Selective synthesis of 2-aminobenzoxazoles and 2-mercaptobenzoxazoles by using o-aminophenols as starting material

2-Aminobenzoxazoles and 2-mercaptobenzoxazoles were selectively synthesized by treating o-aminophenols with dithiocarbamates and tetramethylthiuram disulfide (TMTD), respectively. With the promotion of NaH/CuI, the reaction of o-aminophenols with dithiocarbamates gave 2-aminobenzoxazoles with good yield (70–92%) in one pot manner, and 2-mercaptobenzoxazoles were synthesized (yield: 55–80%) in the presence of K₂CO₃ by treating o-aminophenols with tetramethylthiuram disulfide (TMTD). The feature of this method includes good to excellent yield, easy performance and broad substrate scope, which makes the protocol practical and attractive in the preparation of some potential pharmaceutically active compounds.     

Lanthanide-catalyzed cyclocarbonylation and cyclothiocarbonylation: a facile synthesis of benzannulated 1,3-diheteroatom five- and six-membered heterocycles

<正>NMR spectra were recorded in CDCl3 or DMSO-d6 on a Bruker Avance 400 operating at 400 MHz with TMS as internal standard. 1H-benzo[d]imidazol-2(3H)-one(3aa) [1]: 1H NMR(400 MHz, DMSO-d6) δ 10.5(s, 2 H, NH), 6.90(s, 4H)(aromatic CH). 13 C NMR(400 MHz, DMSO-d6) δ 155.7, 130.1, 120.9, 108.9. NH HN O3 aa 1-(2-Aminophenyl)-3-phenylurea(3aa′) [2]: 1H NMR(400 MHz, DMSO-d6) δ 8.75(s, 1H), 7.71(s, 1H)(CONH), 7.44(d, J = 8.0 Hz, 2H), 7.33(d, J = 7.8 Hz, 1H), 7.26(t, J = 7.7 Hz, 2H), 6.94(t, J = 7.4 Hz, 1H), 6.84(t, J = 7.4 Hz, 1H), 6.74(d, J = 7.8 Hz, 1H), 6.57(t, J = 7.4 Hz, 1H)(aromatic CH), 4.78(s, 2H)(NH2). 13 C NMR(400 MHz, DMSO-d6) δ 153.6, 141.4, 140.6, 129.2, 125.2, 124.8, 124.2,121.9, 118.4, 117.3, 116.4.     

Kinetics of oxidative ammonolysis of 4-bromo-o-xylene: III. Conversion of 4-bromo-o-tolunitrile as a substrate

Kinetics of oxidative ammonolysis of 4-bromo-o-tolunitrile on V-Sb-Bi-Zr/γ-Al₂O₃-oxide catalyst in the temperature range 633–673 K were studied. We found that the rate of conversion of 4-bromo-o-tolunitrile to the target 4-bromphthalonitrile and CO₂ was described by the half-order equation with respect to the substrate concentration and was independent of the partial pressures of oxygen and ammonia. The byproducts are 4-bromophthalimide formed through the hydrolysis of 4-bromophthalonitrile, CO₂ produced by oxidation of 4-bromo-o-tolunitrile and decarboxylation of 4-bromophthalimide, and 4-brombenzonitrile produced from 4-bromo-o-tolunitrile and 4-bromophthalimide.     

Darstellung von tris(o-deuterophenyl)bismut und bis(o-deuterophenyl)bismutbromid. Zuordnung des paramagnetisch verschobenen 1H-NMR-signals

(o-C₆H₄D)₃Bi was prepared from BiCl₃ and the Grignard reagent obtained from o-C₆H₄ClD (gained by solvolysis of the Grignard reagent from o-C₆H₄BrCl by CH₃COOD). Redistribution of (o-C₆H₄D)₃Bi and BiBr₃ afforded (o-C₆H₄D)₂-BiBr. It is demonstrated, that the paramagnetically shifted ¹H NMR signal observed in phenyl derivatives of bismuth has to be assigned to ortho-protons.     

Synthesis of tricyclic compounds with sulfur and silicon heteroatoms in the central ring

The synthesis of tricyclic derivatives which contain both silicon and sulfur in a central six-, seven- and eight-membered ring are described. Phenothiasilin-5,5-dioxides are prepared by treatment of (o-LiC₆H₄)₂SO₂ with dichlorosilanes. Reduction of the sulfone group is described as well as attempts to introduce aminopropyl substituents at silicon. Thiasilepins are prepared from the Grignard reagent of (o-BrC₆H₄CH₂SC₆H₄Br-o) and reactions of this ring system are described. Reaction of Me₂Si(C₆H₄CH₂Br-o) with Na₂S gave a thiasilocin derivative.     

Catalytic oxidation of volatile organic compounds (VOCs). Oxidation of o-xylene over Pd and Pt/HFAU catalysts

The transformation of o-xylene in low concentration (1 700 ppmv) into air was investigated over Pd and Pt/HFAU catalysts (framework Si/Al ratio equal to 17 and 100). Whatever the catalyst, o-xylene oxidation into CO₂ and H₂O is accompanied by the retention within the zeolite pores of heavy compounds (‘coke’). The relative significance of these reactions depends on the operating conditions (temperature, time-on-stream) and on the catalyst characteristics (Pd or Pt, Si/Al ratio). Over Pt and Pd/HFAU(17), time-on-stream has a positive effect on the xylene oxidation apparently related to the reducibility of Pd and Pt species during the reaction. The higher activity of Pt/HFAU catalysts can be attributed to its greater number of active species (especially Pt⁰). Those active species can be more rapidly formed than Pd⁰ by auto reduction during the calcination of Pt precursor. Whatever the metal, the higher the Si/Al ratio of the support, the faster the xylene oxidation and the lower the coke formation. This can be related to the higher proportion of reduced species (Pd⁰ and Pt⁰) formed on the more dealuminated catalyst but also to the hydrophobicity of the support. Indeed, the hydrophobicity of the zeolite play a positive role in the oxidation activity in presence of steam; the higher the Si/Al ratio of the zeolite, the faster the o-xylene oxidation. Thus a catalyst with a low platinum content supported on a hydrophobic zeolite (0.10 Pt/HFAU(100)) allows to oxidising totally o-xylene at 210 °C in presence of steam.     

Unexpected products from the Fp2-catalyzed reductive cyclization of nitroaromatics bearing pendant unsaturation

A representative o-nitroenone (Z=O) was cyclized by reduction with CO and [CpFe(CO)₂]₂ (Fp₂) as the catalyst to give the corresponding 4-quinolone. In contrast, Baylis-Hillman adducts derived from o-nitrobenzaldehydes were cyclized to N-formylindolines and indoles under the same conditions.     

Pd/C mediated synthesis of 2-substituted benzo[b]furans/nitrobenzo[b]furans in water

An efficient synthesis of 2-alkyl/aryl substituted benzo[b]furans/nitrobenzo[b]furans in water has been accomplished via Pd/C catalyzed reaction of o-iodophenols with terminal alkynes in the presence of PPh₃, CuI and prolinol. This method can tolerate a variety of functional groups present in the alkynes as well as base labile nitro group in the o-iodophenols. The protocol does not require the use of a phase transfer catalyst or water-soluble phosphine ligands and is free from the use of any organic co-solvent.     

Base and catalyst-free synthesis of nitrobenzodiazepines via a cascade N-nitroallylation-intramolecular aza-Michael addition involving o-phenylenediamines and nitroallylic acetates

A [4+3] annulation of o-phenylenediamines with primary nitroallylic acetates affords nitrobenzodiazepines (NBDZs) in good to excellent yield. The reaction which proceeds in MeOH at room temperature in the absence of any base or catalyst involves a cascade S_N2 N-nitroallylation-intramolecular aza-Michael addition sequence. In the case of mono-N-arylated o-phenylenediamines and o-aminobenzamides, the reaction stops at the S_N2 stage affording nitroallylic amines. On the other hand, reaction of o-aminobenzamides with secondary nitroallylic acetates delivers S_N2′ products. Formation of stable S_N2 and S_N2′ products provides insights into the reactivity of primary and secondary nitroallylic acetates and also the mechanism of formation of nitrobenzodiazepines.     

Studies of reactions of o-xylylene-α,α′-dihalides with palladium complexes and the catalytic synthesis of 3-isochromanone

Homogeneous catalysis by palladium complexes with phosphorus(III) ligands of the carbonylation of o-xylylene dihalides in the presence of water to form 3-isochromanone has been studied. Triphenylphosphine was found to provide the most effective catalyst, and by-products and intermediates of systems containing this ligand have been investigated. 2-Indanone is one by-product but is unstable to decomposition under catalytic conditions. Excess PPh₃ is necessary to prolong activity of the catalyst but is also transformed to bis-phosphonium compound [o-C₆H₄(CH₂PPh₃)₂]X₂ (X = Cl or Br); this quaternization has been investigated and the structure of the bromide salt determined by X-ray diffraction. An unstable oxidative addition product of Pd(PPh₃)₄ was detected as a probable intermediate and related to the previously reported but catalytically-inactive complex trans-Pd(o-CH₂C₆H₄CH₂Cl)Cl(PMe₃)₂, which has been structurally characterized by X-ray diffraction in this work.     

Detection and colorimetric determination of the cr04-2 ion with o-dianisidine

A new method is described for the colonmetric determination of CrO₄^-2 ; the reagent used is an acetic solution of o-dianisidino, which gives a red coloration upon acidification. The procedure is described, the limit of perceptibility being of 06 γ/ml Down to this concentration, the coloration still obeys Beer's law and permits the determination with a 15% accuracy. Qualitative investigation of the chromate ion with the above mentioned reagent is also reported. Sensitivity is D = 10^-6.3.     

Organophosphorus-catalyzed relay oxidation of H-Bpin: electrophilic C–H borylation of heteroarenes

A nontrigonal phosphorus triamide (1, P{N[o-NMe-C₆H₄]₂}) is shown to catalyze C–H borylation of electron-rich heteroarenes with pinacolborane (HBpin) in the presence of a mild chloroalkane reagent. C–H borylation proceeds for a range of electron-rich heterocycles including pyrroles, indoles, and thiophenes of varied substitution. Mechanistic studies implicate an initial P–N cooperative activation of HBpin by 1 to give P-hydrido diazaphospholene 2, which is diverted by Atherton–Todd oxidation with chloroalkane to generate P-chloro diazaphospholene 3. DFT calculations suggest subsequent oxidation of pinacolborane by 3 generates chloropinacolborane (ClBpin) as a transient electrophilic borylating species, consistent with observed substituent effects and regiochemical outcomes. These results illustrate the targeted diversion of established reaction pathways in organophosphorus catalysis to enable a new mode of main group-catalyzed C–H borylation.

A nontrigonal phosphorus triamide (1, P{N[o-NMe-C₆H₄]₂}) is shown to catalyze C–H borylation of electron-rich heteroarenes with pinacolborane (HBpin) in the presence of a mild chloroalkane reagent.     

The use of microemulsions in flow injection analysis: Spectrofluorimetric determination of primary amines

The use of microemulsion in flow-injection systems is considered, with particular reference to the determination of C₆C₁₀ primary amines by derivatization with o-phthal-aldehyde and 2-mercaptoethanol. Microemulsions provide an ideal interface for reactions between a water-soluble reagent and a non-aqueous sample. The effect of reaction conditions (R value, droplet concentration, pH and flow rate) on the fluorescence signal is discussed and calibration data for three primary alkylamines are given.     

Ru-catalyzed enantioselective preparation of methyl (R)-o-chloromandelate and its application in the synthesis of (S)-Clopidogrel

The preparation of methyl (R)-o-chloromandelate via Ru-catalyzed asymmetric hydrogenation and transfer hydrogenation was investigated. With Ru-(R,R)-2,4,6-triisopropyl C₆H₂SO₂-DPEN as the catalyst and HCOOH-Et₃N azeotrope as the hydrogen donor, up to 92% ee was obtained in an optional condition. The synthesis of (S)-Clopidogrel was also studied.     

A generalized form of the extraction constant for the partition of a metal chelate between immiscible aqueous and organic phases

The theory underlying the partition of sparingly soluble reagents and their formally neutral metal chelates between an aqueous phase and any immisicible organic phase leads to a generalized extraction constant K^*_ex=K_exSⁿ_r,0/S_c,o where K_ex is the conventional extraction constant and S_r,oS_c,o are the molar solubilities of reagent and metal complex, respectively, in the same organic solvent. The predicted constancy of K^*_ex is confirmed for measurements in seven solvents and for systems involving mono-, di- and tridithizonates of Ag⁺, Zn²⁺ and Bi³⁺, respectively.     

Kinetics of oxidative ammonolysis of 4-bromo-o-xylene: V. Synthesis of 4-bromophthalonitrile

Oxidative ammonolysis of 4-bromo-o-xylene on a V-Sb-Bi-Zr/γ-Al₂O₃ catalyst gives 74.82 mol % of 4-bromophthalonitrile at a high conversion of the starting xylene in a one-cycle process. The process with recirculation results in decreased number of by-products and contribution of deep oxidation and increased selectivity in 4-bromophthalonitrile up to 95.42–96.58%.     

The effect of benzyl amine on the efficiency of the base-catalyzed transamination of α-keto esters

This paper describes the effect of benzyl amine on the base-catalyzed transamination of α-keto esters. Among various benzyl amines examined, o-HOC₆H₄CH₂NH₂ was found to be highly effective for the reaction, affording a wide variety of α-amino esters in good yields. The o-OH group of the benzyl amine facilitates the transamination process likely via H-bond. Moderate enantiomeric excess was obtained for α-amino ester when a quinine derived catalyst was used.     

Iridium-catalyzed intramolecular CN and CO/S cross-coupling reactions: Preparation of benzoazole derivatives

The irdium-catalyzed intramolecular arylcarbon-hetero cross-coupling reactions with o-haloarylamides or o-haloarylamidine have been effectively achieved using KOAc and just 1 mol% catalyst. The [Ir(cod)Cl]₂ was proved to be more potential for smoothly assembling functional structures benzimidazoles, benzoxazoles and benzothiazoles, which was superior to Cu- and Pd-catalyzed systems. Simultaneously, a concise and efficient synthesis of tafamidis was developed in 5-g scale.     

Hydrogenolysis of hydrocarbons over supported catalysts derived from metal carbonyl clusters

A comparison between the activities of silica-supported ruthenium, rhodium and platinum catalysts prepared from metal cluster compounds and their conventional analogues towards the activation of saturated hydrocarbons has been made. Ruthenium cluster-derived catalysts display greatly enhanced activity for the complete hydrogenolysis of straight chain aliphatic hydrocarbons to methane and provide a temperature advantage of 150°C relative to conventionally prepared ruthenium catalysts where only moderate hydrocarbon conversions are noted. The increased activity superficially correlates with the smaller metal crystallite sizes (15–20 Å) reproducibly obtainable using metal cluster compounds as catalyst precursors. The highly specific activity for the hydrogenolysis of C-C bonds in saturated hydrocarbons has been applied to the selective cleavage of the alkyl group in ethylbenzene, giving toluene and methane. Conversions of up to 30% ethylbenzene have been observed at 225°C and 1 atm using a Ru₃(CO)₁₂/SiO₂-based catalyst. The xylenes, particularly o-xylene, are much less susceptible to hydrogenolysis and, at 225°C, relative hydrocarbon destruction rates of 30 : 1 and 7 : 1 have been observed using mixed feeds of ethylbenzene/o-xylene and ethylbenzene/p-xylene, respectively. Such a catalyst system can, in principle, therefore provide a means of separating ethylbenzene from its mixtures with xylenes.     

A convenient method for the preparation of oxazaborolidine catalyst in situ using (S)-α,α-diphenylpyrrolidinemethanol,tetrabutylammonium borohydride,and methyl iodide for the asymmetric reduction of prochiral ketones

An oxazaborolidine catalyst is readily prepared in situ at 25 °C in THF using (S)-α,α-diphenylpyrrolidinemethanol and borane generated from tetrabutylammonium borohydride/CH₃I reagent system. The oxazaborolidine/BH₃ reagent system prepared in this way is useful for the reduction of prochiral ketones to the corresponding alcohols with up to 99% ee.