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A novel and efficient four component reaction involving diketene, primary amines, aromatic aldehydes and 2-amino-benzimidazole in the presence of I2 in refluxing EtOAc for the synthesis of benzo[4,5]imidazo[1,2-a]-pyrimidine-3-carboxamides is reported. Good yields, mild reaction conditions and facile isolation of products in pure forms are advantageous of this methodology.

A facile, efficient and un-catalyzed approach for the synthesis of new symmetrical highly- substituted indeno [1,2-b]pyrrole derivatives through four-component reaction, involving, primary amines, diamine, diketene, and ninhydrin in CH2Cl2 at ambient temperature is reported. This approach enjoys merits such as being done in the absence of catalyst at ambient temperature, giving good to excellent yields, completed in short reaction times, and showing a wide functional group tolerance. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Novel and efficient multicomponent reactions (MCRs) involving diketene, ninhydrin (indane-1,2,3-trione) and one primary amine (3CR) or two different primary amines (4CR) were achieved for the successful synthesis of dihydro-4H-indeno[1,2-b]furan-3-carboxamides or tetrahydroindeno[1,2-b]pyrrole-3-carboxamides, respectively. The merits of this method are highlighted by using either commercially available or easily accessible starting materials, operational simplicity, facile workup procedure, efficient usage of all the reactants, tolerance of a variety of functional groups and ability to conduct under un-catalyzed reaction condition. The products were also isolated by just decantation of the solvent, and for the purification column chromatography was non-required.

Catalytic behavior of perchloric acid when supported to mesoporous silica SBA-15 (SBA-15/HClO4) was investigated as a heterogeneous Bronsted acid. Its reactivity and leaching possibility were studied in cascade ring opening-cyclocondensation sequence of diketene and alcohol with aldehyde in the presence of either of urea or ammonium acetate. Results showed that this catalyst can be highly recyclable for several cycles.

A one-pot pseudo five-component reaction for the synthesis of 2-aryl-4-hydroxy-4-methyl-6-oxo-N 1,N 3-dialkylcyclohexane-1,3-dicarboxamide derivatives involving different primary amines, various aromatic aldehydes, and diketene in the presence of triethylamine with high yields is achieved.

(E)-5-[1-(4-Phenyl-2-oxo-1-oxaspiro[4.5]dec-3-en-3-yl)eth­yl­idene]-2-aminoimidazolin-4-one derivatives, as novel fungicidal agents, are designed and synthesized in moderate to excellent yields in four steps from (1-hydroxycyclohexyl)(phenyl)methanone and diketene as the starting materials. The products are characterized by 1H NMR and HRMS (ESI) analysis. An in vivo bioassay shows that some of the products exhibit good to excellent inhibition against P. cubensis and C. lagenarium, whilst up to 94.7% inhibition against P. capsici and up to 78.1% inhibition against B. cinerea is demonstrated in the in vitro bioassay. EC50 values of 3.40 and 5.86 μg/mL are demonstrated against P. capsici and B. cinerea.

The novel fungicidal agents, (E)-5-[1-(2-oxo-1-oxaspiro[4,5]dec/non-3-en-3-yl)ethylidene]-2-aminoimidazolin- 4-one derivatives, were designed and synthesized in moderate to excellent yields in four steps using α-hydroxyketone and diketene as raw materials and characterized by HR-ESI-MS, 1H NMR and X-ray diffraction. The preliminary bioassay showed that some of these compounds, such as 5e, 6a, 6e, and 7 h exhibit 87.8%, 91.3%, 89.9% and 87.8% inhibition rates against Sclerotinia scleotiorum, 3b, 3c, 4c and 7 h exhibit 96.4%, 92.5%, 90.3% and 76.9% inhibition rates against Phytophthora capsici at the concentration of 50 µg/mL, respectively. These compounds exhibited significant fungicidal activities against S. scleotiorum and P. capsici with EC50 values of 2.56–11.60 µg/mL, and compounds 6e and 7 h exhibited weak inhibition against the spore germination of S. scleotiorum, while the spore germination of P. capsici was strongly inhibited by compound 7 h solution. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation indicated that compound 7 h had a significant impact on the structure and function of the hyphal cell wall of P. capsici mycelium.

Density functional theory (DFT) calculations have been performed to unravel the mechanism of Lewis-acid-induced Ni(cod)2-catalyzed selective coupling reactions of one diketene and two alkynes. Complex mixtures (unsymmetrical phenylacetic acid P1, symmetrical phenylacetic acid P2 and (3E)-4-ethyl-5-methylene-3-heptenoic acid P3) were obtained in the absence of Et2Al(OEt). P1 formation involves C(sp2)-O oxidative addition of diketene, twice alkyne insertion, intramolecular C═C insertion, acidolysis, and β-H elimination. For P2/P3 formation, the common key issue related to the C═C double bond cleavage of the substrate diketene was explored and found that it was accomplished via a four-membered-ring-closure/four-membered-ring-opening process. And then, P2 was produced via the second alkyne insertion while P3 was accessed by a stoichiometric reaction with HCl. The Et2Al(OEt)-induced chemoselectivity was also probed. It is found that the Ni–O (from Al reagent) bonding facilitates the second alkyne insertion, an...

The supplementation of exogenous antioxidants to scavenge excessive reactive oxygen species (ROS) is an effective treatment for cerebral ischemia-reperfusion injury (CIRI) in stroke. Piperlongumine (PL), a natural alkaloid, has a great potential as a neuroprotective agent, but it also has obvious toxicity. Moreover, its neuroprotective effects remain to be improved. In this study, we designed a series of novel PL analogs by hybridizing the screened low-toxicity diketene skeleton with antioxidant effect and the 3,4,5-trimethoxyphenyl group, which may increase the antioxidant activity of PL. The intermediate was synthesized by a novel green synthesis method, and 34 compounds were obtained. The compounds without obvious cytotoxicity have remarkable antioxidant effects, especially compared with diketene skeletons and PL. The cytoprotection of the active compound decreased significantly by reduction of the carbon-carbon double bonds of the Michael acceptor in the diketene skeleton. More importantly, further study revealed that compound A9, which has the best activity, can confer protection for cells against oxidative stress and attenuate brain injury in vivo. Overall, this study provided a promising drug candidate for the treatment of CIRI and guided the further development of drug research in oxidative stress-mediated diseases.

A versatile and economical reaction of diketene (1), aryl amines 2, cyclic 1,3-diketones 3, primary amines 4, and aryl aldehydes 5 was explored to synthesize 3,4-dihydropyran-3-carboxamide derivatives under mild conditions. Three stereogenic centers are generated in the products, and the structure of the major diastereomer of 6{1,1,3,1} was identified by X-ray diffraction and 2D NMR spectroscopy. The scope and limitation investigation provided two series of (2S,3R,4S)-chromene-3-carboxamides in good to excellent yields with high diastereoselectivity. Two products, 6{5,3,1,1} and 6{7,3,1,1}, exhibited in vitro anti-inflammatory activity with significant inhibition of pro-inflammatory cytokine IL-6 and TNF-α expression in lipopolysaccharide (LPS)-treated Raw 264.7 cells.

ESI-protonated natural curcumin (1) undergoes gas-phase cyclization and dissociates via competitive expulsions of 2-methoxy phenol and C(4)H(4)O(2) (diketene or an isomer). Evidence from mechanistic mass spectrometry and from Density Functional Theory (DFT) reveals that a two-step sequential cyclization occurs for the protonated molecule prior to the unusual loss of the elements of 2-methoxy phenol. Furthermore, the presence of the methoxy group at postion-3 is essential for the second cyclization. The transformation of curcumin upon protonation in the gas phase may be predictive of its solution chemistry and explain how curcumin plays a protective role in biology.

The pure rotational spectrum of diketene has been studied in the millimeter-wave region from ∼240 to 360 GHz. For the ground vibrational state and five vibrationally excited satellites (ν24, 2ν24, 3ν24, 4ν24, and ν16), the observed spectrum allowed for the measurement, assignment, and least-squares fitting a total of more than 10 000 distinct rotational transitions. In each case, the transitions were fit to single-state, complete or near-complete sextic centrifugally distorted rotor models to near experimental error limits using Kisiel’s ASFIT. Additionally, we obtained less satisfactory least-squares fits to single-state centrifugally distorted rotor models for three additional vibrational states: ν24 + ν16, ν23, and 5ν24. The structure of diketene was optimized at the CCSD(T)/ANO1 level, and the vibration–rotation interaction (αi) values for each normal mode were determined with a CCSD(T)/ANO1 VPT2 anharmonic frequency calculation. These αi values were helpful in identifying the previously unreported ν1...

Hyperforin has remained a popular and challenging synthetic target since its isolation over forty years ago. As a result, numerous synthetic strategies and ring-forming reactions have been developed to address its formidable molecular architecture. Herein we describe our contributions to this area resulting in a ten-step synthetic pathway enabled by a novel diketene annulation reaction and oxidative ring expansion strategy.

Several novel chiral Schiff base ligands were prepared from a commercially available chloramphenicol base and applied to the titanium-mediated asymmetric aldol reaction of diketene with various α,β-unsaturated aldehydes. This reaction proceeded in good yield with high enantioselectivity. The synthetic utility of this methodology was demonstrated in the short synthesis of atorvastatin calcium.

Diketene is an ideal molecule for use in many organic transformations, since it possesses electrophilic and nucleophilic sites which react with numerous functional groups. Diketene is mostly used as the common starting material for structurally diverse mono-, spiro-, and fused six-membered heterocycles such as lactones, pyrans, pyridines, quinolines, isoquinolines, oxazine, quinoxalines, benzothiazinone, 1,4-thiazidines, and oxazinonethione.

The novel fungicidal agents 5-(5,5-dimethylbutenolide-3-ethylidene)-2-amino-imidazolinone derivatives, were designed and synthesized in moderate to excellent yields in four steps by αa-hydroxyketone and diketene as raw materials and characterized by HR-ESI-MS and 1H-NMR. The preliminary bioassay showed that some of these compounds, such as 4a, 4e and 5g exhibit 94.9%, 92.8% and 81.4% inhibition rates against Sclerotinia scleotiorum at the concentration of 50 µg/mL, respectively. The EC50 values of compounds 4e and 4i were 4.14 and 3.27 µM against Alternaria Solani, and 5g had EC50 value of 3.23 µM against S. scleotiorum. Compounds 4d and 4g displayed 98.0% and 97.8% control of spore germination against Botrytis cinerea at the concentration of 100 µg/mL, respectively.

This review highlights the methods used for the synthesis of 3-oxo-N-(pyridin-2-yl)butanamide compounds. The reactivity and synthetic importance are investigated. In this context, recent progress in the synthesis and use of 3-oxo-N-(pyridin-2-yl)butanamide as precursors for heterocyclic compounds is reviewed. The synthetic routes for preparation of 3-oxo-N-(pyridin-2-yl)butanamide are based on the reaction of diketene with aromatic primary amine and reaction of 2-aminopyridine with β-keto-t-butylthioester or ethylacetoacetate. The bibliography includes 73 references.

A novel five-component strategy involving commercially available diketene, primary amines, malononitrile and various benzaldehydes for the synthesis of densely functionalized 1,4-dihydropyridines in good yields was achieved. The reaction pathway involves a sequential ring-opening of diketene/enamine formation/Knoevenagel-condensation/Michael addition and 6-exo-tet cyclization, resulting in multiple bond-formation events including two C–C and three C–N bonds ultimately leading to the formation of the respective 1,4-dihydropyridines.

4-Methyleneoxetan-2-one (Diketene or DK) consists of a four-membered lactone ring adjacent to a methylene function. It can be used as a versatile precursor for the syntheses of wide range of heterocycles including fused and spiral biheterocycles. In this chapter, we try to cover the structural features and reactivity of DK, and underscore its applications as a flexible and useful synthon in the syntheses of four- and five-membered heterocycles as well as a wide variety of fused or spiro heterocycles. This chapter as part 1 is divided in accordance with the ring sizes and subdivided according to types, numbers, and arrangements of heteroatoms.

Hyperforin has remained a popular and challenging synthetic target since its isolation over forty years ago. As a result, numerous synthetic strategies and ring-forming reactions have been developed to address its formidable molecular architecture. Herein we describe our contributions to this area resulting in a ten-step synthetic pathway enabled by a novel diketene annulation reaction and oxidative ring expansion strategy.

International audience; As an alternative to recombinant virus, synthetic carriers are widely developed for providing efficient and safe DNA delivery. To reach the nucleus where nucleic acid (NA) constructs are transcripted, chemical complexes have to overcome serious cellular traps such as endosomal escape and intracellular trafficking. Here, the design and the multi-step synthesis of a stabilizing tetraether lipid analogue of archaeal counterparts containing a diorthoester moiety in the middle of the bridging chain were described. The key step involved a double coupling reaction between two diether alcohols and a diketene acetal. Under aqueous acidic conditions, the diorthoester function of the tetraether lipid can be hydrolysed to yield two monopolar diether lipids. Applied to gene delivery in association with a cationic lipid, this new helper bipolar tetraether lipid led to lipid-DNA complexes with sizes and potential zeta values depending on the charge ratios (+/-). In addition, preliminary in vitro transfection assays supported the interest of these novel bipolar lipid-based lipoplex formulations compared to standard Lipofectamine-based formulations. © 2016 Elsevier Ltd. All rights reserved.

This review highlights the methods used for the synthesis of 3-oxo-N-(pyridin-2-yl)butanamide compounds. The reactivity and synthetic importance are investigated. In this context, recent progress in the synthesis and use of 3-oxo-N-(pyridin-2-yl)butanamide as precursors for heterocyclic compounds is reviewed. The synthetic routes for preparation of 3-oxo-N-(pyridin-2-yl)butanamide are based on the reaction of diketene with aromatic primary amine and reaction of 2-aminopyridine with β-keto-t-butylthioester or ethylacetoacetate. The bibliography includes 73 references.

The remarkably efficient synthesis of biologically relevant diazepines, diazocines, and diazonines is also performed using conventional heating instead of microwave irradiation with virtually identical product yields after slightly longer reaction times.

A nickel catalyst promotes the multicomponent coupling reaction of diketene, an alkyne, and Me2Zn to provide 3-methylene-4-hexenoic acids in excellent yields. Under similar conditions, the combination of the nickel catalyst and Et2Al(OEt) promotes a cycloaddition reaction involving dimerization of an alkyne to furnish phenylacetic acids. In the presence of PPh3, a formal [2+2+1+1] cycloaddition reaction proceeds to afford regioisomeric phenylacetic acids via cleavage of the CC bond.