Facile synthesis of benzo-fused 2,8-dioxabicyclo[3.3.1]nonane derivatives via a domino Knoevenagel condensation/hetero-Diels–Alder reaction sequence

Construction of hybrid polycyclic quinolinobenzo[a]phenazinone architectures using solid-state melt reaction (SSMR)

An efficient and versatile protocol for the synthesis of hybrid polycyclic quinolinobenzo[a]phenazinones has been developed under SSMR condition via intramolecular domino Knoevenagel-hetero-Diels-Alder reaction involving the generation of two new six membered fused rings and three contiguous stereogenic centers.

A novel multicomponent quadruple/double quadruple domino reaction: highly efficient synthesis of polyheterocyclic architectures

A novel multicomponent quadruple domino reaction (MCQDR) for the assembly of structurally complex molecular architectures via the formation of three rings and three contiguous stereogenic centers has been accomplished with high regio- and diastereoselectivity. Solvents, catalysts and work-up were not required to obtain the target molecules. In addition, this new protocol is also extended for the multicomponent double quadruple domino reaction (MCDQDR) to create novel polyheterocyclic architectures in an orthogonal manner.

Applications of Friedel-Crafts reactions in total synthesis of natural products

Over the years, Friedel-Crafts (FC) reactions have been acknowledged as the most useful and powerful synthetic tools for the construction of a special kind of carbon-carbon bond involving an aromatic moiety. Its stoichiometric and, more recently, its catalytic procedures have extensively been studied. This reaction in recent years has frequently been used as a key step (steps) in the total synthesis of natural products and targeted complex bioactive molecules. In this review, we try to underscore the applications of intermolecular and intramolecular FC reactions in the total syntheses of natural products and complex molecules, exhibiting diverse biological properties.

Construction of Nitrated Benzo[3.3.1]bicyclic Acetal/Ketal Core via Nitration of o-Carbonyl Allylbenzenes

Intramolecular annulation of o-carbonyl allylbenzenes was achieved to construct novel nitrated [6,6,6]tricycles having an acetal or ketal motif in good yields. The expeditious one-step nitration route provides 4 or 5 new bond formations, including 2 or 3 C-N bonds and 2 C-O bonds. The structural framework of benzobicycle [3.3.1] is confirmed by X-ray crystallographic analysis. A plausible mechanism is proposed.

Synthesis, molecular docking and in vitro antiproliferative activity of novel pyrano[3,2-c]carbazole derivatives

A new series of polycyclic pyrano[3,2-c]carbazole derivatives were synthesized, of which three compounds displayed pronounced antiproliferative activity on cancer cells.

Coumarin heterocyclic derivatives: chemical synthesis and biological activity

This review highlights the broad range of science that has arisen from the synthesis of coumarin-linked and fused heterocycle derivatives. Specific topics include their synthesis and biological activity.

A domino synthetic approach for new, angular pyrazol- and isoxazol-heterocycles using [DBU][Ac] as an effective reaction medium

Some new, angular pyrazol- and isoxazol-heterocycles have been synthesized by the reaction of pyrazolone/isoxazolone with typical ketone-based substrates—O-alkenyloxy/alkynyloxy-acetophenones.

Recent applications of the hetero Diels–Alder reaction in the total synthesis of natural products

The synthetic utility and potential power of the Diels–Alder (D–A) reaction in organic chemistry is evident.

Synthesis of imidazo[4,5-e]thiazolo[2,3-c]-1,2,4-triazine-2,8-diones via a rearrangement of imidazo[4,5-e]thiazolo[3,2-b]-1,2,4-triazine-2,7-diones in the reaction with isatins

An aldol condensation/skeletal rearrangement protocol for the synthesis of 7-ylideneimidazo[4,5-e]thiazolo[2,3-c]-1,2,4-triazines via the reaction of imidazo[4,5-e]thiazolo[3,2-b]-1,2,4-triazines and isatins has been developed.

Catalyst-free one-pot domino reactions for selective synthesis of functionalized 2,8-oxazabicyclo[3.3.1]-nonanes and 5H-indeno[1,2-b]pyridin-5-ones

A simple and efficient method for one-pot selective synthesis of functionalized 2,8-oxazaxabicyclo[3.3.1]nonanes and hydroxy-containing 5H-indeno[1,2-b]pyridin-5-ones under catalyst-free conditions has been developed.

The first stereoselective total synthesis of neosemburin and isoneosemburin

The stereoselective total synthesis of neosemburin and isoneosemburin was achieved using 3-C-branched sugar precursors which in turn were synthesized by Claisen rearrangement of sugar derived allyl vinyl ethers.

Syntheses, X-ray structures, catalytic activity and magnetic properties of two new coordination polymers of Co(ii) and Ni(ii) based on benzenedicarboxylate and linear N,N′-donor Schiff base linkers

Mixed ligand coordination polymers showing excellent catalytic activity for Knoevenagel condensation reaction.

Catalyst-controlled regio- and stereoselective synthesis of diverse 12H-6,12-methanodibenzo[d,g][1,3]dioxocines

Regio- and stereoselective synthesis of 12H-6,12-methanodibenzo[d,g][1,3]dioxocines has been accomplished by the EDDA and PTSA-catalyzed cascade reactions of resorcinols and 2-hydroxychalcones.

Highly regio- and stereoselective Diels-Alder cycloadditions via two-step and multicomponent reactions promoted by infrared irradiation under solvent-free conditions

Infrared irradiation promoted the Diels-Alder cycloadditions of exo-2-oxazolidinone dienes 1-3 with the Knoevenagel adducts 4-6, as dienophiles, leading to the synthesis of new 3,5-diphenyltetrahydrobenzo[d]oxazol-2-one derivatives (7, 9, 11 and 13-17), under solvent-free conditions. These cycloadditions were performed with good regio- and stereoselectivity, favoring the para-endo cycloadducts. We also evaluated the one-pot three-component reaction of active methylene compounds 20, benzaldehydes 21 and exo-2-oxazolidinone diene 2 under the same reaction conditions. A cascade Knoevenagel condensation/Diels-Alder cycloaddition reaction was observed, resulting in the final adducts 13-16 in similar yields. These procedures are environmentally benign, because no solvent and no catalyst were employed in these processes. The regioselectivity of these reactions was rationalized by Frontier Molecular Orbital (FMO) calculations.

Total synthesis of diptoindonesin G via a highly efficient domino cyclodehydration/intramolecular Friedel-Crafts acylation/regioselective demethylation sequence

A highly efficient total synthesis of diptoindonesin G is described employing a domino dehydrative cyclization/intramolecular Friedel-Crafts acylation/regioselective demethylation reaction of aryloxyketone 7 by the action of BCl(3) wherein the tetracyclic 6H-anthra[1,9-bc]furan-6-one skeleton was constructed via the 3-arylbenzofuran in a one-pot manner. This is the first example of the strategic combination of these three reactions in a cascade fashion. The routes presented here allow for direct access to diptoindonesin G and its analogues.

L-proline-catalysed facile green protocol for the synthesis and antimycobacterial evaluation of [1,4]-thiazines

A series of ethyl 6-(4-chlorobenzoyl)-1,1-dioxo-3,5-diaryl-1,4-thiazinane-2-carboxylates was prepared in good yields (72-90%) from the reaction of ethyl 2-[(2-oxo-2-arylethyl)sulfonyl]acetate, substituted aromatic aldehydes and amines in presence of green catalyst, L-proline. These compounds were evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB), multi-drug resistant M. tuberculosis (MDR-TB) and Mycobacterium smegmatis (MC(2)) using agar dilution method. Ethyl 6-(4-chlorobenzoyl)-3,5-di(4-nitrophenyl)-1,1-dioxo-1,4-thiazinane-2-carboxylate was found to be the most promising compound (MIC: 0.68 microM) active against MTB and MDR-TB.