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The alkylation of tetrazole and acetone under the catalysis of TfOH has been shown to be an efficient process with high levels of regioselective control. This protocol features simple and readily accessible starting materials, unique reaction mechanism, excellent compatibility with diverse functional groups. [Display omitted] • An effective process with high-level regioselective control: alkylation reaction of tetrazole and acetone catalyzed by TfOH. • The raw materials of this scheme are simple and easy to obtain, the reaction mechanism is unique, and it has good compatibility with different functional groups. The alkylation of tetrazole and acetone under the catalysis of TfOH has been shown to be an efficient process with high levels of regioselective control. This protocol features simple and readily accessible starting materials, unique reaction mechanism, excellent compatibility with diverse functional groups. [ABSTRACT FROM AUTHOR]

[Display omitted] • Secondary benzylic and allylic trichloroacetimidates can alkylate 1,2,3-triazoles. • With acid catalysis the alkylation of 1,2,3-triazoles is N2-selective (up to 91:9 N2:N1). • This method gives access to N2-alkyl 1,2,3-triazoles which are useful in medicinal/materials chemistry. A Brønsted acid catalyzed alkylation method for 1,2,3-triazoles is described using trichloroacetimidates as the electrophiles. These conditions were selective, with a strong preference of N2 alkylation product, often in high yield. The ratio of N2:N1 alkylation is sensitive to both the type of solvent used and the reaction concentration. The optimal results were obtained with a non-polar solvent at higher dilutions. Both 1,2,3-triazoles and 1,2,3-benzotriazoles could be alkylated under these conditions, providing access to N2 substituted 1,2,3-triazoles in good yields. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Employing chiral Co(III)-complex-templated Brønsted acids as catalysts. • The asymmetric intermolecular iodoacetalization of enol ethers was achieved. • This method provided an easy access to optically active 3-iodoacetal derivatives. • High yield and up to 83:17 er. Abstract The chiral Co(III)-complex-templated Brønsted acids were used as efficient bifunctional phase-transfer catalysts for the asymmetric intermolecular iodoacetalization of enol ethers, such as 3,4-dihydro-2H-pyran, 2,3-dihydrofuran, ethyl vinyl ether with alcohols and NIS, furnishing the 3-iodoacetals in high yield with up to 83:17 er. [ABSTRACT FROM AUTHOR]

Chiral imidodiphosphoric acids were employed as catalysts for the enantioselective α -chlorination of β -keto esters and amides using NCS as the chlorine source, providing a series of optically active products with good to high enantioselectivities (74–95% ee) and excellent yields (92–99%). This represents the first report of the Brønsted acid catalyzed enantioselective α -chlorination of cyclic β -keto derivatives. [ABSTRACT FROM AUTHOR]

[Display omitted] A thermodynamic-promoting diastereoselective synthesis of dispirooxindole-pyrrolizines was developed by a five-component reaction with a dual 1,3-dipolar cycloadditions process of non-stabilized azomethine ylides that includes the decarboxylation of glycine and α C H functionalization of generated pyrrolidines in situ. This process is a solid and versatile strategy for rapidly assembling fused pyrrolizines with two spirooxindoles bearing seven stereocenters. Homogeneous Brønsted acid catalysis and benign solvent in one-step reaction can be used to promote the green process, with by-products of CO 2 and H 2 O, and potentiating environmental tolerance. [ABSTRACT FROM AUTHOR]

Combined use of Tf 2 NH and In(OTf) 3 effectively promotes the cyclization of alk-5-ynyl ketones to cyclopent-1-enyl ketones at 30 °C. Single use of Tf 2 NH or In(OTf) 3 requires heating at 50 °C for efficient cyclization. The In(OTf) 3 -promoted reaction of certain alk-5-ynyl ketones gives cyclohept-2-enones mainly. [ABSTRACT FROM AUTHOR]

A novel synthesis of coumarin derivatives by Brønsted acid-mediated condensation and intramolecular cyclization of phenols and propiolic acids was reported. This transformation requires the use of TfOH in place of a conventional metal mediator, and it occurs under mild conditions and provides rapid access to coumarin derivatives in good yields. [ABSTRACT FROM AUTHOR]

A novel catalytic nucleophilic addition of olefins to α,β-unsaturated-γ-lactams has been developed with a cyclic N -acyliminium ion as a key intermediate. It provides an efficient approach to 5-alkenyl-2-pyrrolidinones from simple and readily available starting materials and the desired products could be obtained in moderate to good yields (23–85%). [ABSTRACT FROM AUTHOR]

Brønsted acid p -TsOH·H 2 O-catalyzed phenylselenenylation of α-oxo ketene dithioacetals was efficiently achieved by using N -phenylselenophthalimide ( N -PSP) as the phenylseleno reagent. The resultant selenated ketene dithioacetals reacted with styrene in the presence of the same acid to undergo PhSe group transfer, regioselectively affording Markovnikov-type PhSe-alkylated olefins. Their further transformation with phenylboronic acid, guanidine, and hydrazine offers a promising route to access S,Se-incorporated organic compounds. [ABSTRACT FROM AUTHOR]

Herein we report interesting reactivity of imidazole carbamate towards nucleophilic substitution with halide ions under Brønsted acidic conditions. Depending upon reaction conditions, halide ions could readily attack the carboxyl position and trigger decarboxylative alkyl halide formation. Alternatively, halide ions were also found to competitively undergo nucleophilic acyl substitution, which ultimately results in the generation of carbonate dimerization product. [ABSTRACT FROM AUTHOR]

[Display omitted] A facile Brønsted acid-promoted three-component reaction of 2-methoxythiophene, sulfinates and water at room temperature has been discovered. Under the mild conditions, a series of γ- mercapto -β- sulfonyl esters were obtained in moderate to good yields. The control experiments support the reaction mechanism involves in three processes: 1,5-H shift, Michael addition and ring opening in water. [ABSTRACT FROM AUTHOR]

Efficient Brønsted acid-catalyzed allylation of benzhydryl alcohols has been developed. The reaction occurs within 5 min in the presence of sub-stoichiometric amounts of HBF 4 ·OEt 2 to afford the desired products in good to excellent yields. A variety of functional groups were tolerated under the developed conditions including amides, aldehydes, hydroxyl and carboxylic acid. [ABSTRACT FROM AUTHOR]

A Brønsted acid promoted C sp 3 – H functionalization of 2-alkyl azaarenes with α-trifluoromethylated imino ester is described. A catalytic amount of triflic acid provided straightforward access to the corresponding trifluoromethylated amino esters via concomitant in situ one step N -alkyl deprotection. On further hydrolysis of ester, synthesis of quinoline derived unnatural trifluoromethylated amino acids has been achieved in a short and efficient manner. [ABSTRACT FROM AUTHOR]

Abstract: An efficient synthetic method to prepare highly substituted indenes in moderate to excellent yields that relies on Brønsted acid catalyzed Friedel–Crafts reaction of homoallylic alcohols under mild conditions is described. [Copyright &y& Elsevier]

Abstract: Developed a convenient and mild one pot synthesis of cyclopentenone derivatives using 1-acetyl-1-cyclohexene and wide range of aldehydes. Aromatic and heterocyclic aldehydes with electron donating and withdrawing groups were conveniently converted to the corresponding cyclopentenone derivatives. [Copyright &y& Elsevier]

Abstract: The first asymmetric reduction of ketimines with catecholborane employing an enantiopure N-triflyl phosphoramide as the organocatalyst has been developed. Five mole% of the catalyst provides the corresponding secondary amines in very good to almost quantitative yields and good enantioselectivities up to 86:14 e.r. under mild reaction conditions. [Copyright &y& Elsevier]

Abstract: New halogen-free Brønsted acidic deep eutectic solvents (DES) have been prepared by mixing new quaternary ammonium methanesulfonate salts with p-toluenesulfonic acid (PTSA). They have been used as dual solvent-catalyst for esterification of several carboxylic acids with different alcohols with a reagent molar ratio of 1:1. The method is mild, safe, and simple. Ease of recovery and reusability of DES with high activity makes this method efficient and eco-friendly. The tunability of DES properties, attained by changes in the cation, was performed in order to achieve various esters in good yields. [Copyright &y& Elsevier]

Abstract: An asymmetric cyclization of alkynols triggered addition of azlactones catalyzed by a combined catalyst system consisting of a chiral gold phosphate and a phosphoric acid produces conformationally restricted amino acid precursors bearing vicinal quaternary stereogenic centers in high levels of stereoselectivity. [Copyright &y& Elsevier]

Abstract: Homogeneous Pd(OCOCF3)2/(R)-C4-TunePhos has been successfully applied in the asymmetric hydrogenation of simple ketones activated by catalytic amount of Brønsted acid with up to 88% ee. [Copyright &y& Elsevier]

Abstract: The synthesis of tetrahydroisoquinolines and tetrahydro-β-carbolines, using the Pictet–Spengler reaction, was carried out in the presence of a catalytic amount of o-benzenedisulfonimide, which worked as a Brønsted acid organocatalyst. The reaction conditions were mild and green and good target product yields were achieved. The catalyst was easily recovered and purified, ready to be used in further reactions with economic and ecological advantages. [ABSTRACT FROM AUTHOR]

A convenient and efficient organocatalytic procedure for the selective cyclization of 1,3-diketones to give aromatic substituted 4 H -chromen-4-ones under mild reaction conditions using N -triflyl phosphoramide is described. Application of the described conditions is presented in a formal synthesis of ( S )-flavanone. [ABSTRACT FROM AUTHOR]

In this study, anthracenes were efficiently synthesized from o -alkynyldiarylmethane using a novel method that exploits the synergistic effect between Bi(OTf) 3 as the catalyst, and trifluoroacetic acid (TFA). Through this reaction, we achieved the rapid and efficient synthesis of anthracenes bearing various functional groups under mild conditions. [ABSTRACT FROM AUTHOR]

Abstract: Perfluorooctanesulfonic acid (PFOSA), Brønsted acid-surfactant-combined catalyst, efficiently catalyzes the Pictet–Spengler reactions of β-arylethyl carbamate derivatives with aldehydes in water. The present reaction is accelerated by the addition of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). [Copyright &y& Elsevier]

Abstract: We report herein Brønsted acid TfOH-mediated reactions of 2-(arylmethylene)cyclopropylcarbinols with acetonitrile to give the corresponding ring-enlarged N-(3-arylmethylidenecyclobutyl)acetamides in moderate to good yields under mild conditions. A plausible mechanism is proposed on the basis of previous investigations. [Copyright &y& Elsevier]

Abstract: Ring opening reactions of 2-cyclohexylidene-3,3-dimethylcyclopropanone acetal (1) are readily induced by treatment of hydrogen chloride in various solvents. Bond cleavage takes place at the C1–C2 or C2–C3 bond, and the ratio of C1–C2/C2–C3 cleavages changes from >99/1 to <1/99 depending on the solvent. The two modes of bond cleavage must be initiated by protonations at the carbon–carbon double bond and the acetal oxygen, respectively. The regioselectivity can be rationalized by the rate-determining protonation at carbon and the equilibrium protonation at oxygen. [Copyright &y& Elsevier]

Abstract: An environmentally friendly and highly efficient procedure for the preparation of substituted quinoline derivatives was developed by a simple Friedländer reaction of 2-aminoarylketone or 2-aminoarylaldehyde with carbonyl compounds in the presence of hydrochloric acid utilizing water as the solvent. [Copyright &y& Elsevier]

Functionalized quinolizidin-4-ones and indolizidin-3-ones were synthesized from mixed N,O-acetals with a terminal alkyne unit and nucleophiles with two reactive sites by a gold(I)/Brønsted acid relay catalysis with 40–90% yield. The reactions are proposed to proceed through gold-catalyzed carboalkoxylation of the alkynes with the internal mixed N,O-acetals, giving the corresponding cyclic enols, which are transformed to spirocyclic compounds by a Brønsted acid catalyst. The latter spirocyclization process occurs under thermodynamic control, providing polycyclic quinolizidin-4-one and indolizidin-3-one derivatives diastereoselectively. [ABSTRACT FROM AUTHOR]

Silica gel readily adsorbs strong Brønsted acids such as bis(trifluoromethanesulfonyl) imide (Tf 2 NH) to afford a heterogeneous supported catalyst that enables various acid-promoted reactions. The catalyst was recovered by means of easy filtration and reused for three successive runs. In addition, various acid-promoted reactions proceed smoothly with the reaction column system packed within silica gel-supported Brønsted acid. [ABSTRACT FROM AUTHOR]

The H–D exchange of aromatic amines and amides, including pharmaceutically relevant compounds such as acetaminophen and diclofenac, was investigated using CF 3 COOD as both the sole reaction solvent and source of deuterium label. The described method is amenable to efficient deuterium incorporation for a wide variety of substrates possessing both electron-donating and electron-withdrawing substituents. Best results were seen with less basic anilines and highly activated acetanilides, reflecting the likelihood of different mechanistic pathways. [ABSTRACT FROM AUTHOR]

α-Aminonitriles have been synthesized by a Strecker synthesis from aldehydes and ketones under mild catalytic, metal-free conditions. Aromatic aldehydes (1 equiv) were reacted with aromatic and 1° or 2° aliphatic amines (1 equiv) in EtOH containing 3mol% of NH4Cl to give high yields of α-aminonitriles. An alternative to adding NH4Cl as a catalyst involved the use of excess TMSCN (1 equiv) and to promote the process. The reaction was also successful under microwave conditions using excess TMSCN with no solvent. Ketones similarly reacted with aromatic amines and excess TMSCN under conventional and microwave heating, but 30mol% of added NH4Cl was required for optimum conversion. [ABSTRACT FROM AUTHOR]

• Brønsted acid-catalyzed friedel-crafts-type alkylation. • Various diarylmethane derivatives were isolated in moderate to high yields. • β,β-diaryl substituted γ-butyrolactone could be synthesized. An efficient Brønsted acid-catalyzed Friedel-Crafts-type alkylation of arenes with α-aryl diazoacetates has been developed. This protocol enables effective access to various highly functionalized diarylmethane derivatives in moderate to high yields. Moreover, the product of selected diaryl acetate could be transformed to β, β-diaryl substituted γ-butyrolactone. [ABSTRACT FROM AUTHOR]

Abstract: The hydroamination of various substituted vinyl arenes with benzenesulfonamide was explored using an NHC-amidate-alkoxide palladium catalyst in conjunction with p-TsOH. Utilizing halide-substituted and electron-rich vinyl arenes, this methodology selectively furnished the cross-coupled hydroamination products in moderate to excellent yields in a Markovnikov fashion while greatly reducing undesired acid-catalyzed homocoupling of the vinyl arenes. Electron-rich vinyl arenes typically required milder conditions than electron-poor ones. While most effective for para-substituted substrates, the catalyst system also furnished the desired products from ortho- and meta-substituted vinyl arenes with high chemoselectivities. [Copyright &y& Elsevier]

Abstract: An organocatalytic asymmetric tandem 1,5-hydride transfer/ring closing reaction of o-aminobenzoketones with anilines to give cyclic aminals in fairly good diastereo- and enantioselectivities. [Copyright &y& Elsevier]

Abstract: The reaction of helical quinone with alcohols in the presence of Brønsted acid such as para-toluenesulfonic acid (pTSA) or HCl proceeded smoothly to produce the corresponding alkoxy substituted oxa[9]helicenes in good yields. [Copyright &y& Elsevier]

Abstract: A simple and convenient Brønsted acid (HNO3)-catalyzed tandem reaction of α-ketoesters with primary or secondary aromatic amines for the synthesis of polysubstituted 1,2-dihydroquinolines has been developed via a tandem process, which has the advantages of ready availability of catalyst, operation simplicity, atom efficiency as well as low toxicity. In particular, tricyclic dihydroquinolines, generally prepared with multi-processes, could also be constructed in this one-pot procedure. [Copyright &y& Elsevier]

Abstract: The synthesis of quinolines via Friedländer annulation was carried out in the presence of catalytic amount of o-benzenedisulfonimide as Brønsted acid organocatalyst; the reaction conditions were mild and the yields of the target products were good. The organocatalyst was easily recovered and purified, ready to be used in further reactions. [Copyright &y& Elsevier]

Abstract: An unusual bicyclic hydroxamate resulted from C–O bond cleavage of acylnitroso hetero-Diels–Alder cycloadducts when treated with catalytic Brønsted acids under anhydrous conditions. Similarly, the formation of a nitrone was observed using one equivalent of triflic acid. [Copyright &y& Elsevier]

Abstract: The bicyclo[4.3.0]nonane ring system of the pinguisane-type sesquiterpenoid natural products, including the vicinal quaternary stereocentres, has been synthesised as a single enantiomer via a novel Brønsted acid promoted transannular alkylation of an enol with an unactivated alkene. [Copyright &y& Elsevier]