Convenient and simple synthesis of 2-aminothiazoles by the reaction of α-halo ketone carbonyls with ammonium thiocyanate in the presence of N-methylimidazole

Substituted 2-aminothiazole derivatives were obtained as a result of N-methylimidazole catalyzed cyclization of α-halo ketone carbonyls with ammonium thiocyanate in water-alcoholic media. The generality of the method has been demonstrated by screening a series of aromatic/heteroaromatic/aliphatic α-halo ketones, α-halo β-diketones, and α-halo β-ketoesters. The developed method is simple, mild, and general route for the preparation of diversely functionalized 2-aminothiazoles in good to moderate yields from readily available starting materials.     

Application of N-halo reagents in organic synthesis

This review article summarizes published data on the application of N-halo reagents (such as N-halo amines, N-halo amides and/or imides, N-halo sulfonamides and/or imides, and etc.) in various organic functional group transformations such as: oxidation reactions, deprotection and protection of different functional groups, halogenation of saturated and unsaturated compounds, acylation of alcohols, phenols, amines or thiols, epoxidation of alkenes, aziridination and etc. The main purpose of writing this review is encouraging of active researchers interested to this field for the synthesis of new N-halo reagents specially with different halogens and applications of these new N-halo reagents in organic reactions or finding more and more applications of existing N-halo reagents in organic synthesis.     

Amberlyst-15-promoted efficient 2-halogenation of 1,3-keto-esters and cyclic ketones using N-halosuccinimides

A simple and rapid process has been developed for the α-monohalogenation of 1,3-keto-esters with N-halosuccinimides catalyzed by Amberlyst-15^® at room temperature to produce the corresponding 2-halo 1,3-keto-esters in high yields. This protocol also extended to α-halogenation of cyclic ketones.     

N,N′,N″-Tri-Boc-guanidine (TBG): a common starting material for both N-alkyl guanidines and amidinoureas

In this Letter, we describe the unexpected reaction pattern of N,N′N″-tri-Boc-guanidine (TBG) with amines at room temperature and under reflux conditions affording N-substituted guanidines and amidinoureas, potentially important compounds with extensive applications in medicinal chemistry. This investigation shows that TBG is an excellent, readily available common starting material for the synthesis of various N-alkyl guanidines as well as N-alkyl-N′-substituted amidinoureas by simply manipulating the reaction conditions.     

Studies into the generation and Diels-Alder reactions of 7,8-quinolyne with furan dienes

Reaction of an appropriate ortho-halo tosylate precursor with organolithium reagents provides the first conclusive route to the intermediate, 7,8-quinolyne. The transient existence of this hetaryne was confirmed by Diels-Alder reactions with furan derivatives that provide endoxide adducts. Chemical induced rearrangement of these adducts allows entry to key compounds of 10-hydroxy[h]benzoquinoline and its 7-substituted derivatives in modest yields.     

Acyclic tertiary diamines and 1,4,7,10-tetraazacyclododecane with fluorine-containing β-diketones: Leading to low melting ionic adducts

N,N,N′,N′-Tetramethylmethanediamine (1a), N,N,N′,N′-tetramethylethanediamine (1b), N,N,N′,N′-tetramethyl-1,3-propanediamine (1c), and N,N,N′,N′-tetramethyl-1,6-hexanediamine (1d) were reacted at 25 °C with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (2a), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedione (2b), 2-thenoyltrifluoroacetone (2c), and 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione (2d) to form the ionic adducts 3-18. 1,4,7,10-Tetraazacyclododecane (1e) reacted at 25 °C with β-diketones (2a-d) and 1,1,1-trifluoro-2,4-pentanedione (2e) to give ionic solids 19-23 in good yields. Some of the products are liquid at 25 °C and are thermally stable over long liquid ranges as determined by thermal gravimetric analyses. Single-crystal X-ray structure determinations show that compounds 9 and 21 crystallize in the monoclinic space groups P2(1)/c and P2(1)/n, respectively. All the new compounds were characterized by ¹H, ¹⁹F and ¹³C NMR, electrospray MS and/or elemental analyses.     

N-tert-Butyl-N-chlorocyanamide: a new reagent for the efficient preparation of gem-chloronitroso compounds

A new reagent for the efficient preparation of gem-chloronitroso compounds has been developed. The reaction of ketoximes with N-tert-butyl-N-chlorocyanamide takes place instantaneously in carbon tetrachloride at room temperature with excellent yields under mild conditions.     

A practical approach to non-natural or N-unsubstituted α-arylglycine derivatives: Hf(OTf)4-doped Me3SiCl system-catalyzed aminomethylation of electron-rich arenes with a new type of N,O-acetal

The authors have demonstrated the Hf(OTf)₄-doped Me₃SiCl system-catalyzed aminomethylation of electron-rich aromatic compounds, such as indoles and anilines, with new types of N,O-acetals having a variety of functional groups, such as cyano, ester, bis(trimethylsilyl)amino, diallylamino, and cyclic amino moieties, for the preparation of non-natural aromatic amino acid derivatives. Aminomethylation using an N,O-acetal with a bis(trimethylsilyl)amino group was particularly successful in the direct preparation of an N-unsubstituted α-indolylglycine derivative, which required only a standard aqueous workup.     

Evaluation of vacuum microwave-assisted extraction technique for the extraction of antioxidants from plant samples

In the present work, vacuum microwave-assisted extraction (VMAE) was to perform microwave-assisted extraction in vacuum. Two well-known antioxidants, vitamin C from guava and green pepper, and vitamin E (α-tocopherol and γ-tocopherol) from soybean and tea leaves, which were easy to be oxidized, were chosen as representative target compounds for the evaluation of VMAE. The extraction yields of vitamin C, α-tocopherol and γ-tocopherol in VMAE and those in MAE performed in atmosphere (air-MAE) were compared and the effects of extraction time, extraction temperature and sample matrix were studied. Moreover, the effects of the oxygen and subpressure invacuo were also discussed via performed MAE in N₂ atmosphere (N₂-MAE). The extraction yields of vitamin C, α-tocopherol and γ-tocopherol in VMAE were higher than that in air-MAE, 35% increments of vitamin C from green pepper, 22% increments of α-tocopherol and 47% increments of γ-tocopherol from tea leaves were obtained, respectively. The comparable increased extraction yields of vitamin C, α-tocopherol and γ-tocopherol in N₂-MAE to that in air-MAE confirmed that oxygen in system was the crucial factor for the oxidation of vitamin C and vitamin E, VMAE was beneficial for the extraction of these oxygen-sensitive compounds. In addition, the subpressure invacuo in the VMAE system also showed positive affect on the extraction yields. On the basis of preventing oxidation and improving extraction efficiency of target compounds because of less oxygen and subpressure invacuo in the extraction system, VMAE has good potential for the extraction of oxygen-sensitive and thermosensitive compounds from plant samples.     

Vinylogous N,N-dimethylaminomethylenation of 3-[(1-substituted)ethylidene]-oxindoles with N,N-dimethylformamide dimethylacetal

An efficient stereoselective synthesis of various 3-(3-dimethylaminoprop-2-enylidene)oxindoles has been disclosed. The compounds were synthesized via a vinylogous N,N-dimethylaminomethylenation at the γ-position of 3-[(1-substituted)ethylidene]oxindoles with DMF-DMA.     

A novel method of synthesis of 1,2-diketones from 1,2-diols using N-bromosuccinimide

A simple and convenient procedure is reported for the synthesis of benzils and aliphatic 1,2-diketones of cyclic and open chain compounds from corresponding hydrobenzoins and 1,2-diols by refluxing with N-bromosuccinimide in carbon tetrachloride in presence or absence of pyridine.     

First straightforward synthesis of 2,4-disubstituted benz[g]isoquinoline-3,5,10(2H)-triones, 1,2,3,5-substituted naphtho[3,2,1-de]isoquinoline-4,7-diones, and 6-substituted benzo[h]pyrido[3,4,5-kl]-1,2,3,4-tetrahydroacridine-5,8-diones

Structural modifications to the benz[g]isoquinoline skeleton of N-substituted benz[g]isoquinoline-3,5,10(2H)-triones were envisaged in order to make future SAR studies possible for this type of bioactive compounds. Several N-substituted benz[g]isoquinoline-3,5,10(2H)-triones were converted to novel 2,4-substituted benz[g]isoquinoline-3,5,10(2H)-triones, new tetracyclic 1,2,3,5-substituted naphtho[3,2,1-de]isoquinoline-4,7-diones, and 6-substituted benzo[h]pyrido[3,4,5-kl]-1,2,3,4-tetrahydroacridine-5,8-diones. All the synthesized target compounds represent new heterocyclic systems, which were previously undescribed in the literature.     

Synthesis, characterization and intercalation property of layered zirconium benzylamino-N,N-dimethylphosphonate phosphate materials

Layered zirconium benzylamino-N,N-dimethylphosphonate phosphate (ZBMPA) was prepared by the reaction of zirconyl chloride with benzylamino-N,N-dimethylphosphonic acid (H₂BMPA) and phosphoric acid in the presence of hydrofluoric acid. The intercalation of n-alkylamines (n-butylamine, n-heptylamine and n-decylamine) into ZBMPA was primarily investigated at room temperature. These materials were characterized by elemental analysis, ICP, XRD, SEM, FT-IR, Raman spectra, TG and DSC. The composition of ZBMPA is Zr(HPO₄)(C₆H₅CH₂N(CH₂PO₃)₂)_0.5 · 2.0H₂O. The interlayer distance of ZBMPA, n-butylamine, n-heptylamine and n-decylamine intercalation compounds is 2.03, 2.58, 2.52 and 3.17 nm, respectively. ZBMPA and the n-alkylamine intercalation compounds are different in the morphology and vibration spectra. Thermogravimetries of all materials obtained reveal three step mass losses at temperatures of up to 1000 °C. These results indicate that n-alkylamines are intercalated into the galleries of host ZBMPA.     

‘Push-Pull’ and spirobicyclic structures by reacting N-methyl cyclic ketene-N,X (X=S, O)-acetals with isocyanates and isothiocyanates

Nucleophilic N-methyl cyclic ketene-N,X (X=S, O)-acetals can react with electrophilic aryl isocyanates and aryl isothiocyanates to form ‘push-pull’ mono-adducts, di-adducts and spirobicyclic 6/5 ring compounds.     

Further studies of tetrakis(N,N′-dialkylbenzamidinato)diruthenium(III) chloro and alkynyl compounds: molecular engineering of metallayne monomers

Three diruthenium(III) compounds Ru₂(L)₄Cl₂, where L is mMeODMBA (N,N′-dimethyl-3-methoxybenzamidinate, 1a), DiMeODMBA (N,N′-dimethyl-3,5-dimethoxy benzamidinate, 1b), or DEBA (N,N′-diethylbenzamidinate, 1c), were prepared from the reactions between Ru₂(OAc)₄Cl and respective HL under reflux conditions. Metathesis reactions between 1 and LiC₂Y resulted in bis-alkynyl derivatives Ru₂(L)₄(C₂Y)₂ [Y=Ph (2), SiMe₃ (3), SiⁱPr₃ (4) and C₂SiMe₃ (5)]. The parent compounds 1 are paramagnetic (S=1), while bis-alkynyl derivatives 2-5 are diamagnetic and display well-solved ¹H- and ¹³C-NMR spectra. Molecular structures of compounds 1b, 1c, 2c, 3c and 4b were established through single crystal X-ray diffraction studies, which revealed RuRu bond lengths of ca. 2.32 Å for parent compounds 1 and 2.45 Å for bis-alkynyl derivatives. Cyclic voltammograms of all compounds feature three one-electron couples: an oxidation and two reductions, while the reversibility of observed couples depends on the nature of axial ligands.     

Selective N-debenzylation of amides with p-TsOH

N-Benzylamides were debenzylated efficiently with 4 equiv. of p-TsOH in refluxing toluene. Good to quantitative yields of the desired primary amides were obtained within 2-4 h from a wide variety of N-2,4-dimethoxybenzylamides. N-4-Methoxylbenzyl amides and N-benzylamides were also debenzylated cleanly. In the case of N-2,4-dimethoxylbenzylamides, selective N-debenzylation was possible in the presence of N-Fmoc, N-t-BOC or N-trityl-protection. Protected amino acid amides survived these conditions without any detectable epimerization.     

Reactivity of azafulvenium methides derived from pyrrolo[1,2-c]thiazole-2,2-dioxides: synthesis of functionalised pyrroles

Extrusion of sulfur dioxide from pyrrolo[1,2-c]thiazole-2,2-dioxides led to the synthesis of functionalised pyrroles via the generation of 1-azafulvenium methides. Sealed tube reaction conditions allowed the synthesis of N- and C-vinylpyrroles whereas from FVP methyl 1,3-dimethyl-5-oxo-5H-pyrrolizine-2-carboxylate and 4-oxo-1,4-dihydro-1-aza-benzo[f]azulene-3-carboxylates were obtained. These last compounds could also be obtained from the FVP of the N- and C-vinylpyrroles.     

Synthesis of chiral 2,2′-dipyridylamines and their use in the copper-catalyzed asymmetric allylic oxidation of cyclohexene

Chiral dipyridylamines have been synthesized by N-arylation reactions, and the applicability of those compounds to the copper-catalyzed asymmetric allylic oxidation of cyclohexene was demonstrated.     

Experimental and theoretical study of the structure of N,N-dimethyl-4-nitroaniline derivatives as model compounds for non-linear optical organic materials

Molecular and crystal structure of a series of derivatives of N,N-dimethyl-4-nitroaniline has been studied by both X-ray diffraction method and high-level ab initio calculations. According to these data, the dimethylamino groups were found to have a trigonal-pyramidal configuration and are considerably turned with respect to the ring plane in all molecules having a substituent in the ortho-position; on the contrary, this group is planar in the meta-substituted molecules. Topological analysis of the electron density function for all molecules studied within the framework of Bader's ‘atoms in molecules’ (AIM) theory revealed that introduction of a substituent into the ortho- or meta-position of the ring results in increasing of the contribution of the resonance forms different from the quinoid one. Contribution of the latter form is predominant for the structure of N,N-dimethyl-4-nitroaniline (1). Topological analysis of the electron density distribution was used to explain a decreasing of the molecular hyperpolarisabilites of the ortho- and meta-substituted compounds as compared with those for 1.     

Synthesis of tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone

A general strategy for the assembly of previously unknown tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone is described. The strategy involves N,N-bis(siloxy)enamines as key intermediates. The latter are accessible by double silylation of alkylnitro compounds. Nickel(II) and copper(II) complexes of tris(β,β,γ-oximinoalkyl)amines are prepared and structurally characterized.