- LiHMDS: Facile, highly efficient and metal-free transesterification under solvent-free condition
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Transesterification is one of the important organic reactions employed in numerous industrial as well as laboratory applications for the synthesis of various esters. Herein, we report a rapid, highly efficient, and transition metal-free transesterification reaction in the presence of LiHMDS under solvent-free conditions. The transesterification reaction was carried out with three different benzoate esters and a wide range of primary and secondary alcohols (from C3-C18) in good to excellent yields (45 examples). By considering the commercial role of esters, this method will be promising for the facile synthesis of esters in industry-relevant applications.
- Gore, Kiran R.,Mittapelli, Lavanya L.
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- Enolate-Based Regioselective Anti-Beckmann C-C Bond Cleavage of Ketones
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The Baeyer-Villiger or Beckmann rearrangements are established methods for the cleavage of ketone derivatives under acidic conditions, proceeding for unsymmetrical precursors selectively at the more substituted site. However, the fragmentation regioselectivity cannot be switched and fragmentation at the less-substituted terminus is so far not possible. We report here that the reaction of ketone enolates with commercial alkyl nitrites provides a direct and regioselective way of fragmenting ketones into esters and oximes or ω-hydroxyimino esters, respectively. A comprehensive study of the scope of this reaction with respect to ketone classes and alkyl nitrites is presented. Control over the site of cleavage is gained through regioselective enolate formation by various bases. Oxidation of kinetic enolates of unsymmetrical ketones leads to the otherwise unavailable "anti-Beckmann"cleavage at the less-substituted side chain, while cleavage of thermodynamic enolates of the same ketones represents an alternative to the Baeyer-Villiger oxidation or the Beckmann rearrangement under basic conditions. The method is suited for the transformation of natural products and enables access to orthogonally reactive dicarbonyl compounds.
- Jahn, Ullrich,Ma?ek, Tomá?
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p. 11608 - 11632
(2021/09/02)
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- Zn-Mediated Hydrodeoxygenation of Tertiary Alkyl Oxalates
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Herein we describe a general, mild, and scalable method for hydrodeoxygenation of readily accessible tertiary alkyl oxalates by Zn/silane under Ni-catalyzed conditions. The reduction method is suitable for an array of structural motifs derived from tertiary alcohols that bear diverse functional groups, including the synthesis of a key intermediate en route to estrone.
- Ye, Yang,Ma, Guobin,Yao, Ken,Gong, Hegui
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supporting information
p. 1625 - 1628
(2021/01/18)
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- Hydrogenation of alkenes via cooperative hydrogen atom transfer
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Radical hydrogenation via hydrogen atom transfer (HAT) to alkenes is an increasingly important transformation for the formation of thermodynamic alkane isomers. Current single-catalyst methods require stoichiometric oxidant in addition to hydride (H-) source to function. Here we report a new approach to radical hydrogenation: cooperative hydrogen atom transfer (cHAT), where each hydrogen atom donated to the alkene arrives from a different catalyst. Further, these hydrogen atom (H?) equivalents are generated from complementary hydrogen atom precursors, with each alkane requiring one hydride (H-) and one proton (H+) equivalent and no added oxidants. Preliminary mechanistic study supports this reaction manifold and shows the intersection of metal-catalyzed HAT and thiol radical trapping HAT catalytic cycles to be essential for effective catalysis. Together, this unique catalyst system allows us to reduce a variety of unactivated alkene substrates to their respective alkanes in high yields and diastereoselectivities and introduces a new approach to radical hydrogenation.
- Kattamuri, Padmanabha V.,West, Julian G.
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supporting information
p. 19316 - 19326
(2020/11/13)
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- Metal catalyst-free photo-induced alkyl C-O bond borylation
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Metal catalyst free, blue visible light-induced C-O bond borylation of unactivated tertiary alkyl methyl oxalates has been developed to furnish tertiary alkyl boronates. From the secondary alcohols activated with imidazolylthionyl, moderate yields of boronates were attained under standard photo-induced conditions. Preliminary mechanistic studies confirmed the involvement of a (DMF)2-B2cat2 adduct that weakly absorbs light at 437 nm so as to initiate a Bcat radical. A radical-chain process is proposed wherein the alkyl radical is engaged. This journal is
- Chen, Changzhou,Gong, Hegui,Lei, Chuanhu,Ma, Guobin,Talukdar, Sangita,Zhao, Xinluo
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p. 10219 - 10222
(2020/09/18)
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- Method for reductive hydrogenation of tertiary alkyl alcohol
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The invention discloses a method for reductive hydrogenation of tertiary alkyl alcohol. The method comprises the following steps: using oxalic ester prepared from tertiary alkyl alcohol in advance asa raw material, reacting at 40-60 DEG C for 8-12 hours under the actions of a nickel source, a ligand, a hydrogen donor, a reducing agent, an additive and a solvent to obtain a product of reductive hydrogenation of tertiary alkyl alcohol. Tertiary alkyl oxalate prepared from tertiary alkyl alcohol is used as a reaction precursor, zinc powder/magnesium chloride is used as a medium for catalytic reduction of non-activated tertiary alkyl oxalate, nickel promotes breakage of C-O bonds of oxalate, and diphenyl silane is used as a hydrogen donor for preparation of a reduction product. According to the method, the adopted catalyst metal is cheap, the raw materials are simple and easy to obtain, the reaction is mild and one-step, the steps are simple, the operation is safe, the yield is high, andthe cost is low.
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Paragraph 0033-0045
(2020/07/15)
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- Iron-Catalyzed Reductive Vinylation of Tertiary Alkyl Oxalates with Activated Vinyl Halides
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We present herein a rare and efficient method for the creation of vinylated all carbon quaternary centers via Fe-catalyzed cross-electrophile coupling of vinyl halides with tertiary alkyl methyl oxalates. The reaction displays excellent functional group tolerance and broad substrate scope, which allows cascade radical cyclization and vinylation to afford complex bicyclic and spiral structural motifs. The reaction proceeds via tertiary alkyl radicals, and the putative vinyl-Br/Fe complexation appears to be crucial for activating the alkene and enabling a possibly concerted radical addition/C-Fe forming process.
- Chen, Haifeng,Gong, Hegui,Yao, Ken,Ye, Yang
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supporting information
(2020/03/13)
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- Pd-Colloids-Catalyzed/Ag2O-Oxidized General and Selective Esterification of Benzylic Alcohols
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Palladium colloids obtained from the degradation of Hermann–Beller palladacycle proved to be an efficient catalytic system in combination with silver oxide as a selective oxidant for the oxidative esterification of differently substituted benzyl alcohols in MeOH as solvent. Excellent reactivity exhibited by the catalytic system also allowed the alcoholic coupling partner to be changed from MeOH to a wide range of alcohols having diverse functionalities. The mildness of the developed protocol also made it possible to employ propargyl alcohol as the coupling partner without any observation of any interference of the terminal alkyne. Selective oxidative coupling of a primary alcoholic functional group over secondary in the case of glycols and glycerols was also made possible using the developed catalyst system. To test the relevancy of Pd/Ag combined catalysis mixed Pd/Ag colloids were synthesized, characterized by TEM, XRD and XPS and applied to oxidative-esterification successfully.
- Sable, Vaibhav,Shah, Jagrut,Sharma, Anuja,Kapdi, Anant R.
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supporting information
p. 2639 - 2647
(2019/07/08)
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- Safe and Facile Access to Nonstabilized Diazoalkanes Using Continuous Flow Technology
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Despite the high synthetic potential of nonstabilized diazo compounds, their utilization has always been hampered by stability, toxicity, and safety issues. The present method opens up access to the most reactive nonstabilized diazoalkanes. Among diazo compounds, nonstabilized alkyl diazo compounds are the least represented because of their propensity to degrade during preparation. The continuous flow oxidation process of hydrazones on a silver oxide column afforded an output stream of base- and metal-free pure diazo solution in dichloromethane. Starting from innocuous ketones and aldehydes, this methodology allows the production of a broad range of unprecedented diazoalkanes compounds in excellent yields, while highlighting their synthetic potential and the possibility of safe large-scale diazo production.
- Rullière, Pauline,Benoit, Guillaume,Allouche, Emmanuelle M. D.,Charette, André B.
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p. 5777 - 5782
(2018/05/14)
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- Visible-Light-Promoted Activation of Unactivated C(sp3)-H Bonds and Their Selective Trifluoromethylthiolation
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Selective functionalization of ubiquitous C(sp3)-H bonds using visible light is a highly challenging yet desirable goal in organic synthesis. The development of such processes relies on both rational design and serendipitous discoveries from innovative tools such as screening technologies. Applying a mechanism-based screening strategy, we herein report photoredox-mediated hydrogen atom transfer catalysis for the selective activation of otherwise unactivated C(sp3)-H bonds, followed by their trifluoromethylthiolation, which has high potential as a late-stage functionalization tool. The generality of this method is exhibited through incorporation of the trifluoromethylthio group in a large number of C(sp3)-H bonds with high selectivity without the need for an excess of valuable substrate.
- Mukherjee, Satobhisha,Maji, Biplab,Tlahuext-Aca, Adrian,Glorius, Frank
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supporting information
p. 16200 - 16203
(2016/12/27)
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- Silver-mediated oxidative aliphatic C-H trifluoromethylthiolation
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The first example of a practical and direct trifluoromethylthiolation reaction of unactivated aliphatic C-H bonds employs a silver-based reagent. The reaction is operationally simple, scalable, and proceeds under aqueous conditions in air. Furthermore, its broad scope and good functional-group compatibility were demonstrated by applying this method to the selective trifluoromethylthiolation of natural products and natural-product derivatives.
- Guo, Shuo,Zhang, Xiaofei,Tang, Pingping
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supporting information
p. 4065 - 4069
(2015/03/30)
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- Solid-Phase Benzoylation of Phenols and Alcohols in Microwave Reactor: An Ecofriendly Protocol
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An efficient solid-phase benzoylation of phenols and alcohols was developed under microwave irradiation. A stoichiometric amount of benzoyl chloride was sufficient to carry out the reaction. This benzoylation features short reaction time, good yields, and easy workup procedures. Furthermore, the scope of the reaction was extended to prepare 3,5-dinitrobenzoyl derivatives of alcohols.
- Chakraborty, Suchandra,Saha, Ahana,Basu, Kaushik,Saha, Chandan
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supporting information
p. 2331 - 2343
(2015/10/12)
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- Generally applicable and efficient esterification of aldehydes with alcohols catalyzed by cyclopalladated ferrocenylimine
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The palladacycle-catalyzed esterification of a variety of aldehydes with alcohols was developed. This reaction allows formation of esters in moderate to excellent yields not only for various aldehydes but also alcohols. In addition, the esterification could proceed well under mild conditions with a low catalyst loading of 0.0625 mol%. Copyright
- Ma, Gaizhi,Leng, Yuting,Qiao, Huijie,Yang, Fan,Wang, Shiwei,Wu, Yangjie
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- A facile and efficient protocol for esterification and acetalization in a PEG1000-D(A)IL/toluene thermoregulated catalyst-media combined systems
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A novel efficient and recyclable temperature-dependent biphasic catalyst and reaction media combined system comprised of PEG-1000 linked dicationic acidic ionic liquid and toluene was developed and applied in esterification of aromatic acids and acetalization of aromatic aldehydes with good to excellent yields. This system is characteristic of temperature-dependent reversible biphasic property, simple and facile recyclability, high catalytic activity and extensive substrate and reaction adaptability.
- Wang, Yinglei,Zhi, Huizhen,Luo, Jun
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- Catalysis studies of macroreticular polystyrene cation-exchange resin with terminal perfluoroalkanesulfonic acids
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Macroreticular p-(ω-sulfonic-perfluoroalkylated) polystyrene (FPS) resin with the advantages of both sulfonic polystyrene (such as macroreticular Amberlyst-15) and perfluoroalkanesulfonic resin (such as superacidic Nafion NR50) has exhibited excellent catalytic selectivity and activity in cyclization of pseudoionone and condensation of indole. In this paper, FPS was characterized by XPS, nitrogen sorption technique, FESEM and Hammett indicator method, and employed as the solid acid catalyst in the esterification, acylation and alkylation reactions. The FPS resin showed better activity than commercial solid acid catalysts (Amberlyst-15 and Nafion NR50) owing to its high surface area and strong acidity close to superacidity.
- Lin, Zhenghuan,Guan, Chuanjin,Huang, Limei,Wang, Wen,Ling, Qidan,Zhao, Chengxue
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p. 261 - 266
(2013/07/27)
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- Synthesis of new oxidant N-chloroisonipecotamide and its oxidation kinetics on aromatic acetals
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The new oxidant N-chloroisonipecotamide (NCINA) is prepared by standard procedure and characterized. The formal redox potential, physical constant, elemental analysis and spectral characterization (IR, 1H-NMR and Mass spectrum) confirms the presence of nitrogen-halogen bond. It is found to be a mild and stable oxidant and formal redox potential of N-chloroisonipecotamide shows that it can be used as an effective source of positive halogen, like other existing oxidants. Oxidation of benzaldehyde di-n-alkyl acetals is carried out with new oxidant in acetonitrile medium. The reaction is first order with respect to NCINA and zero order with respect to acetals. The effect of isonipecotamide and acetonitrile is studied. Increase in ionic strength has marginal effect on the rate. A mechanism consistent with the observed kinetic results has been elucidated.
- Shenbagam,Mathiyalagan
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p. 747 - 752
(2013/11/06)
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- Kinetics and mechanism of oxidation of aromatic acetals by N-chloronicotinamide in acetonitrile medium
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An effort has been made to Introduce N-chloronicotinamide (NCN) as an oxidant to some aromatic acetals. The reaction shows total first order kinetics, zero order in [acetal] and first order in [NCN]. Increase in ionic strength has marginal effect on the rate while increase in dielectric constant of the medium decreases the rate. Further the rate is slightly decreased by the addition of nicotinamide. Arrhenius parameters and activation parameters are calculated. A mechanism consistent with the observation is proposed and an appropriate rate law is derived.
- Shenbagam,Mathiyalagan
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p. 1343 - 1346
(2013/02/22)
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- Hydrogen peroxide mediated efficient amidation and esterification of aldehydes: Scope and selectivity
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An efficient method for the amidation and esterification of aldehydes utilizing hydrogen peroxide as an oxidant has been developed. Cyclic amines and primary alcohols selectively reacted with aromatic aldehydes under mild conditions to yield the corresponding amides and esters.
- Tank, Rekha,Pathak, Uma,Vimal, Manorama,Bhattacharyya, Shubhankar,Pandey, Lokesh Kumar
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p. 3350 - 3354
(2012/01/06)
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- Polymer-supported ytterbium perfluorooctanesulfonate [Yb(OPf)3]: A recyclable catalyst for organic reactions
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Amberlyst A-21, a kind of well-known and cheap polymeric material, was treated with ytterbium perfluorooctanesulfonate [Yb(OPf)3] giving a reagent with a ytterbium loading of 1.34 (wt%). The polymer-supported fluorous ytterbium catalyses the highly efficient nitration, esterification, Fridel-Crafts acylation, and aldol condensation. The catalyst can be recovered by simple filtration and used again without a significant loss of catalytic activity. The protocol avoids the use of fluorous solvents during the reaction or workup, which are expensive and can leach in small amounts.
- Yi, Wen-Bin,Cai, Chun
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p. 524 - 528
(2008/12/22)
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- Bis(pentafluorophenyl) disulfide as a hydrogen abstractor and an electron acceptor from the resulting radical intermediate
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The pentafluorobenzenethiyl radical is an efficient hydrogen abstractor from an activated methylene or methine group and bis(pentafluorophenyl) disulfide is an efficient electron acceptor from the resulting radical intermediate. Thus benzyl-OTBS ether was easily converted into the corresponding pinacol, and 2-phenyl-1,3-dioxanes are converted into the monobenzoates of diols.
- Tada, Masaru,Katayama, Emi,Sakurai, Naoto,Murofushi, Keita
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- Selective sulfonylation of arenes and benzoylation of alcohols using lithium perchlorate as a catalyst under neutral conditions
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Sulfonylation of aromatics with p-toluenesulfonyl chloride and benzoylation of alcohols with benzoyl chloride using lithium perchlorate as a catalyst is described. The remarkable selectivity under neutral conditions is an attractive feature of this method.
- Bandgar,Kamble,Sadavarte,Uppalla
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p. 735 - 738
(2007/10/03)
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- Radical-chain redox rearrangement of cyclic benzylidene acetals to benzoate esters in the presence of thiols
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Cyclic benzylidene acetals derived from 1,2- and 1,3-diols undergo an efficient ring-opening redox rearrangement to give benzoate esters in the presence of a peroxide initiator and a thiol, which acts as a polarity-reversal catalyst to promote the radical-chain reaction.
- Roberts, Brian P.,Smits, Teika M.
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p. 137 - 140
(2007/10/03)
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- Linear free energy relationship and conformational effects on oxidation of aromatic acetals by pyridinium fluorochromate
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Kinetics of oxidation of aromatic acetals by pyridiniumfluorochromate (PFC) in aqueous acetic acid medium reveal that the reactions are second order, first order each in [acetal] and [PFC]. The presence of electron- withdrawing substituents in the benzene ring enhances the rate of oxidation while that of opposite one retards it. The small ρ value suggests a mechanism with little charge separation. The rate of oxidation depends on the nature of alkyl group and conformational effects.
- Ramakrishnan,Nambi
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p. 232 - 234
(2007/10/03)
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- A New Indirect Application of Aggregative Activation: Synthesis of Esters by Cobalt-Catalyzed Carbonylation of Aryl, Heterocyclic, and Vinyl Halides under Atmospheric Pressure
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Sun lamp illuminated alkoxycarbonylation of aryl, heteroaryl, and vinyl halides was performed under atmospheric pressure of CO in the presence of a cobalt catalyst in situ generated from Co(OAc)2.Illunination through a Pyrex flask was sufficient to catalyze the reaction.This process avoids the use of Co2(CO)8 and excess CH3I, which were required in the earlier procedure.A SRN1 mechanism is proposed.
- Marchal, Joel,Bodiguel, Jacques,Fort, Yves,Caubere, Paul
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p. 8336 - 8340
(2007/10/02)
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- Action of Lewis Acids on Aromatic Acetals
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Acetals of the type X.C6H4CH(OR)2, where R = Et, n-Bu and isoamyl, and X = H and CH3, react with antimony perchloride and ferric chloride in anhydrous 1,2-dichloroethane to give benzyl alkyl ether, alkyl benzoate, benzyl ester, α,β-unsaturated aldehyde, benzaldehyde and a small quantity of benzyl alcohol. p-Nitrobenzaldehyde di-n-butyl acetal gave only p-nitrobenzaldehyde and a trace of p-nitrobenzyl alcohol.The mechanism of the formation of benzyl alkyl ether is explained by a hydride ion transfer and that of α,β-unsaturated aldehyde by an aldol type of condensation.The aliphatic and aromatic aldehydes produced in the reaction could undergo Tischenko reaction in the presence of antimony or iron alkoxides to give the esters.
- Alphonse, I.,Arulraj, S. J.
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p. 820 - 822
(2007/10/02)
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- Rearrangement of Aromatic Acetals Over Solid Acid Catalysts
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The reactions of aromatic acetals (1a-6a) catalysed by aluminium phosphate (AP) yield the corresponding esters (b), ethers (c) and the parent aldehydes (d).Similar reactions over aluminium sulphate (AS) give only esters (b) and the aldehydes (d).Probable mechanisms have been suggested for the reactions.The catalysts have been characterized by various studies.The specific poisoning of the catalysts have been done with NH3 and CO2 and the product formation on the poisoned catalyst provides support to the suggested mechanisms.
- Xavier, N.,Arulraj, S. J.
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p. 519 - 522
(2007/10/02)
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- ANODIC OXIDATION OF COMPOUNDS HAVING BENZYLIC OR ALLYLIC CARBON AND α-CARBON TO HETERO ATOM USING N-HYDROXYPHTHALIMIDE AS A MEDIATOR
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Benzylic, allylic carbons and the carbon α to hetero atoms are electrochemically oxidized to the corresponding carbonyl group in the presence of N-hydroxyphthalimide under mild conditions.KEYWORDS - anodic oxidation; mediator; N-hydroxyphthalimide; benzylic carbon; allylic carbon; ether; sulfide; amide
- Masui, Masaichiro,Hara, Seijiro,Ueshima, Takahiro,Kawaguchi, Tetsuo,Ozaki, Shigeko
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p. 4209 - 4212
(2007/10/02)
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