3-[4-Bromo-α(<Emphasis Type="Italic">R</Emphasis>*)-methoxybenzyl]-6-chloro-3(<Emphasis Type="Italic">S</Emphasis>*),4(<Emphasis Type="Italic">S</Emphasis>*)-dihydroxychroman: X-ray and DFT Studies

Sodium borohydride reduction of E-3-benzylidenechromanone epoxides in dry methanol has afforded 3(S*), 4(S*)-dihydroxy-3-[α(R*)-methoxybenzyl]chromans as an interesting class of products, the structures of which have been assigned mainly from spectral data and consideration of the mechanistic aspects. X-ray diffraction study of one of them, 3-[4-bromo-α(R*)-methoxybenzyl]-6-chloro-3(S*),4(S*)- dihydroxychroman, is performed. The title compound crystallizes in the monoclinic sp. gr. P2₁/n, with a = 13.336(6) Å, b = 10.866(5) Å, c = 27.166(11) Å, β = 95.193(6)°, V = 3920(3) ų, and Z = 8. Supramolecular construction of the compound involves O–H···O intermolecular hydrogen bonds as well as three other types of non-covalent interactions which are responsible for crystal packing. Density functional theory was applied for geometry optimization, molecular orbital calculations, and prediction of UV spectral features. The geometric parameters (bond lengths, bond angles, and dihedral angles) for the representative compound obtained from density functional theory with B3LY6-31G basis set were in good agreement with experimental values.     

In silico fight against novel coronavirus by finding chromone derivatives as inhibitor of coronavirus main proteases enzyme

Structural Chemistry - Novel coronavirus, 2019-nCoV is a danger to the world and is spreading rapidly. Very little structural information about 2019-nCoV make this situation more difficult for drug...     

Synthesis and Chemical Reactivity of 4‐Oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde

4‐Oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde (chromone‐3‐carboxaldehyde or 3‐formylchromone) 1 is an important biologically active compound. It can serve as a precursor in the synthesis of a wide range of heterocyclic systems having chromone moiety, many of which exhibit broad spectrum of biological activities such as anti‐mutagenisity, cytotoxicity, thymidine phosphorylase inhibitor, and anti‐HIV activity. During the last decade, the title compound was studied extensively. The review presents an overall survey of the synthesis, chemical reactivity, and biological activities of 4‐oxo‐4H‐1‐benzopyran‐3‐carboxaldehydes and some of its derivatives.     

Newly designed Mn (III)–W(V) bimetallic assembly built by manganese (III) Schiff–base and octacyanotungstate(V) building blocks: Structural topologies,and magnetic features

New complex [Mn (SB)₂(DMF)₂] [W (CN)₈] hereafter referred to as complex 1 , which was prepared by self–assembly of [Mn (SB)₂(DMF)₂]³⁺ and [W (CN)₈]³⁻ and structurally characterized by elemental analysis, infrared (IR) and single crystal X–ray techniques (H₂SB is Schiff base derived from the condensation of salicylaldehyde and N,N–diethylethylenediamine and DMF is dimethylformamide). The structure consists of 1–D supramolecular chains and further stacks to give a 3–D supramolecular architecture whose molecular fragments are linked by hydrogen bond as well as C − H···π interactions between [Mn (SB)₂(DMF)₂]³⁺ and [W (CN)₈]³⁻. An underlying net for the representation consists of two types of fragments with 1,4 M5–1 and 1,8 M9–1 topologies and further illustration of the molecular network in terms of a graph−theory approach using simplification procedure resulted in the underlying net of 2C1topological type in the complex 1 . Magnetic susceptibility measurements of complex 1 was carried out in the temperature range 2–300 K, indicates the presence of either magnetic anisotropy zero field splitting, the effect of intramolecular interactions, or both. Complex 1 follows the Curie–Weiss law with Curie constant value of 3.43 cm³mol⁻¹K, and the slight negative Weiss constant (−0.60 K) value indicates the predominant antiferromagnetic magnetic exchange interactions. The magnetic properties of Title complex was investigated thoroughly and showed that ferromagnetic interaction between W(V) and Mn (III) operate via the intramolecular H–bonding interaction between cyanide nitrogens and a hydrogen atom.     

Synthesis of several types of 2,8-dioxabicyclo[3.3.1]nonanes using amberlyst-15 as an efficient recyclable heterogeneous catalyst

A facile synthesis of 2,8-dioxabicyclo[3.3.1]nonane derivatives starting from simple molecules, such as 2-hydroxychalcones as one component and dimedone, 4-hydroxycoumarin, 2-hydroxynaphthoquinone, 2-naphthol or 1-naphthol, as the other has been achieved by use of amberlyst-15, a sulfonated polystyrene resin, as a recyclable heterogeneous catalyst. The methodology involves a domino sequence of Michael addition and two-stage cyclisation.     

Influence of the cavity size of cyclodextrins on the photochromism of azoimidazoles

1-Alkyl-2-(arylazo)imidazole (RaaiR^/) exists in trans configuration about the –NN- bond. Upon optical excitation in UV region the trans-configuration isomerises to cis-RaaiR^/. The photochromism is very susceptible to internal substituents and external environment like solvent polarity, viscosity and presence of innocent foreign species. In this work, the trans-to-cis photoisomerisation of RaaiR^/has been studied in DMF solution of cyclodextrin (α/β/γ-CD). The rate of trans-to-cis isomerisation is decreased in presence of CD compared to native form of RaaiR^/. The quantum yield of the photoisomerisation is decreased by 35–55% in inclusion phase, [email protected]^/, than free photochrome and follows the rate sequence: free state > γ-cyclodextrin > β-cyclodextrin > α-cyclodextrin. The cis-to-trans isomerisation proceeds slowly in visible light irradiation while it is appreciably fast with increasing temperature. The activation energy (E_a) of cis → trans thermal isomerisation is also diminished compared to free state of photochrome. The absorption spectral studies have been used in case of Pai-C₁₈H₃₇ with β-CD and inclusion constant is K_b ?= ?0. 121 M^?1. The ¹H NMR spectral measurement also suggests interaction of aryl protons with cavity protons of β-CD. DFT computation is also attempted to examine the inclusion of RaaiR^/with CD and the negative values of binding energy show that the process of inclusion is spontaneous and complexes formed are stable.