broad substrate scope of the reaction highlight the positive features of this method. This journal is
A mild and efficient reaction for conversion of carboxylic acids into acid bromides with ethyl tribromoacetate/triphenylphosphine under acid-free conditions
Kang, Dong Ho,Joo, Tae Young,Lee, Eun Hwa,Chaysripongkul, Skaydaw,Chavasiri, Warinthorn,Jang, Doo Ok
, p. 5693 - 5696 (2007/10/03)
Acid bromides were prepared efficiently from carboxylic acids with readily available ethyl tribromoacetate and triphenylphosphine at room temperature under neutral conditions. The present process is applicable to the preparation of various acid bromides from aromatic and aliphatic carboxylic acids. Aromatic carboxylic acids were found to be more reactive than aliphatic carboxylic acids under reaction conditions.
Triphenylphosphine-2,4,4,6-tetrabromo-2,5-cyclohexadienone complex as a reagent for preparation of carboxylic acid bromides
Matveeva,Podrugina,Sandakova,Zefirov
, p. 1469 - 1472 (2007/10/03)
Triphenylphosphine-2,4,4,6-tetrabromo-2,5-cyclohexadienone complex was successfully used as a new reagent for the synthesis of carboxylic acid bromides which were isolated as individual substances or were identified by conversion into the corresponding anilides. The reaction is chemoselective, and it can be applied to polyfunctional compounds, e.g., hydroxy acids.
CARBONYLATION OF TERTIARY ALKYL HALIDES, SYNTHESIS OF PIVALOYL HALIDES
Brunet, J.-J.,Legars, P.,Peres, Y.,Tkatchenko, I.,Lecolier, S.
, p. 4569 - 4572 (2007/10/02)
The carbonylation of tert-butyl halides in a two-phase system, RSO3H/CCl4, under carbon monoxide pressure affords the corresponding pivaloyl halides in good yields and selectivities.
Reaction of Hindered Trialkylsilyl Esters and Trialkylsilyl Ethers with Triphenylphosphine Dibromide: Preparation of Carboxylic Acid Bromides and Alkyl Bromides under MIld Neutral Conditions
Aizpurua, Jesus M.,Cossio, Fernando P.,Palomo, Claudio
, p. 4941 - 4943 (2007/10/02)
A new route for a simultaneous deprotection-activation of hindered trialkylsilyl esters is described. tert-Butyldimethylsilyl, triisopropylsilyl, and tert-butyldiphenylsilyl carboxylates reacted with triphenylphosphine dibromide at room temperature in dichloromethane to give acid bromides in high yields.Reaction between hindered trialkylsilyl ethers and triphenylphosphine dibromide afforded alkyl bromides in excellent yields.The formation rate of acid bromides and alkyl bromides was increased when the reactions were carried out in the presence of a catalytic amount of ZnBr2.
