Direct conversion of chitin derived N-acetyl-D-glucosamine into 3-acetamido-5-acetylfuran in deep eutectic solvents.

3-Acetylamino-5-acetylfuran (3A5AF) is an important nitrogen-containing fine chemical with broad application prospects and high research value. Herein, we report a novel method for the conversion of N-acetyl-d-glucosamine (NAG) to 3A5AF in the choline chloride-based deep eutectic solvents (DESs). The catalytic activities of various DESs have been smoothly screened, and DES 2 (choline chloride/PEG-200/boronic acid = 1/1/0.5) displayed the best catalytic performance. In the absence of any additional solvent, catalyst and additive, product 3A5AF was obtained in 18.3% yield after reacting at 180 °C for 15 min under atmospheric condition. In addition, DES 2 showed a good reusability. The possible reaction pathway was elucidated on the basis of the results of LC-MS and 13C NMR spectra. This study provided a new perspective for the application of DES in the conversion of chitin biomass.

Cleavage of non-polar C(sp2)‒C(sp2) bonds in cycloparaphenylenes via electric field-catalyzed electrophilic aromatic substitution.

Electrophilic aromatic substitution (EAS) is one of the most fundamental reactions in organic chemistry. Using an oriented external electric field (OEEF) instead of traditional reagents to tune the EAS reactivity can offer an environmentally friendly method to synthesize aromatic compounds and hold the promise of broadening its scope. Despite these advantages, OEEF catalysis of EAS is difficult to realize, due to the challenge of microscopically orienting OEEF along the direction of electron reorganizations. In this work, we demonstrate OEEF-catalyzed EAS reactions in a series of cycloparaphenylenes (CPPs) using the scanning tunneling microscope break junction (STM-BJ) technique. Crucially, the unique radial π-conjugation of CPPs enables a desired alignment for the OEEF to catalyze the EAS with Au STM tip (or substrate) acting as an electrophile. Under mild conditions, the OEEF-catalyzed EAS reactions can cleave the inherently inert C(sp2)-C(sp2) bond, leading to high-yield (~97%) formation of linear oligophenylenes terminated with covalent Au-C bonds. These results not only demonstrate the feasibility of OEEF catalysis of EAS, but also offer a way of exploring new mechanistic principles of classic organic reactions aided by OEEF.

Valorization of chitin biomass into N-containing chemical 3-acetamido-5-acetylfuran catalyzed by simple Lewis acid.

3-Acetamido-5-acetylfuran(3A5AF) is a nitrogen-containing fine chemical and has broad application prospects and high research value. Herein, we report a mild and efficient method for the synthesis of 3A5AF from N-acetyl-d-glucosamine (NAG). The influence of solvent, temperature and additive on the catalytic performance was also studied. The Lewis acids with high catalytic efficiency have been smoothly screened. The highest yield (41.57%) of 3A5AF was obtained in the presence of B2O3 and MgCl2·6H2O at 180 °C for 60 min under normal atmospheric conditions. The reaction pathway was explored by LC-MS, 1H NMR, 13C NMR and FT-IR spectra. Compared with the microwave method and hydrothermal method, the optimized reaction condition was relatively mild. Moreover, the catalyst MgCl2·6H2O is low-cost and environmentally friendly.

Single cycloparaphenylene molecule devices: Achieving large conductance modulation via tuning radial π-conjugation.

Conjugated macrocycles cycloparaphenylenes (CPPs) have unusual size-dependent electronic properties because of their unique radially π-conjugated structures. Contrary to linearly π-conjugated molecules, their highest occupied molecular orbital (HOMO)­lowest unoccupied molecular orbital (LUMO) gap shrinks as the molecular size reduces, and this feature can, in principle, be leveraged to achieve unexpected size-dependent transport properties. Here, we examine charge transport characteristics of [n]CPPs (n = 5 to 12) at the single molecule level using the scanning tunneling microscope­break junction technique. We find that the [n]CPPs have a much higher conductance than their linear oligoparaphenylene counterparts at small ring size and at the same time show a large tunneling attenuation coefficient comparable to saturated alkane series. These results show that the radially π-conjugated molecular systems can offer much larger conductance modulation range than standard linear molecules and can be a new platform for building molecular devices with highly tunable transport behaviors.

Efficient conversion of N-acetyl-D-glucosamine into nitrogen-containing compound 3-acetamido-5-acetylfuran using amino acid ionic liquid as the recyclable catalyst.

Chitin is the most widely distributed oceanic biomass resources. Its monomer unit, N-acetyl-D-glucosamine (NAG), contains precious atomic nitrogen and represents a potential feedstock for the manufacture of regenerative organic nitrogen chemicals. Herein, the conversion of NAG to the platform chemical, 3-acetamido-5-acetylfuran (3A5AF), catalyzed by amino acid ionic liquids, was investigated. The reaction, catalyzed by a very small amount of glycine chloride ionic liquid without any additives, could yield 43.22% 3A5AF in 10 min. By adding CaCl2, a higher yield up to 52.61% was obtained. This work demonstrated the conversion of chitin biomass to 3A5AF in higher yield without using a boron-based catalyst for the first time. Moreover, the ionic liquid catalyst exhibited excellent recyclability, and afforded 43.22-36.59% yield over during eight cycles. This research provides new and green procedures to convert shellfish fishery waste into value-added platform chemicals.

Hydrothermal conversion of N-acetyl-d-glucosamine to 5-hydroxymethylfurfural using ionic liquid as a recycled catalyst in a water-dimethyl sulfoxide mixture.

Here, N-acetyl-d-glucosamine (GlcNAc), the monomer composing the second most abundant biopolymer, chitin, was efficiently converted into 5-hydroxymethylfurfural (5-HMF) using ionic liquid (IL) catalysts in a water/dimethyl sulfoxide (DMSO) mixture solvent. Various reaction parameters, including reaction temperature and time, DMSO/water mass ratios and catalyst dosage were optimized. A series of ILs with different structures were analyzed to explore their impact on GlcNAc conversion. The substrate scope was expanded from GlcNAc to d-glucosamine, chitin, chitosan and monosaccharides, although 5-HMF yields obtained from polymers and other monosaccharides were generally lower than those from GlcNAc. Moreover, the IL N-methylimidazolium hydrogen sulfate ([Hmim][HSO4]) exhibited the best catalyst performance (64.6% yield) when GlcNAc was dehydrated in a DMSO/water mixture at 180 °C for 6 h without the addition of extra catalysts. To summarize, these results could provide knowledge essential to the production of valuable chemicals that are derived from renewable marine resources and benefit biofuel-related applications.

Organocatalytic upgrading of furfural and 5-hydroxymethyl furfural to C10 and C12 furoins with quantitative yield and atom-efficiency.

There is increasing interest in the upgrading of C5 furfural (FF) and C6 5-hydroxymethyl furfural (HMF) into C10 and C12 furoins as higher energy-density intermediates for renewable chemicals, materials, and biofuels. This work utilizes the organocatalytic approach, using the in situ generated N,S-heterocyclic carbene catalyst derived from thiazolium ionic liquids (ILs), to achieve highly efficient self-coupling reactions of FF and HMF. Specifically, variations of the thiazolium IL structure have led to the most active and efficient catalyst system of the current series, which is derived from a new thiazolium IL carrying the electron-donating acetate group at the 5-ring position. For FF coupling by this IL (0.1 mol %, 60 °C, 1 h), when combined with Et3N, furoin was obtained in >99% yield. A 97% yield of the C12 furoin was also achieved from the HMF coupling by this catalyst system (10 mol % loading, 120 °C, 3 h). On the other hand, the thiazolium IL bearing the electron-withdrawing group at the 5-ring position is the least active and efficient catalyst. The mechanistic aspects of the coupling reaction by the thiazolium catalyst system have also been examined and a mechanism has been proposed.

1-Methylimidazolium hydrogen sulfate catalyzed convenient synthesis of 2,5-dimethyl-N-substituted pyrroles under ultrasonic irradiation.

Ionic liquid [HMIM]HSO4 was found to be an efficient catalyst for the synthesis of N-substituted pyrroles through the reaction of 2,5-hexanedione with amines under ultrasonic irradiation at room temperature. These reactions proceed with good yields under short reaction time. Furthermore, the green catalytic system can be recycled specific times with no decreases in yields and reaction rates.

4-Benzyl-4-ethyl-morpholin-1-ium hexa-fluoro-phosphate.

The asymmetric unit of the title compound, C(13)H(20)NO(+)·PF(6) (-), contains two cations, one complete anion and two half hexa-fluoro-phosphate anions having crystallographically imposed twofold rotation symmetry. In the cations, the morpholine rings are in a chair conformation. In the crystal, ions are linked by weak C-H⋯F hydrogen bonds into a three-dimensional network.

Ionic liquid under ultrasonic irradiation towards a facile synthesis of pyrazolone derivatives.

Ionic liquid [HMIM]HSO(4) was found to be an efficient catalyst for the synthesis of 4-[(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-phenyl-methyl]-5-methyl-2-phen-yl-1,2-dihydro-pyrazol-3-ones through the condensation reaction of arylaldehydes and 3-methyl-1-phenyl-5-pyrazolone under ultrasonic irradiation at room temperature. The present methodology offers several advantages such as excellent yields, simple procedure and mild conditions.

Ionic liquid [EMIM]OAc under ultrasonic irradiation towards the first synthesis of trisubstituted imidazoles.

The ionic liquid 1-ethyl-3-methylimidazole acetate ([EMIM]OAc) was found to be a mild and effective catalyst for the efficient, one-pot, three-component synthesis of 2-aryl-4,5-diphenyl imidazoles at room temperature under ultrasonic irradiation. This procedure has many obvious advantages compared to those reported in the previous literatures, including avoiding the use of harmful catalysts, reacting at room temperature, high yields, simplicity of the methodology.

4-Benzyl-4-methyl-morpholinium hexa-fluoro-phosphate.

In the title compound, C(12)H(18)NO(+)·PF(6) (-), the asymmetric unit consists of two cation-anion pairs. The six F atoms of one anion are disordered over two sets of sites in a 0.592 (6):0.408 (6) ratio. The morpholinium rings adopt chair conformations.

3,3,6,6-Tetra-methyl-9-(2-nitro-phen-yl)-3,4,6,7-tetra-hydro-2H-xanthene-1,8(5H,9H)-dione.

In the title compound, C(23)H(25)NO(5), the pyran ring adopts a flattened boat conformation, while the two cyclo-hexenone rings are in envelope conformations. The 3-nitro-phenyl ring is almost perpendicular to the pyran ring, making a dihedral angle of 87.1 (3)°.

An efficient ultrasound-promoted method for the one-pot synthesis of 7,10,11,12-tetrahydrobenzo[c]acridin-8(9H)-one derivatives.

A new, efficient and general method for preparation of 7,10,11,12-tetrahydrobenzo[c]acridin-8(9H)-one derivatives using ultrasound irradiation is reported. Under ultrasound, the reaction time is short, the yields are high and the reaction conditions are mild.

Ultrasound-promoted synthesis of oximes catalyzed by a basic ionic liquid [bmIm]OH.

The basic ionic liquid 1-butyl-3-methylimidazolium hydroxide, [bmIm]OH, efficiently catalyzes the condensation reaction of aldehydes and ketones with hydroxylamine hydrochloride under ultrasound irradiation. Compared with conventional methods, the main advantages of the present procedure are milder conditions, shorter reaction time and higher yields.

9,9-Dimethyl-12-phenyl-8,9-dihydro-12H-benzo[a]xanthen-11(10H)-one.

The title compound, C(25)H(22)O(2), was synthesized via the three-component coupling of benzaldehyde, 2-naphthol and 5,5-dimethyl-cyclo-hexane-1,3-dione. In the crystal structure, centrosymmetrically related mol-ecules are linked into dimers by pairs of inter-molecular C-H⋯O hydrogen bonds. The dimers are further connected into a three-dimensional network by π-π aromatic stacking inter-actions involving the naphthalene ring system, with centroid-centroid separations of 3.695 (7) Å.

Hexaaquanickel(II) bis[2-carboxylato-2-(isothiouronium-S-ylmethyl)propane-1,3-diyl phosphate] hexahydrate.

In the title complex, [Ni(H(2)O)(6)](C(6)H(10)N(2)O(6)PS)(2) x 6 H(2)O, the asymmetric unit consists of one-half of an Ni atom (which lies on an inversion centre) with three coordinated water molecules, one complete 2-carboxylato-2-(isothiouronium-S-ylmethyl)propane-1,3-diyl phosphate anion and three noncoordinated water molecules. The hexaaquanickel(II) cations have distorted octahedral coordination and are connected via water chains to form two-dimensional supramolecular networks parallel to the ab plane. The phosphate ester anion is linked via N-H...O and O-H...O hydrogen bonds, thus creating various ring, dimer and chain hydrogen-bonding patterns, and building up a second two-dimensional supramolecular network parallel to the ab plane. The crystal structure is further stabilized by an intra- and interlayer hydrogen-bond network. This work illustrates that a carboxylate with a caged phosphate ester can open its ring in the presence of dichloridotetrakis(thiourea)nickel, and the resulting polyfunctional anion can be used for constructing a complex hydrogen-bonding scheme.

Poly[[diaquabis(mu2-1-oxo-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-4-carboxylato)copper(II)] dihydrate].

The asymmetric unit of the title complex, {[Cu(C(5)H(6)O(6)P)(2)(H(2)O)(2)] x 2 H(2)O}(n), consists of half a Cu atom, one complete 1-oxo-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-4-carboxylate anion ligand and two non-equivalent water molecules. The Cu atom lies on a crystallographic inversion centre and has an elongated axially distorted octahedral environment. A two-dimensional layer structure parallel to (100) is formed as a result of the connectivity brought about by each anion bonding to two different Cu atoms via a carboxylate O atom and a bridging O atom of a C-O-P group. The water molecules participate in extensive O-H...O hydrogen bonding. Neighbouring layers are linked together by intermolecular hydrogen-bonding interactions. The crystal structure is characterized by intra- and interlayer motifs of a hydrogen-bonded network. This study demonstrates the usefulness of carboxylates with caged phosphate esters in crystal engineering.

4-Allyl-4-ethyl-morpholinium chloride.

In the title molecular salt, C(9)H(18)NO(+)·Cl(-), the morpholine ring adopts a chair conformation. In the crystal structure, intra-molecular C-H⋯Cl bonds occur and inter-molecular C-H⋯O and C-H⋯Cl hydrogen bonds link the mol-ecules.

Bis(acetophenone oxime) O,O'-methyl-ene ether.

In the mol-ecule of the title compound, C(17)H(18)N(2)O(2), the dihedral angle between the aromatic rings is 74.26 (3)°. The oxime units are oriented at dihedral angles of 7.66 (3) and 33.06 (3)° with respect to the adjacent rings, and they have E configurations about the C=N bonds.