Zhao-Yang Wang

Rapid and Cheap Synthesis of Benzimidazoles via Intermittent Microwave Promotion: A Simple and Potential Industrial Application of Air as Oxidant

Using inexpensive KI as the catalyst in the presence of ambient air, benzimidazoles were synthesized from aromatic aldehydes and o-phenylenediamine with excellent yields via intermittent microwave irradiation without reflux equipment. The synthesis process was mild and only needed only a short reaction time (7–10 min). As a simple example of the utilization of molecular oxygen under mild conditions, this method provides a novel way to synthesize benzimidazoles. The industrial synthesis of benzimidazoles may be realized by a cycle of microwave irradiation.

Reaction of 5-alkoxy-3,4-dihalo-2(5H)-furanones with secondary amines: expected versus unanticipated products and their preliminary bioactivity investigations

Using KF as base and THF as solvent, 5-alkoxy-3,4-dihalo-2(5H)-furanones were reacted with secondary amines. The normal products, β-amino-2(5H)-furanones, were obtained via the tandem Michael addition-elimination reaction as expected in most cases. However, the reaction between diisopropylamine and 3,4-dihalo-5-methoxy-2(5H)-furanones yielded unanticipated products, methyl (E)-2-halo-4-(diisopropylamino)-4-oxobut-2-enoates. The possible synthetic mechanism involving a rearrangement reaction was proposed. The biological activity assay of products derived from the reactions of 5-alkoxy-3,4-dihalo-2(5H)-furanones with different amino compounds was preliminarily investigated by the MTT method on A549 cells in vitro, which revealed that some derivatives of amino acid esters with a benzene ring exhibited the best anticancer bioactivity.Graphical Abstract

Synthesis of biodegradable material poly(lactic acid-co-sorbitol) via direct melt polycondensation and its reaction mechanism

To further verify the mechanism of forming multi-core structure during the direct melt copolycondensation of lactic acid (LA) with compounds containing multi-hydroxyl groups, the biodegradable material poly(lactic acid-co-sorbitol) [P(LA-co-SB)] was synthesized by using D,L-lactic acid (D,L-LA) and sorbitol (SB) as starting materials. For the molar feed ratio n(LA)/n(SB) of 120/1, optimal synthetic conditions were investigated. After prepolymerization at 140xa0°C for 8xa0h, melt copolymerization with the catalysis of SnO (0.5 wt %) at 160xa0°C for 6xa0h gave a polymer with the biggest intrinsic viscosity ([η]) 0.91xa0dL•g−1. The copolymer P(LA-co-SB)s obtained at different molar feed ratios were characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H-NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results show that the weight-average molecular weight (Mw) doesn’t increase all the time along with the increasing of the molar feed ratio n(LA)/n(SB), but a Mw peak value exists, which validates again the special Mw peak phenomenon during the direct melt copolycondensation of LA with the monomers containing multifunctional groups (including polyols, e.g. glycerol). However, compared with the results of using glycerol as the core, the mechanism of forming the multi-core copolymer is somewhat different due to SB’s different structure. All the results show that the Mw peak value of the copolymers with multi-core structure is related to not only the number of hydroxyl groups in polyols, but also the reactivity of hydroxyl groups resulted from their type, and the steric hindrance of hydroxyl groups in the polyol.

Synthesis of N-(5-alkoxy-2(5H)-furanonyl) amino acid propargyl esters

Using K2CO3 as a base and CH3CN as solvent, different kinds of N-[5-alkoxy-2(5H)-furanonyl] amino acids were reacted with propargyl bromide via substitution reaction at 40xa0°C to give 16 N-[5-alkoxy-2(5H)-furanonyl] amino acid propargyl esters with the yields of 44–85% (mostly over 74%). The structures of all newly synthesized compounds were elucidated and confirmed by FTIR, UV, 1H NMR, 13C NMR, MS, and elemental analysis. The rapid, efficient, and brief synthesis of the series propargyl esters with multiple bioactive units, will afford not only a basis for the activity test of potential drug molecules, but also an important synthetic strategy for 2(5H)-furanone derivatives with polyfunctional groups.

Synthesis and Characterization of a Novel Biodegradable Material, Poly(Lactic Acid-co-Tryptophane)

With cheap D,L-lactic acid (D,L-LA) and tryptophan (Try) as starting materials, a novel biodegradable material, poly(lactic acid-co-tryptophane) (P(LA-co-Try)), was synthesized via melt co-polycondensation. When the molar feed ratio LA/Try is 90:10, the influences of different conditions, including catalyst kinds and its dosage, co-polymerization time and temperature on the synthesis of the polymer are discussed. When SnCl2/ZnO (weight ratio 7:3) was used as catalyst at a dose of 0.7 wt% of the pre-polymer, 8 h direct-melt polycondensation at 160°C and absolute pressure of 70 Pa after pre-polymerization gave the co-polymer with a maximum intrinsic viscosity [η] of 0.73 dl/g. The structure of the co-polymer was characterized by FT-IR and 1H-NMR. According to the optimal synthetic conditions, co-polymers with different molar feed ratios were synthesized and systematically characterized by [η], FT-IR, 1H-NMR, GPC, DSC and XRD. The GPC results show that the maximum weight-average molecular weight (M w) of P(LA-co-Try) is 6500 when the molar feed ratio LA/Try is 98:2. With the increase of the molar feed ratio of Try, [η], M w and its polydispersity index (M w /M n) decrease gradually. Due to the introduction of Try with a big aromatic ring into the co-polymer, the glass-transition temperature (T g) increases gradually with the increasing feed charge of Try and all co-polymers are amorphous. Direct-melt co-polycondensation is a cheap and practical method for the synthesis of Try-modified poly(lactic acid), a potential biomedical material, especially when used as a drug-delivery carrier.

Synthesis and characterization of a novel functional biodegradable material, poly(lactic acid-co-borneol)

Directly starting from D,L-lactic acid (LA) and L-borneol, novel biodegradable material poly(lactic acid-co-borneol) (PLAB) was synthesized via melt polycondensation. When the molar feed ratio LA/borneol is 64/1, the influences of different conditions including catalyst kinds and its dosage, copolymerization time, and temperature on the synthesis of the polymer are discussed. When the SnO was used as catalyst and the dosage was 0.3 wt% of the prepolymer, the 5u2009h direct melt polycondensation at 170u2009°C and absolute pressure of 70u2009Pa after prepolymerization gave the copolymer with the maximum intrinsic viscosity [η], 1.51u2009dLu2009g−1. The structure of copolymer was confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR). According to the appropriate synthetic conditions, the copolymers with different molar feed ratios were synthesized and systematically characterized by [η], gel permeation chromatography (GPC), differential scanning calorimetry, thermogravimetric, and X-ray diffraction (XRD). The GPC results show that the maximum weight average molecular weight (M w) of PLAB is 11,900, when the molar feed ratio LA/borneol is 64/1. With the increase of the molar feed ratio of borneol, [η], M w and its polydispersity index (M w/M n) increase gradually. Due to the introduction of borneol into the copolymer, the glass-transition temperature (T g) decreases gradually with the increasing feed ratio of borneol. The direct melt copolycondensation is a cheap and practical method for the synthesis of borneol modified polylactic acid, a potential solid borneol flavor, polymeric drug, and functional drug carrier.

Influence of electric field coupling model on the simulated performances of a GaN based planar nanodevice

The performances of a two-dimensional electron gas (2DEG) based planar nanodevice are studied by a two-dimensional-three-dimensional (2D-3D) combined model and an entirely 2D model. In both models, 2DEGs are depicted by 2D ensemble Monte Carlo (EMC) method. However electric field distributions in the devices are obtained by self-consistently solving 2D and 3D Poisson equations for the 2D model and the 2D-3D model, respectively. Simulation results obtained by both models are almost the same at low bias while showing distinguished differences at high bias. The 2D model predicts larger output current and slightly higher threshold voltage of Gunn oscillations. Although the fundamental frequencies of current oscillations obtained by both models are similar, the deviation of wave shape from sinusoidal waveform obtained by the 2D model is more serious than that obtained by 2D-3D model. Moreover, results obtained by the 2D model are more sensitive both to the bias conditions and to the change of device parameters. Interestingly, a look-like second harmonic oscillation has been observed at DC bias. We contribute the origin of divergences in simulation results to the different coupling path of electric field in the two models. And the second-harmonic oscillations at DC bias should be the result of the appearance of concomitant oscillations beside the channel excited by strong electric-field effects.

N-{4-Bromo-2-[(S)-menth­yloxy]-5-oxo-2,5-dihydro-3-fur­yl}-l-valine

The title compound, C19H30BrNO5, was obtained via a tandem asymmetric Michael addition–elimination reaction of 3,4-dibromo-5-[(S)-l-menthyloxy]furan-2(5H)-one and l-valine in the presence of potassium hydroxide. The molecular structure contains an approximately planar (r.m.s. deviation = 0.0204u2005Å) five-membered furanone ring and a six-membered menthyloxy ring adopting a chair conformation. The crystal packing is stabilized by intermolecular O—H⋯O and N—H⋯O hydrogen bonding.

N-[(2S)-4-Chloro-2-(l-menthyloxy)-5-oxo-2,5-dihydro-3-furyl]-l-alanine.

The title compound, C17H26ClNO5, was prepared via a tandem asymmetric Michael addition–elimination reaction of (5S)-3,4-dichloro-5-(l-menthyloxy)furan-2(5H)-one and l-alanine in the presence of potassium hydroxide. The five-membered furanone ring is approximately planar while the six-membered menthyloxy ring adopts a chair conformation. The crystal packing is stabilized by intermolecular O—H⋯O and N—H⋯O hydrogen bonds.

3,3'-Dibromo-5,5'-bis-[(S)-l-menth-yloxy]-4,4'-(hexane-1,6-diyldiimino)difuran-2(5H)-one.

The title compound, C34H54Br2N2O6, was obtained by the Michael addition–elimination reaction of (5S)-5-(l-menthyloxy)-3,4-dibromofuran-2(5H)-one with 1,6-hexanediamine in the presence of triethylamine. The crystal structure contains two chiral five-membered furanone rings, in twist and envelope conformations, and two six-membered cyclohexane rings in chair conformations.