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[Display omitted] A simple yet efficient approach towards the synthesis of β -hydroxy selanylated ketones was developed from easily accessible chalcones and diphenyl diselenide through an electrochemical pathway. In this technique, diphenyl diselenide and water are the source of PhSe. and hydroxyl (–OH) groups that can be inserted at the α and β positions respectively producing β -hydroxy selanylated ketones in moderate to good yields. The reaction features difunctionalization of ketones, catalyst free, mild reaction conditions, stereo and regioselectivity in an undivided electrochemical cell at room temperature. For this transformation, a plausible radical mechanism has been put out. [ABSTRACT FROM AUTHOR]

Abstract 1,6-Conjugate addition of various carbon nucleophiles to p -quinone methide surrogate is reported. The active methylene containing C -nucleophiles such as 1,3-diketones, diesters and ketoesters underwent two consecutive additions leading to bis-addition products, diarylpropanes. Whereas, nitroalkanes proceeded to contribute mono-addition products. Surprisingly, bromo analogue of p -quinone methide surrogate underwent halophilic dimerization reaction with excellent yield. The reported strategy provides an efficient synthesis of 1,3-diarylpropane derivatives bearing pharmacophoric ortho -methoxy phenol moiety under mild reaction conditions. Graphical abstract Image 1 Highlights • Two consecutive 1,6-conjugate additions of carbon nucleophiles to p -quinone methide surrogate is reported. • This strategy was found amenable to 1,3-ketoesters, diesters, diketones and nitroalkane compounds. • Wide substrate scope and good to excellent yields are reported under mild reaction conditions. • It is a novel strategy for the synthesis of 1,3-diarylpropanes bearing pharmacophoric ortho -methoxy phenol moiety. • Formation of an unexpected dimerized product through a halophilic reaction is reported. [ABSTRACT FROM AUTHOR]

We herein report a serendipitously observed acid mediated rearrangement of monoethylene ketal of 2-methyl-2-(3-methylbut-2-en-1-yl)cyclohex-4-ene-1,3-diones to Dihydrobenzopyran and demonstrated the application of this methodology in the construction of core carbon scaffolds of dimethoxyajacareubin, cariphenone-A and crotamadine. [ABSTRACT FROM AUTHOR]

An efficient protocol for the synthesis of dihydrobenzoxazine and tetrahydrobenzoxazepine derivatives has been developed using haloarenes involving N -dealkylative S N Ar reaction. The method employs a wide variety of substrates and features the formation of C O and C N bonds in one-pot fashion. The products thus generated have been further transformed to m -terphenyls by using Suzuki coupling reaction. [ABSTRACT FROM AUTHOR]

1,6-Conjugate addition of variety of amines and phenols to cyclohexadienone derivative 1 directly leading to aryl benzyl amines and aryl benzyl ethers in excellent yield has been reported. The reaction proceeds via a sequential Michael type addition followed by aromatization. This methodology allows a facile and efficient synthesis of functionalized aryl benzyl amines and aryl benzyl ethers under mild conditions. [ABSTRACT FROM AUTHOR]

A new role of superoxide ion in the isomerization of homobenzylic acetylenes leading to 1-aryl-1,3-butadienes is reported. The unconventional reagent KO 2 is found to be superior in performing this kind of isomerization over other the commonly used bases. For substrates containing arene moiety and triple bond connected through more than two methylene groups, and for propargylcyclohexanol the reagent selectively effected migration of the triple bond. Reactivity of KO 2 towards the substrates having disubstitution at benzylic position varied depending on the nature of the substitution, alkyl-substitution lead to isomerization to give mixture of allene (an intermediate in the isomerization of acetylene to 1,3-butadiene) and triple bond migration product; whereas phenyl-substituted compound gave 1,3-diene. The utility of the methodology was demonstrated through a Diels–Alder reaction of one of the dienes obtained by the isomerization with suitable dienophiles. [ABSTRACT FROM AUTHOR]

A facile and efficient base promoted one-pot dimerization of halo cyclohexene derivatives leading to a de novo synthesis of biologically important diarylmethane and diarylmethanone derivatives is reported. A plausible mechanism for the unexpected formation of the title compounds involves dehydrohalogenation, 1,6-conjugate addition, subsequent aromatization through C–C bond cleavage and dehydrohalogenation. [ABSTRACT FROM AUTHOR]

An efficient and versatile synthesis of 3-alkenylbutenolides through direct Suzuki–Miyaura cross coupling reaction between preformed 3-halobutenolides and a range of readily accessible boronic acids has been devised. The coupling process exhibits good functional group compatibility and is preparatively viable. The methodology has been applied to achieve short syntheses of natural products rac -akolactones A & B and rac -hamabiwalactone B. The scope of the Suzuki–Miyaura reaction based protocol has been further amplified through the synthesis of 3,3′-alkenyl- bis -butenolides by employing α, ω- bis -boronic acids as coupling partners and applied to a synthesis of bioactive natural product rac -ancepsenolide. [ABSTRACT FROM AUTHOR]

A macrocyclic furanobutenolide was crafted from readily available furan building-blocks to set-up a transannular Diels–Alder reaction which delivered the carbocyclic core present in a class of cembranoid diterpene natural products. [ABSTRACT FROM AUTHOR]

Total syntheses of two antimicrobial natural products (±)-cis-neocnidilide and (±)-trans-neocnidilide starting from a readily preparable cyclohexa[b]-fused 5-oxabicyclo[2.1.1]hexane derivative are presented. The diastereomeric tetrahydrofuran tricarboxylate epimers obtained from a BF3⋅OEt2 promoted Grob-type fragmentation of the oxa-bicycle derivative were converted into title natural products by employing pyridinium dichromate/acetic anhydride mediated bis-oxidative cleavage reaction. [ABSTRACT FROM AUTHOR]

Abstract: A formal synthesis of marine-derived antitumor natural product varitriol from a 5-oxabicyclo[2.1.1]hexane derivative is described. A tetrahydrofuran unit of varitriol embedded with four contiguous stereocenters was synthesized with an overall yield of 10.2% in 11 steps from an oxa-bicyclic system. An unprecedented oxidative cleavage reaction involving scissoring of two C C bonds at oxa-quaternary carbon of THFs leading to γ-butyrolactones was reported and a plausible mechanism has been proposed. [Copyright &y& Elsevier]

Abstract: Acid mediated, efficient Grob-type fragmentation reaction facilitated by vicinal ketal and ester moieties in variety of 5-oxabicyclo[2.1.1]hexanes leading to the corresponding annulated and 2,2,5-trisubstituted tetrahydrofurans is reported. Among the Brønsted and Lewis acids tested, BF3·OEt2 appears to give the best results, furnishing near quantitative yield (>99%) of tetrahydrofuran tricarboxylate derivatives under mild reaction condition. In case of unsymmetrical monosubstituted 5-oxabicyclo[2.1.1]hexanes two regioisomeric products are obtained. A strategy to transform one of the ester groups of the title compounds to protected hydroxymethyl moiety was evolved, which allows access to differentially protected 2-hydroxymethyl THF derivatives upon fragmentation. Employing TiCl4/R or S-BINOL as chiral Lewis acid, an enantioselective fragmentation (up to 66% ee) was described for the meso bis-furan derivative. [Copyright &y& Elsevier]

Abstract: A total synthesis of bioactive tetracyclic natural product paracaseolide A, embodying an architecturally unusual oxa-bowl framework, has been accomplished from commercially available 5-methyl-2-furfural. The key step involving a thermal [4+2]-dimerization of an appropriately crafted 5-methyl-3-alkenylbutenolide is shown to proceed in a stepwise manner. [Copyright &y& Elsevier]

Abstract: Several symmetrical, linear dimers and some star-like tetramers were prepared using easily accessible oxa-bridged derivatives as central rigid cores. In order to produce new liquid crystalline materials various mesogenic/promesogenic groups, containing biphenyl-4,4′-diol, 4,4′-(diazene-1,2-diyl)diphenol and cholesterol sub-moieties, were connected through oxy-ethylene linkers via an ester linkage, in the end-on fashion. Their thermal behaviour and mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarized optical microscope (POM), and variable temperature small-angle X-ray diffraction (XRD) methods. While essentially all the biphenyl-4,4′-diol- and 4,4′-(diazene-1,2-diyl)-based dimeric derivatives exhibited smectic liquid crystalline mesophases, the nature of which are mesogenic groups dependent, none of the cholesterol-containing compounds and tetramers were mesomorphic. [ABSTRACT FROM AUTHOR]

Abstract: A facile transformation of pentasubstituted tribromophenol derivatives to the corresponding alkyl-substituted dibromo-p-benzoquinones has been achieved using PbO2 as oxidizing agent in combination with 60% aq HClO4 in acetone in 70–72% yields. The electrochemical properties of these quinones were studied by means of cyclic voltammetry and compared with p-benzoquinone (BQ) and 2,3-dichloro-5,6-dicyano-benzoquinone (DDQ) recorded under identical experimental conditions. [Copyright &y& Elsevier]

Abstract: Nucleophilic racemic amines have been synthesized utilizing a C7nC5x free-radical cascade reaction from a bis-allyl amine starting material. Being potentially useful organocatalytic bases as is evident from their screening in the Baylis–Hillman reaction, optically pure amines were also synthesized from optically pure aldehydes (−) or (+)-4. Bis-allyl amides under similar radical reaction condition resulted in C7n cyclized products. [Copyright &y& Elsevier]

Abstract: Palladium(II)-catalyzed oxidative cyclization of methyl 2-allyl-4,5,6-tribromo-3-hydroxybenzoate 4 gave a mixture of methyl 5,6,7-tribromo-2-methyl-benzofuran-4-carboxylate 5 and methyl 6,7,8-tribromo-2H-1-benzopyran-5-carboxylate 6; the ratio of the two products varied between 71:29 and 24:76 depending on the reaction conditions. On the other hand, NBS or NIS mediated cyclization of 4 followed by treatment with NaOMe or DBU furnished benzofuran derivative 5 in good overall yield. [Copyright &y& Elsevier]

Abstract: An efficient stereoselective synthesis of both the diastereomers of diquinane-based conformationally constrained symmetric bis-γ-lactones starting from tricyclic derivative 9 is reported. The key step involves the intramolecular ring opening of an epoxide by the in situ formed hydrate of a diketone leading to the tetracyclic hemiacetal 10, which directly leads to the exo-hydroxy bis-γ-lactone derivatives 2 and 4 under basic hydrogen peroxide cleavage conditions. Conversion to the endo-hydroxy bis-γ-lactone derivatives 1 and 3 was accomplished through lithium hydroxide mediated SN2 displacements in dimesylate 7, or more expeditiously, via trimesylate 21 through alkaline H2O2 mediated cleavage. [Copyright &y& Elsevier]

Abstract: A new reaction of diazomethane with norbornyl α-diketones in MeOH as solvent leading regioselectively to ketals is described. The mechanistic details of this intriguing reaction were investigated employing d 4-MeOH, EtOH and d 6-EtOH. The surprising observation of complete deuterium incorporation in the diazomethane-derived methoxy group was accounted for by sequential deuterium exchange between the initially formed hemiketal d 4-18 and diazomethane in the presence of d 4-MeOH as solvent. [Copyright &y& Elsevier]

Knoevenagel condensation proceeds efficiently in recyclable [bmim]PF6 and [bmim]BF4 without any catalyst, and hydrotalcites in ionic liquid serve as a safe and recyclable reaction system for both Knoevenagel as well as nitroaldol condensations. [Copyright &y& Elsevier]

Nitroarenes were chemoselectively reduced to the corresponding amines using zinc and aqueous ammonium salts in ionic liquids as a safe and recyclable reaction medium. Our results specify the effect of ammonium salts in the process; the combination of Zn/NH4Cl in [bmim][PF6] or Zn/HCO2NH4 in [bmim][BF4] were the suitable conditions for the reduction of nitroarenes. Azobenzenes were also smoothly reduced to hydrazobenzenes with Zn/HCO2NH4 (aq.) in recyclable [bmim][BF4] without any over reduction to the corresponding anilines. [Copyright &y& Elsevier]

• FeCl 3 catalyzed C C, C N bond formation between methyl enol ethers and anilines. • 2,3-Disubstituted indole formation via aryl group migration. • Anilines act as bis-nucleophiles. An intermolecular FeCl 3 catalyzed reaction between anilines and enol ethers is described. A variety of enol ethers and aromatic amines undergo a C C bond formation followed by cyclization via C N bond formation to afford the 2,3-disubstituted indoles, involving an unexpected aryl group migration. In this methodology, anilines act as bis-nucleophiles, wherein the initial attack occurs at the α-position of enol ether from the ortho position of aniline followed by the subsequent reaction of the amine moiety of aniline at the β-position, leading to the indole framework. This method is simple, obviates the use of expensive/hazardous transition-metal catalysts, and offers a wide range of substrate scope. [ABSTRACT FROM AUTHOR]

Abstract: A two-step synthesis of marine origin brominated alkaloids wilsoniamines A (1) and B (2), isolated from Australian bryozoan Amathia wilsoni Kirkpatrick, possessing a novel hexahydro-1H-pyrrolo[1,2-c]imidazol-1-one ring system is described. The core hexahydro-1H-pyrrolo[1,2-c]imidazol-1-one ring systems is constructed through a condensation reaction between (2,4,6-tribromo-3-methoxyphenyl)acetaldehyde and (S)-N-methylpyrrolidine-2-carboxamide as key steps. The orientation of substituted benzyl side-chain in the two epimeric natural products was controlled by carrying out the key condensation reaction under kinetic or thermodynamic conditions. [Copyright &y& Elsevier]

Abstract: A simple protocol for the synthesis of an aesthetically pleasing ‘oxa-basket’ (5-methoxy-2,8,13-trioxapentacyclo[7.2.1.1.5,120.4,1106,10]tridecane-3,7-dione), possessing 9-oxa-noradamantane core, is described. The readily available diquinane based dichloro bis-γ-lactone precursor upon treatment with MeSO3H furnished dichloro ‘oxa-basket’ which was dechlorinated using TBTH/AIBN to obtain the title compound. The key role of the chlorines was demonstrated by replacement with hydrogen or allyl substituents which redirects the cascade to simple hydrolysis products. [Copyright &y& Elsevier]

Abstract: A simple and useful protocol for the reduction of nitro arenes to their corresponding azoxy derivatives by employing zinc and NH4Cl in a mixture of [bmim][BF4] and water is described. The selective reduction of nitro to azoxy is attributed to the hitherto unknown moderating effect of oxygen on zinc metal. [Copyright &y& Elsevier]

Abstract: Synthesis of a compound with bowl-like, symmetrical molecular architecture, starting from a Diels–Alder adduct 7, derived from a reaction between 2,5-dihydro-2,5-dimethoxyfuran and 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene, is reported. [Copyright &y& Elsevier]

• Brønsted acid-induced one-pot synthesis of 2-methylbenzofurans. • Construction of new C–O bond formation via an efficient Grob-type fragmentation. • Halobenzofurans were successfully utilized to synthesis 6,7-bisaryl benzofurans. An efficient Brønsted acid-induced one-pot syntheses of 2-methylbenzofurans from norbornyl derivatives have been reported. The construction of new C–O bond proceeds via Grob-type fragmentation followed by cyclization and aromatization respectively. This synthetic strategy facilitates the efficient synthesis of 2-methylbenzofurans under acidic conditions. Significantly, this methodology is successfully applied to the synthesis of 6,7-bisaryl benzofurans. [ABSTRACT FROM AUTHOR]

• Acid mediated synthesis of thiazolines and enamide derivatives from methyl enol ethers. • Enol ethers acts as an electrophile. • C–N and C–S bond formation was achieved. • Application towards wilsoniamine B alkaloid. An efficient metal-free synthesis of thiazolines, dihydrothiazole and enureas or thioureas from methyl enol ether with urea or thiourea derivatives in the presence of TFA (trifluoroacetic acid) are reported here. This synthetic protocol involves the formation of two bonds, C–N as well as C–S, in one step for the synthesis of thiazoline derivatives, dihydrothiazoles and a direct C–N bond for the synthesis of enamides with good to excellent yields. Further, this method was employed for the synthesis of wilsoniamine B alkaloid. [ABSTRACT FROM AUTHOR]

An efficient synthesis of diarylmethane derivatives from phenol and a p -quinone methide surrogate cyclohexadienone derivative has been described. This 1,6-conjugate addition reaction is catalyzed by earth abundant FeCl 3 and it proceeds via a consecutive Michael type addition followed by aromatization. Various proportions of phenol and cyclohexadienone produced exclusively mono, bis and tris addition products. Interestingly, di- tert -butylphenol gave addition product with concomitant loss of one of the tertiary butyl groups of the phenol moiety via retro-Friedel-Crafts reaction. This strategy demonstrates a straightforward access to wide range of diarylmethane derivatives possessing biologically significant ortho -methoxyphenol moiety under mild reaction conditions. Image 1 • FeCl 3 Catalyzed synthesis of diarylmethane derivatives from phenol and cyclohexadienone derivative. • In this strategy mono, bis and tris 1,6-conjugate addition products are achieved successfully. • Here we disclosed a novel approach for biologically significant diarylmethane derivatives under mild reaction conditions. • An interesting plausible mechanism has been discussed for diarylmethane derivatives. [ABSTRACT FROM AUTHOR]

Abstract: A concise stereoselective route to (±)-pentenomycin 1 in 33% overall yield starting from the readily accessible Diels–Alder adduct 4 is reported. The key reaction involves decarbonylation of β-methoxy-α,β-unsaturated aldehyde 8 obtained from β-hydroxy-dimethylketal 6. [Copyright &y& Elsevier]

• Total synthesis of (±) aspidostomide B, C and regioisomeric N -methyl aspidostomide is reported. • An unusual Lewis acid-mediated regioselective epoxide opening is described. • Aspidostomide B, C was achieved in six steps with overall yields of 54.7 and 59.0% respectively. A full account of the total synthesis of aspidostomide B, C, their analogues and our synthetic efforts towards the synthesis of aspidostomide D, which led to the synthesis of regioisomeric N -methyl aspidostomide D, its analogues via epoxide opening strategy is presented. The synthesis of regioisomeric N -methyl aspidostomide D involves an efficient, five-step sequence, with 36.3% overall yield, starting from 3,4,5-tribromo-1H-pyrrole-2-carboxylic acid. The key features of this protocol are intramolecular cyclization, dehydration, oxidation, and a Lewis acid-mediated regioselective epoxide ring opening by C-3 position of 2,5-dibromo-1H-indole to furnish the title compounds. [ABSTRACT FROM AUTHOR]

A general and catalyst-free protocol for the synthesis of pyrido-oxazepine-3-ols and benzo-oxazin-2-yl methanol via tandem epoxide opening followed by S N Ar reactions is reported. Oxirane derived from tribromopyridine undergoes epoxide opening followed by the S N Ar reaction, yielding seven-membered pyrido-oxazepine-3-ols. Predominantly 2-cyclized pyrido-oxazepine-3-ols observed in this reaction. Oxirane derived from tribromonitrobenzene undergoes epoxide opening followed by S N Ar reaction to produce six-membered benzo-oxazin-2-yl methanol. When oxirane treated with primary amine, mainly 2-cyclized benzo-oxazin-2-yl methanol is formed. furthermore, treatment of oxirane with secondary amine result in regio-selective 4-cyclized benzo-oxazin-2-yl methanol, accompanied by de-alkylation. A plausible reaction mechanism is proposed for the synthesis of benzo-oxazin-2-yl methanol, which proceeds via epoxide opening followed by a Smiles rearrangement. [Display omitted] [ABSTRACT FROM AUTHOR]

Synthesis of brominated marine natural product amathamide F is described. Various strategies to construct the enamide functionality required for its synthesis have been explored. Finally, we succeeded in constructing the enamide moiety under a palladium-catalyzed condition. Facile transformation of 2,3,4-tribromo-5-methoxybenzaldehyde to the reported structure of amathamide F involved initial one-carbon-elongation of the aldehyde group followed by its conversion to corresponding enol acetate derivative prior to crucial Pd(II)-catalyzed cross-coupling with ( S )-1-methylpyrrolidine-2-carboxamide. However, due to nonconformity of its NMR spectral data to that of the reported natural isolate, we have confirmed its actual structure through a synthesis. [ABSTRACT FROM AUTHOR]

Curcumin, a popular herbal medicine derived from turmeric, blocks the synthesis of prostaglandins by inhibiting Cyclooxygenase-1 and 2 (COX-1 and COX2). We have recently reported an efficient method of synthesizing curcumin and synthesised analogues. In the present study, we have investigated sixteen novel analogues of curcumin for their ability to inhibit COX-1 and COX-2. We report here that most of the curcumin analogues display selective inhibition of COX-2, whereas a few suppress COX-1 activity. Further, we examined the binding of these inhibitors by molecular docking and observed that the compound with pronounced selectivity for COX-2 displayed better binding to COX-2 compared to curcumin. [Display omitted] [ABSTRACT FROM AUTHOR]

The mammalian AlkB homologue-3 (AlkBH3) is a member of the dioxygenase family of enzymes that in humans is involved in DNA dealkylation repair. Because of its role in promoting tumor cell proliferation and metastasis of cancer, extensive efforts are being directed in developing selective inhibitors for AlkBH3. Here we report synthesis, screening and evaluation of panel of arylated indenone derivatives as new class of inhibitors of AlkBH3 DNA repair activity. An efficient synthesis of 2,3-diaryl indenones from 2,3-dibromo indenones was achieved via Suzuki-Miyaura cross-coupling. Using a robust quantitative assay, we have obtained an AlkBH3 inhibitor that display specific binding and competitive mode of inhibition against DNA substrate. Finally, we established that this compound could prevent the proliferation of lung cancer cell line and enhance sensitivity to DNA damaging alkylating agent. [ABSTRACT FROM AUTHOR]

A regioselective synthesis of carbazole analogs belonging to both the categories of natural origin, viz., microorganisms and higher plant source is reported. The synthesis of carbazole derivatives possessing a methylester group at C-1 position has been achieved by Cadogan cyclization of nitro bi-phenyl derivatives, whereas, the carbazole analog possessing a methylester group at C-3 position was synthesized by Buchwald–Hartwig Pd-catalyzed cyclization of amino bi-phenyl derivatives. Suitably substituted bi-phenyl precursors were accessed from norbornyl α-diketones via Grob fragmentation, O-methylation and DBU aromatization reaction sequence. The reported carbazole derivatives possess structural features that are common with many carbazole natural products: mukonine, clausine-L, murrayafoline-A, and their sibling natural products. [ABSTRACT FROM AUTHOR]

A short and generally applicable synthesis of bioactive tetracyclic natural product paracaseolide A has been accomplished employing a ‘proposed’ biomimetic Diels–Alder reaction as the key strategic step. The Diels–Alder precursors for this purpose were readily assembled through a versatile Suzuki coupling on preformed α-halo butenolides. The mechanistic aspects of the ‘putative’ biomimetic Diels–Alder reaction have been probed using computational methods, which suggest that this [4+2]-cycloaddition proceeds through a step-wise process and product profile is thermodynamically governed. [ABSTRACT FROM AUTHOR]

[Display omitted] Marine sponges of the genus Suberea produce variety of brominated tyrosine alkaloids which display diverse range of biological activities including antiproliferative, antimicrobial and antimalarial activities. In continuation of our search for biologically active marine natural products for antibacterial compounds, we report here the synthesis and evaluation of biological activity of panel of ianthelliformisamines and subereamine analogues using the literature known acid-amine coupling reaction. Several derivatives of Ianthelliformisamine were achieved by the coupling of Boc-protected polyamine chain with brominated aromatic acrylic acid derivatives by varying the bromine substituents on aromatic acid derivatives, amine spacer as well as geometry of the double bond, and then Boc-deprotection using TFA. Similarly, subereamine analogues were also synthesized employing coupling reaction between various brominated phenyl acrylic acids with commercially available chiral amino ester derivatives followed by ester hydrolysis. We screened these synthetic analogues for antibacterial activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) strains. One of the compound 7c showed bactericidal activity against Staphylococcus aureus with an IC 50 value of 3.8 μM (MIC = 25 μM). [ABSTRACT FROM AUTHOR]