Regioselective Alkylative Carboxylation of Allenamides with Carbon Dioxide and Dialkylzinc Reagents Catalyzed by an N‐Heterocyclic Carbene–Copper Complex

The alkylative carboxylation of allenamide catalyzed by an N‐heterocyclic carbene (NHC)–copper(I) complex [(IPr)CuCl] with CO₂ and dialkylzinc reagents was investigated. The reaction of allenamides with dialkylzinc reagents (1.5 equiv) and CO₂ (1 atm.) proceeded smoothly in the presence of a catalytic quantity of [(IPr)CuCl] to afford (Z)‐α,β‐dehydro‐β‐amino acid esters in good yields. The reaction is regioselective, with the alkyl group introduced onto the less hindered γ‐carbon, and the carboxyl group introduced onto the β‐carbon atom of the allenamides. The first step of the reaction was alkylative zincation of the allenamides to give an alkenylzinc intermediate followed by nucleophilic addition to CO₂. A variety of cyclic and acyclic allenamides were found to be applicable to this transformation. Dialkylzinc reagents bearing β‐hydrogen atoms, such as Et₂Zn or Bu₂Zn, also gave the corresponding alkylative carboxylation products without β‐hydride elimination. The present methodology provides an easy route to alkyl‐substituted α,β‐dehydro‐β‐amino acid ester derivatives under mild reaction conditions with high regio‐ and stereoselectivtiy.     

Synthesis,characterization, and antimicrobial activity of new benzofuran derivatives

Russian Journal of General Chemistry - A novel series of (5-substituted-1-benzofuran-2-yl)(2,4-substituted phenyl)methanones (4a–4i) have been prepared by the Knoevenagel condensation of...     

Investigations on discotic liquid crystals

ABSTRACT

Discotic liquid crystals (DLCs) have reached from curiosity to commodity in a short span of time. Tremendous development has been observed in the field of DLCs in the past few years due to their vide-viewing display and unidirectional conducting properties. In this article, I present some aspects of research carried out by me and my collaborators on DLCs. This work was presented at the Asian Conference on Liquid Crystals (ACLC 2019) at Shenzhen, China during January 17–18, 2019.     

Bi2O3/FAp,a sustainable catalyst for synthesis of dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives through green strategy

The bismuth loaded on fluorapatite (Bi₂O₃/FAp) proved to be an excellent catalyst for the synthesis of novel dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives via a three-component reaction involving the mixture of 1H-1,2,4-triazol-5-amine, ethyl cyanoacetate or ethyl acetoacetate, and different benzaldehydes in ethanol at room temperature. The catalyst material was characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy techniques. The efficacy of Bi₂O₃/FAp as a heterogeneous catalyst was evaluated with the loading of different wt% of bismuth on FAp. The 2.5% bismuth on FAp performed extremely well as a catalyst with a high yield of products (92%–96%) in a short reaction time (25–35 min). The catalyst was recovered by simple filtration. It showed undiminished activity up to five runs. Simple work-up, room temperature reaction, short reaction time, high yields, no column chromatography, and good reusability of catalyst are the merits of the proposed protocol. In addition, this process offers 100% carbon efficiency and 98% atom economy with noteworthy fiscal and environmental benefits.     

Epoxidation of trans-stilbene with molecular oxygen over an eco-friendly heterogeneous cobalt oxide/reduced graphene oxide composite material

Research on Chemical Intermediates - We report the synthesis of 1, 5, 10 wt% cobalt oxide/reduced graphene oxide (CoO–RGO) composite materials by a simple solvothermal method. We assessed...     

Synthesis of RE Y zeolite for formulation of FCC catalyst and the catalytic performance in cracking of n-hexadecane

Research on Chemical Intermediates - This study presents the synthesis of rare earth-doped Y (RE Y) zeolite, its application in formulation of a fluid catalytic cracking (FCC) catalyst and the...     

Naproxen Inhibits UVB‐induced Basal Cell and Squamous Cell Carcinoma Development in Ptch1+/−/SKH‐1 Hairless Mice

Naproxen possesses anti‐proliferative and pro‐apoptotic effects besides its known anti‐inflammatory functions. Here, we demonstrate the anticancer effects of naproxen against UVB‐induced basal cell carcinoma (BCCs) and squamous cell carcinoma (SCCs) in a highly susceptible murine model of UVB carcinogenesis. Naproxen significantly inhibited UVB‐induced BCCs and SCCs in this model. Tumor number and volume were significantly decreased (P < 0.005 and P < 0.05, respectively). Inhibition in UVB‐induced SCCs and BCCs was 77% and 86%, respectively, which was associated with reduced PCNA and cyclin D1 and increased apoptosis. As expected, inflammation‐related iNOS, COX‐2 and nuclear NFκBp65 were also diminished by naproxen treatment. Residual tumors excised from naproxen‐treated animal were less invasive and showed reduced expression of epithelial‐mesenchymal transition (EMT) markers N‐cadherin, Vimentin, Snail and Twist with increased expression of E‐cadherin. In BCC and SCC cells, naproxen‐induced apoptosis and activated unfolded protein response (UPR) signaling with increased expression of ATF4, p‐eIF2α and CHOP. Employing iRNA‐based approaches, we found that naproxen‐induced apoptosis was regulated by CHOP as sensitivity of these cutaneous neoplastic cells for apoptosis was significantly diminished by ablating CHOP. In summary, these data show that naproxen is a potent inhibitor of UVB‐induced skin carcinogenesis. ER stress pathway protein CHOP may play an important role in inducing apoptosis in cancer cells.     

“On water” ultrasound-assisted one pot efficient synthesis of functionalized 2-oxo-benzo[1,4]oxazines: First application to the synthesis of anticancer indole alkaloid,Cephalandole A

For the first time, an efficient, simple, synthetic green protocol for the one-pot synthesis of functionalized 2-oxo-benzo[1,4]oxazines 24–29 in water under ultrasound irradiation is presented. As compared to conventional methods, the present protocol avoids traditional chromatography and purification steps and furnished the target molecules in excellent yields (upto 98%) with no side products. The methodology was also demonstrated on gram scale synthesis. Moreover, functionalized 2-oxo-quinoxaline analogues 31–33, another class of bio-active heterocyclic scaffolds, were also prepared using this method. For the first time, this protocol was successfully applied in the synthesis of the anticancer indole alkaloid, Cephalandole A 35.     

Morphological change of crystalline polymer films by annealing: substrate‐ and heating/cooling‐rate‐dependent surface roughness

We study the morphological change of crystalline polymer films by annealing using atomic force microscope, X‐ray diffraction, and Fourier transform infrared spectroscopy techniques. As typical samples, we employ high‐density and low‐density polyethylene films prepared by the cast method. After annealing at 135 °C for 4 h, the surface roughness of polyethylene films by the atomic force microscope significantly increases, and the crystallite size by the X‐ray diffraction also shows some increase, while the Fourier transform infrared spectroscopy spectrum hardly exhibits any change. This can be well explained as a result of the growth of crystal structure by recrystallization during annealing. More interestingly, we find that the choice of the substrate and also the heating/cooling rates for annealing significantly influences the surface roughness of the films. Copyright © 2017 John Wiley & Sons, Ltd.