A convenient synthesis of some α-oxoketene-N,S- and N,N-acetals

Some α-oxoketene-N,S- and N,N-acetals were selectively synthesized in good to excellent yields by the reaction of 1,1-dimethoxy-4,4-di(methylthio)-3-buten-2-one with primary and secondary amines under moderate conditions. Secondary amines in reaction with α-oxoketene dithioacetal yielded double-substitution products exclusively, whereas primary amines under the same conditions yielded the mono-substituted products as exclusive or main products.     

Efficient oxidative N-dealkylative addition of trialkylamines to dimethyl acetylenedicarboxylate using BrCCl3 as the terminal oxidant

Herein we present a continuous improvement of visible-light mediated N-dealkylative addition of tertiary amines to dimethyl acetylenedicarboxylates (DMAD) using alkyl halogenides as external oxidants together with base additives. This method is highlighted by excellent tolerance with various tertiary amines and good to excellent yields in short reaction time under mild conditions.     

Selective C-C bonds formation,N-alkylation and benzo[d]imidazoles synthesis by a recyclable zinc composite

Earth abundant metals are much less expensive, promising, valuable metals and could be served as catalysts for the borrowing hydrogen reaction, dehydrogenation and heterocycles synthesis, instead of noble metals. The uniformly dispersed zinc composites were designed, synthesized and carefully characterized by means of XPS, EDS, TEM and XRD. The resulting zinc composite showed good catalytic activity for the N-alkylation of amines with amines, ketones with alcohols in water under base-free conditions, while unsaturated carbonyl compounds could also be synthesized by tuning the reaction conditions. Importantly, it was the first time to realize the synthesis of 2-aryl-1H-benzo[d]imidazole derivatives by using this zinc composite under green conditions. Meanwhile, this zinc catalyst could be easily recovered and reused for at least five times.     

Access to 1,2,3-triazole-fused isoindolines via an unexpected Lewis acid catalyzed cyclization reaction

An unexpected cyclization reaction of N-sulfonyl 1,2,3-triazoles carrying the electron-deficient alkenes with amines under the catalysis of Lewis acid has been accomplished. This strategy involves the removal of the sulfonyl group and further intramolecular 1,4-addition, providing a series of 1,2,3-triazole-fused isoindoline compounds in good yields under the mild conditions.     

Metal-free N-iodosuccinimide-catalyzed mild oxidative C-H bond amination of benzoxazoles

A facile, efficient, and mild protocol for the synthesis of aminobenzoxazoles has been developed using direct oxidative C-H bond amination of benzoxazoles with secondary or primary amines. The reaction was performed using catalytic amount of N-iodosuccinimide and aqueous hydrogen peroxide as a green oxidant and in the absence of transition metals. Reaction proceeds smoothly at ambient temperature and requires shorter reaction time to furnish excellent yield of the desired products. Various cyclic, acyclic, and functionalized aliphatic amines were well tolerated under optimized reaction conditions and provided good to excellent yield of the respective aminobenzoxazoles.     

A microwave-enhanced, solventless Mannich condensation of terminal alkynes and secondary amines with para-formaldehyde on cuprous iodide doped alumina

A microwave-enhanced, solventless Mannich condensation of terminal alkynes and secondary amines with para-formaldehyde on cuprous iodide doped alumina has been developed. β-Aminoalkynes are generated in good yields. The reaction can be extended to include a cyclization, which affords 2-substituted benzo[b]furans. The chemoselectivity of the reaction indicates that terminal alkynes are much more reactive than enolizable ketones under the reaction conditions.     

Reactions of chloroalkyl-gem-dichlorocyclopropanes with amines

N-Alkylation of primary and secondary amines with monochloroalkyl-gem-dichlorocyclopropanes under conditions of thermal and microwave heating results in the corresponding amino-gem-dichlorocyclopropanes. With microwave irradiation heating, the reaction time has been decreased to 1 h, the yields of the amines containing gem-dichlorocyclopropane moiety being the same. Formation of the bicyclic amine in reaction of cis-2,3-dichloromethyl-gem-dichlorocyclopropane with primary amines under conditions of phasetransfer catalysis has been studied.     

Saccharin sulfonic acid catalyzed N-Boc protection of amines and formation of tert-butyl ethers from alcohols

Saccharin sulfonic acid (SaSA), as a stable reagent is easily prepared by the reaction of saccharin with neat chlorosulfonic acid at room temperature. This compound is able to catalyze conversion of amines to their corresponding N-Boc protected amines with (Boc)₂O. Alcohols were also converted to their corresponding tert-butyl ethers. All reactions took place under mild conditions giving the desired products in good to high yields.     

ZnO nanoparticles catalyzed efficient one-pot three-component synthesis of 2,3-disubstituted quinalolin-4(1H)-ones under solvent-free conditions

ZnO nanoparticles were prepared and applied as a favorable catalyst in three-component one-pot cyclocondensation reaction of isatoic anhydride with amines and aldehydes to afford the corresponding 2,3-disubstituted quinalolin-4(1H)-ones in good yields. Reactions occurred under solvent-free conditions in high atom economy.     

Metal-free oxidative amide formation with N-hydroxysuccinimide and hypervalent iodine reagents

An oxidative amide formation using N-hydroxysuccinimide and hypervalent iodine reagents was developed. The method enables a wide range of aldehydes and amines to be coupled under mild reaction conditions providing amide in good to excellent yield. The radical species in the reaction mixture was observed for the first time using ESR measurement, and along with other mechanistic investigations, a plausible mechanism of the reaction was proposed.     

Fluorous electrophilic scavengers for solution-phase parallel synthesis

A fluorous isatoic anhydride and isocyanate are synthesized and used as scavengers for amines in solution-phase parallel synthesis of urea, thiourea, and β-hydroxyamine analogs. The resulting fluorous derivatives are readily separated from the reaction mixture by solid-phase extractions (SPE) over FluoroFlash™ cartridges to give products with good purity. The SPE cartridges can be reused.     

Catalyst-free synthesis of functionalized dihydro-2-oxypyrroles by the reaction of enaminones and N,N′-bis(phenylmethylidene)phenylmethane

A catalyst-free and convenient approach for the preparation of substituted dihydro-2-oxypyrrole is described. This three-component reaction between primary amines, dialkyl acetylenedicarboxylate, and N,N′-bis(phenylmethylidene)phenylmethane proceeds in MeOH under reflux conditions in good to excellent yields.     

A four-component, one-pot synthesis of highly substituted 1,4-dihydro-1,8-naphthyridine-3-carboxamides

A new, one-pot, four-component reaction for the synthesis of a novel class of highly substituted 1,4-dihydro-1,8-naphthyridine-3-carboxamide derivatives starting from readily available inputs including aliphatic or aromatic amines, diketene, aromatic aldehydes, and 2-aminopyridines in the presence of a catalytic amount of p-toluenesulfonic acid under mild reaction conditions and in good yields at ambient temperature is described.     

Fluorous scavenger for parallel preparation of tertiary sulfonamides leading to secondary amines

Alkylation of secondary sulfonamides by alkyl halides or alcohols (Mitsunobu reaction) is an efficient method for secondary amines preparation. However, its application to parallel chemistry is often difficult due to partial reaction. In this Letter, we propose a fluorous technique to bypass this problem. Thus, o-nitrobenzenesulfonamides were prepared and alkylated in parallel (Fukuyama method) with various alkyl halides or alcohols. Depending on the nature of the alkyl halide or alcohol, this step remained incomplete. A reactive fluorous alkyl iodide was then used to trap the unreacted sulfonamide allowing for a rapid and efficient fluorous solid-phase extraction (FSPE). Some examples of the isolated tertiary sulfonamides were converted in parallel to the corresponding secondary amines with good purity.     

Microwave assisted,sequential two-step,one-pot synthesis of novel imidazo[1,2-a]pyrimidine containing tri/tetrasubstituted imidazole derivatives

A series of novel imidazo[1,2- a ]pyrimidine containing tri/tetrasubstituted imidazole derivatives (1-10) has been synthesized via sequential two-step, one-pot, multicomponent reaction using imidazo[1,2- a ]pyrimidine-2-carbaldehyde, benzil, primary amines, and ammonium acetate catalyzed by p -toluenesulfonic acid under microwave-assisted conditions. The results showed that target compounds can be obtained from a wide range of primary amines bearing different functional groups with moderate to good yields (46%-80%) under optimum reaction conditions. This method provides a green protocol for imidazo[1,2- a ]pyrimidine containing tri/tetrasubstituted imidazole derivatives due to ethyl alcohol as a green solvent, microwave irradiation as a greener heating method and one-pot multicomponent reaction as a green technique. The synthesized compounds have been elucidated using various spectroscopic tools such as FT-IR, ¹H NMR, ¹³ C NMR, and MS.     

An Exceedingly Mild,Green Synthesis of Substituted N‐3‐diaryl‐1,8‐naphthyridin‐2‐amine Derivatives and Their Antimicrobial Activity

An exceedingly and highly efficient procedure has been described for the synthesis of substituted N‐3‐diaryl‐1,8‐naphthyridin‐2‐amines by the reaction of 2‐chloro‐3‐aryl‐1,8‐naphthyridines with various anilines in the presence of N‐methyl‐2‐pyrrolidone and K₂CO₃ under thermal green solvent‐free conditions. The significant features of this green reaction include very good yields in purity, simple experimental, short reaction time, easy workability, and avoidance of toxic solvents. All synthesized compounds have been evaluated for their antibacterial activity.     

A new and high yielding synthesis of unstable pyrroles via a modified Clauson-Kaas reaction

An investigation of the reaction requirements to effect the Clauson-Kaas pyrrole synthesis led to the formulation of a new procedure that avoids the contact of pyrroles to heat or strongly acidic conditions that cause decomposition of the desired products. The procedure involves mild hydrolysis of 2,5-dimethoxytetrahydrofuran in water to the activated species 2,5-dihydroxytetrahydrofuran that reacts with primary amines in an acetate buffer at room temperature to give N-substituted pyrroles in high yield. In the case of chiral amines, pyrrole formation proceeds with no detectable epimerisation. Acid- or heat-sensitive pyrroles are also obtained in high yield and purity.     

Asymmetric synthesis of α-amino aldehydes from sulfinimine (N-sulfinyl imine)-derived α-amino 1,3-dithianes. Formal synthesis of (−)-2,3-trans-3,4-cis-dihydroxyproline

Hydrolysis of sulfinimine-derived N-sulfinyl α-amino 1,3-dithianes with aqueous 1,3-dibromo-5,5-dimethylhydantoin affords the corresponding N-tosyl α-amino aldehydes in good yield and high enantiomeric purity. These aldehydes can be reduced to amino alcohols and undergo the Wittig reaction to give allylic amines without epimerization. The utility of this methodology is illustrated in a formal synthesis of (−)-2,3-trans-3,4-cis-dihydroxyproline.     

Phosphomolybdic acid-catalyzed efficient one-pot three-component aza-Diels-Alder reactions under solvent-free conditions: a facile synthesis of trans-fused pyrano- and furanotetrahydroquinolines

trans-Fused pyrano- and furanotetrahydroquinoline derivatives have been synthesized via a one-pot three-component aza-Diels-Alder reaction of aryl imines formed in situ from aromatic amines and arylaldehydes with cyclic enol ethers,such as 3,4-dihydro-2H-pyran and 2,3-dihydrofuran,in the presence of 1 mol % of phosphomolybdic acid under solvent-free conditions at room temperature in good to excellent yields.     

Efficient synthetic protocol for substituted guanidines via copper(I)-mediated intermolecular amination of isothiourea derivatives

Amination of S-methyl-N,N′-bis-Boc-isothiourea with either primary or sterically hindered secondary amines promoted by copper(I) chloride and K₂CO₃ gave N,N′-bis-Boc protected guanidines in good to excellent yields under mild reaction conditions.