Biarylmethane and Fused Heterocyclic Arene Synthesis via in Situ Generated o- and/or p-Naphthoquinone Methides

Access to Naphthoic Acid Derivatives through an Oxabenzonorbornadiene Rearrangement

Herein, the synthesis of 1-hydroxy-2-naphthoic acid esters through an unexpected Lewis-acid-mediated 1,2-acyl shift of oxabenzonorbornadienes is reported. Using this methodology, novel substitution patterns for 1-hydroxy-2-naphtoic acid esters can be obtained. A mechanistic proposal and rationale for this transformation, the products of which had been previously incorrectly characterized, is given.

Synthesis of Dihydrobenzofuro[3,2-b]chromenes as a potential 3CLpro inhibitors of SARS-CoV-2: A molecular docking and dynamics simulation study

The recent emergence of pandemic of coronavirus (COVID‐19) caused by SARS‐CoV‐2 has raised significant global health concerns. More importantly, there is no specific therapeutics currently available to combat against this deadly infection. The enzyme 3‐chymotrypsin‐like cysteine protease (3CLpro) is known to be essential for viral life cycle as it controls the coronavirus replication. 3CLpro could be a potential drug target as established before in the case of severe acute respiratory syndrome coronavirus (SARS‐CoV) and Middle East respiratory syndrome coronavirus (MERS‐CoV). In the current study, we wanted to explore the potential of fused flavonoids as 3CLpro inhibitors. Fused flavonoids (5a,10a‐dihydro‐11H‐benzofuro[3,2‐b]chromene) are unexplored for their potential bioactivities due to their low natural occurrences. Their synthetic congeners are also rare due to unavailability of general synthetic methodology. Here we designed a simple strategy to synthesize 5a,10a‐dihydro‐11H‐benzofuro[3,2‐b]chromene skeleton and it's four novel derivatives. Our structural bioinformatics study clearly shows excellent potential of the synthesized compounds in comparison to experimentally validated inhibitor N3. Moreover, in‐silico ADMET study displays excellent druggability and extremely low level of toxicity of the synthesized molecules. Further, for better understanding, the molecular dynamic approach was implemented to study the change in dynamicity after the compounds bind to the protein. A detailed investigation through clustering analysis and distance calculation gave us sound comprehensive data about their molecular interaction. In summary, we anticipate that the currently synthesized molecules could not only be a potential set of inhibitors against 3CLpro but also the insights acquired from the current study would be instrumental in further developing novel natural flavonoid based anti‐COVID therapeutic spectrums.

Systematic Study of Aromatic-Ring-Targeted Cycloadditions of 5-Hydroxymethylfurfural Platform Chemicals

The reaction space of the furanics-to-aromatics (F2A) conversion process for 5-hydroxymethylfurfural (HMF)-based platform chemicals has been explored both experimentally and by quantum chemistry methods. For the first time, a structure-activity relationship was established in furan-yne cycloaddition for a number of different HMF derivatives. Correlations between the activation energy of the cycloaddition stage and the structure of the substrates were established by molecular modeling methods. Analysis of the concerted and stepwise mechanisms of cycloaddition in the singlet and triplet electronic states of the molecular system was carried out. A series of biobased 7-oxanorbornadienes was obtained in the reaction with dimethyl acetylenedicarboxylate. Various methods of aromatization of the obtained [4+2] adducts have been examined. Rearrangement catalyzed by a Lewis acid leads to the formation of a phenol derivative, whereas reduction by diiron nonacarbonyl leads to the formation of functionalized benzene. Systematic study of the cycloaddition process has revealed a simple way to analyze and predict the relative reactivity of furanic substrates.

Allylsilane Reagent-Controlled Divergent Asymmetric Catalytic Reactions of 2-Naphthoquinone-1-methide

Herein, the first allylsilane reagent-controlled divergent asymmetric Hosomi-Sakurai conjugate allylation and hetero-Diels-Alder (HDA) with 2-naphthoquinone-1-methide (2-Nap-Q-1-M) under the catalysis of Sc^III /Feng ligand complex is reported. With these methods, a variety of uniquely substituted chiral allyl-functionalized diaryl compounds and naphthopyran products were obtained in a straightforward and highly stereoselective (up to 96.5:3.5 e.r.) manner under mild conditions. Moreover, it is demonstrated that 2-Nap-Q-1-M can serve as an efficient diene for a side asymmetric Diels-Alder (D-A) reaction. This principle can provide a straightforward access to hydrophenalene in an optically active form, which represents a structural core of various natural products and bioactive molecules.

1,4-Addition of o-naphthoquinone methides induced by silver-catalyzed cyclization of enynones: an approach to unsymmetrical triarylmethanes and benzo[f]chromenes

The 1,4-addition reaction of ortho-naphthoquinone methide (o-NQM) intermediates induced by silver-catalyzed ring formation with electron-rich aromatic compounds and α-methylene ketones has been developed.

A Strategy To Obtain o-Naphthoquinone Methides: Ag(I)-Catalyzed Cyclization of Enynones for the Synthesis of Benzo[ h]chromanes and Naphthopyryliums

A new strategy to obtain o-NQM intermediates through a ring-formation strategy by Ag(I)-catalyzed cyclization of 2-alkenylphenyl alkynyl ketones and its [4 + 2] annulations with styrenes has been developed. This reaction features high efficiency, mild reaction conditions, as well as flexible substitutions and atom economy. The obtained benzo[ h]chromane products were further oxidized to naphthopyryliums, which displayed tunable photophysical properties.

Asymmetric organocatalytic synthesis of chiral 3,3-disubstituted oxindolesviaa 1,6-conjugate addition reaction

The chiral spirocyclic phosphoric acid-catalyzed enantioselective 1,6-conjugate addition reaction ofpara-quinone methides derived fromN-unprotected isatins with indoles was developed.

Aromatic aldehyde-selective aldol addition with aldehyde-derived silyl enol ethers

Unprecedented chemoselectivity between aromatic and aliphatic aldehydes has been achieved in the Mukaiyama aldol reaction using aldehyde-derived silyl enol ethers.

Phosphine-catalyzed Friedel–Crafts reaction of naphthols with para-quinone methides: expedient access to triarylmethanes

A novel phosphine-catalyzed Friedel–Crafts reaction of naphthols with para-quinone methides has been developed.

Synthetic transformation of 1,3-diarylisobenzofuran-DMAD adducts: a facile preparation of tri-substituted α-naphthols

1,3-Diarylisobenzofuran-DMAD adducts upon reaction with BF₃·OEt₂ in DCM at room temperature underwent a regiospecific 1,2-aryl migration followed by the Krapcho decarboxylation to give tri-substituted α-naphthols in good yields.