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Recently, the structural information about non-coking and coking coal has attracted pronounced interest for sustainable utilization of poor coking coal in different industries specifically for stee...

A general synthesis of 3,4-dihydro-1H-furo[b]indol-1-ones, representing a furanone-fused pyrrole unit, has been developed. The dehydrohalogenative cyclization of 4-aminofuranones was achieved by reaction with Pd(OAc)2 and DABCO in DMF. The corresponding N-protected indolones undergo alkylation at C3.

This study discloses an efficient synthetic route for the regiospecific construction of a C5 glycoside angucycline representative of mayamycin. The key steps are intramolecular aldol condensation and Hauser annulation, and the key precursor for the aldol reaction is accessible through utilization of α-lithiation of a vinyl ether.

In this work, brominated hydroxyanthraquinones, which are the core structural motif of naturally occurring bromorhodocomatulins, were successfully synthesized using Hauser annulation reaction as the key step. When brominated Michael acceptors (brominated p-quinone monoketals) and cyanophthalides or bromocyanophthalides (Hauser donors) were reacted under the annulation conditions, brominated anthraquinones were obtained with 81–87% yields for four examples. On acidic quenching, products were obtained as solid which were separated by filtration and purified by recrystallization in acetone. No chromatography was required.

Several glycosyl donors have been systematically investigated for C-glycosylation of substituted β-naphthols to delineate the effect of the substituents. Whereas glycosylations of the parent 2-naphthol are smoothly achievable, those of differently substituted 2-naphthols are cumbersome. Efficiency of the glycosylation depends on the nature of both the glycosyl donors and the substituents of the arene ring. Among various glycosyl donors, trichloroacetimidate glycosyl donors are found to be superior for glycosylation with substituted 2-naphthols.

K-259-2, a unique calmodulin antagonist, is an allyl chain containing anthraquinone natural product. A regiospecific synthetic approach towards K-259-2 is herein represented. The study also showcases a protocol for synthesizing heavily substituted bromo naphthoate which was found to be suitable for fabricating the K-259-2 motif.

Hexa-2,5-dienoates, susceptible to isomerization by acids and bases, are suitable for the [4+2] anionic annulation to give 3-(2-alkenyl)naphthoates in regiospecific manner. When combined with intramolecular carbonyl-ene reaction (ICE), the accessibility of the naphthoates culminates in a new synthesis of anthraquinones and diastereoselective synthesis of tetrahydroanthraquinones. This strategy has also resulted in a 3-step synthesis of dehydroherbarin from a 3-methallylnaphthoate.

Mercury ion is of great threat to the human kind due to its high toxicity in live systems. Consequently, its detection at nanolevel is of current interest. The rhodamine derivative is one of the rarest examples of fluorescent chemosensors for Hg2+, wherein a phthalaldehydic acid moiety which shows antibacterial activity, is responsible for specific binding. By using fluorescence correlation spectroscopic (FCS) study of the probe, it has been possible to detect Hg2+ in solution at a level as low as ∼5 pM. This sensing, applicable to fluorescence lifetime imaging of live cells, provides a novel microscopic technique.

2-Methallyl aromatic aldehydes, synthesized by Suzuki coupling of 2-formylphenylboronic acids, are shown to provide cycloalkylidene ene products under acidic conditions. Susceptibility of the products to aromatization is manoeuvred by varying the reaction conditions and catalysts including binol-derived Bronsted acid catalysts. A peri-effect is identified as a controlling factor for the aromatizations. Several oxidative transformations of an ene product are carried out as model studies of hydroaromatic polyketide natural products.

The reaction of 3-nucleofugal phthalides with 2-amidoacrylates is shown to provide a synthesis of densely substituted naphth[2,1-d]oxazoles in good yields. It is proposed to proceed via a five-step cascade which includes phthalide annulation, demethoxycarbonylation, and heterocyclization. The methodology is free from regiochemical ambiguity of the products. In certain cases, the corresponding 2-amidonaphthoquinones are directly formed.

It may appear that 1,4-dipolar donor, an acceptor with a polarized CC multiple bond and an alkali metal strong base would suffice to execute a successful Hauser-type annulation. However, reasonable understanding of the reaction and the possible competing reactions is warranted for the success. There are examples which prove to be the exceptions of the generalized reaction. For examples, the Tamura annulations with unsaturated ketones are not often successful. It is precluded with simple Michael acceptors such as methyl acrylate and acrylonitrile. There are more than six possible ways by which an expected [4 + 2] anionic annulation may be foiled. This chapter exclusively deals with accessibility of the starting 1,4-dipolar reagents and choice of reaction conditions. In the later part, the factors that influence the successes and setbacks of the anionic annulation chemistry are highlighted.

Hauser annulation was discovered in 1978 and over the years it has had an enormous impact on organic synthesis. In this chapter, Hauser annulation is defined. A historical perspective of the anionic annulation in general is presented.

The reaction of 3-cyanophthalides with allene carboxylates in the presence of tBuOLi results in a tandem annulation furnishing naphtho[b]furanones in good yields with no loss of carbon. The carbon economy is explained by a tandem process, in which the initially expelled cyanide induces the second annulation.

Anionic annulations of 3-nucleofugal phthalides with α-alkyl(aryl)acrylates involving a demethoxycarbonylation provide a succinct synthesis of vitamin K and related naphthoquinones. Also reported is a new cascade reaction stemming from a Cope-retro-Wittig rearrangement. This cascade leads to direct formation of 1-hydroxy-4-prenyloxynaphthalene-2-carboxylates from the corresponding α-prenyl acrylate acceptors.

N-Boc/MOM-protected furoindolones, synthesized in four steps, have been successfully employed in the Hauser annulations with Michael acceptors to provide a new synthesis of carbazole-1,4-quinones. This methodology works well with a number of acceptors, and constitutes an efficient route for the synthesis of benzo[b]carbazoloquinones. The nature of N-protection of the synthons plays a crucial role in the success of annulations.

An efficient process for the Cu(I)-mediated methylthiolation of haloarenes using simple and readily available DMSO as a convenient and environment friendly source of SMe moiety has been developed. In the presence of CuI and DABCO, a variety of aryl/heteroaryl halides reacted with DMSO to afford corresponding aryl methyl sulfides in good to excellent yields.

C-Glycosylations of several 2-naphthols with different glycosyl donors have been investigated in the pursuit of the total synthesis of mayamycin ( 1 ). While glycosylations of the parent 2-naphthol are readily achievable, those of 5-methoxy-7-methyl-2-naphthol ( 6 ) embodying the target are ineffective under different Lewis acidic conditions. The inefficiency of the glycosylation of 6 has been attributed to the steric effect exerted by C7 methyl group, which was corroborated by glycosylation studies of different 2-naphthols.

3-Isocyanoisobenzofuran-1(3H)-ones (phthalides) were prepared in two steps from the corresponding phthalaldehydic acids. The 3-isocyanoisobenzofuran-1(3H)-ones are readily rearranged to the corresponding 3-cyanoisobenzofuran-1(3H)-ones using triflic anhydride and 2,6-lutidine, thus enabling the synthesis of 3-cyanoisobenzofuran-1(3H)-ones without using toxic cyanide. Furthermore their annulation with Michael acceptors results in direct formation of 1,4-naphthoquinols/1,4-naphthoquinones in moderate yields.

4-Bromo-1-methoxycarbazole-3-carboxylate has been synthesized by a sequence of benzannulation–decarboxylation–bromination, and utilized as a common intermediate for the first total synthesis of clausamine E and the second synthesis of furanoclausamine B. Heck coupling and Br–Li exchange reactions are, respectively, employed as the key steps.

Trimethylsilyl cyanide (TMSCN) in the presence of PhI(OAc)2 and BF3.OEt2 in dichloromethane is shown to be effective for direct conversion of phthalaldehydic acids into 3-cyanophthalides at rt in good–excellent yields. A number of substituents in the substrates tolerate the reaction conditions. This method works well also with 2-formylbenzamides.

The preparation of several functionalized furan derivatives and attempts to transform them into a derivative containing 6H-furo[3,4-b]furanone skeleton towards the construction of naphtho[2,3-b] furan are described. Attempted Pummerer reaction of a furan sulfoxide derivative produced four interesting furan derivatives. Base promoted annulation between methyl 2-(phenylsulfinylmethyl)-3-furoate and 2-cyclohexenone proceeded to give dihydro naphtho[2,3-b]furanone derivative in a regiospecific manner.

The anionic annulation of MOM-protected furoindolone with 4-bromoquinoline followed by deprotection of the N-MOM group provides calothrixin B, whereas that with 3-bromoquinoline yields isocalothrixin B. The outcomes are explained by the divergence of the reaction mechanism from commonly perceived quinolyne intermediate. A sequence of addition-cyclization-elimination is proposed to account for the formation of calothrixin from 4-bromoquinoline.

Anionic annulation of appropriate 2,3-disubstituted pyrroles with Michael acceptors provides an expedient route to densely substituted 7-hydroxyindoles. Intrinsic to the methodology, the resulting substituents are disposed in a fully regiocontrolled manner. The methodology is applicable to the synthesis of 7-hydroxybenzofurans. None of the indoles/benzofurans or pyrrole synthons synthesized in this study have hitherto been reported.

The anionic [4 + 2] annulation of 3-substituted furoindolones with dimethyl maleate provides an expedient route for the synthesis of the title carbazole alkaloids. The employment of this strategy in combination with a Krapcho reaction/retro-Kolbe–Schmitt reaction has culminated in the first total synthesis of the lactonic carbazoles harmandianamine A and furanoclausamine B and a brief total synthesis of ekeberginine from a prenylated furoindolone. An unusual fragmentation of an ester function during the annulation is also reported.

The cascade annulation-lactonization of phthalides with α-carboxyfurylacrylates in the presence of lithium hexamethyldisilazide (LiHMDS) provides both convergent and semiconvergent regioselective syntheses of neo-tanshinlactones in moderate yields. This methodology also offers an avenue for the direct syntheses of hitherto unreported 6-alkoxycarbonyl-substituted neo-tanshinlactones and their heterocyclic analogues. A new synthesis of 4-alkyl phthalides was developed on the basis of a combination of a Duff reaction and Furstner cross-coupling.

This investigation reports the preparation and self-assembly behavior of polyhedral oligomeric silsesquioxane (POSS) containing poly(caprolactone)-graft-poly(acrylic acid) (POSS-PCL-graft-PAA) polymer. This article focuses on the self-assembly behavior of POSS tethered amphiphilic graft copolymer. In this investigation, POSS tethered alkyne functionalized polycaprolactone (PCL) was prepared by strategic ring opening polymerization (ROP) of e-caprolactone and α-propargyl-e-caprolactone using hydroxyl-terminated POSS as an initiator. Azide-terminated poly(tert-butyl acrylate) (P t BA) was grafted onto functional PCL via Cu-catalyzed azide-alkyne “click” (CuAAC) reaction. Finally, hydrolysis of the tert-butyl ester group into acid furnished the POSS tethered PCL-graft-PAA polymer. This amphiphilic graft copolymer was characterized by GPC, NMR, and FT-IR analyses and the morphology of the graft copolymer analyzed by HRTEM and FESEM analyses. On changing the graft copolymer concentration (low to high) in water, the morphology of the final graft copolymer changed from micelles to worm-like and core-shell. The structural motif of POSS plays an important role in this morphological transformation. The pH sensitivity was studied using DLS analysis as well as via release profile of rhodamine B as a model compound.

Allene carboxylates, scarcely used as Michael acceptors, serve as acceptors in the annulation with phthalides in the presence of LDA and provide a one-pot synthesis of naphtho[c]furanones in very good yields. This tandem annulation is proposed to proceed via transposition of the hydroxy group resulting from the initial annulation.

An efficient and regioselective synthetic route to naphthoquinone/naphthoquinol–carbohydrate hybrids has been developed. It is based upon anionic annulation of 3-nucleofugalphthalides with an acrylate appended sugar moiety. In each of the annulations studied, the arene–carbohydrate hybrids were obtained in good to excellent yields. The in vitro cytotoxic activity of the synthetic naphthoquinone/naphthonol–carbohydrate hybrids were evaluated against the human cervical cancer cell line (HeLa), and a few of them were found to exhibit potent anticancer activity against the cell line.

2-Methallyl aromatic aldehydes, synthesized by Suzuki coupling of 2-formylphenylboronic acids, are shown to provide cycloalkylidene ene products under acidic conditions. Susceptibility of the products to aromatization is manoeuvred by varying the reaction conditions and catalysts including binol-derived Bronsted acid catalysts. A peri-effect is identified as a controlling factor for the aromatizations. Several oxidative transformations of an ene product are carried out as model studies of hydroaromatic polyketide natural products.

Dibromobenzoisofuranone 12, synthesized in six steps, was regiospecifically annulated with 5-substituted cyclohexenones 13/36 in the presence of LiOt-Bu to give brominated anthraquinones 14/38 in good yields. Darzens condensation of 30 was shown to give chain-elongated anthraquinone 32. Alkaline hydrolysis of 38 furnished 39 representing desulfoproisocrinin F.

The new cascade title reaction between 3-cyano phthalides and α-substituted acrylates is elaborated.

A facile protocol for annulation reactions of furoindolones with Michael acceptors or aryne precursors is presented.

The first total synthesis of chlorocyclinone A (1) is regioselectively completed in 28 steps. The key steps are Pd-catalyzed methoxycarbonylation, unprecedented Hauser annulation, Krohn photo-oxidation, and regioselective gem-dichlorination.

The carbazole nucleus is a predominant feature of a vast array of heterocyclic compounds. It occurs in naturally occurring alkaloids, optoelectronic materials, and anion-binding ligands. Due to their various applications, there have appeared a plethora of synthetic methods for the construction of carbazoles. In this update, we focus on the recent developments and studies related to the synthesis of carbazoles spanning the period 2008–2011. Particular emphasis is placed on the methods involving cycloadditions and transition metal-assisted intramolecular aminations.

Anionic [4+2] annulation of lithiated furoindolones with dimethyl maleate followed by selective demethoxycarbonylation provides an efficient synthetic route to 3-methoxycarbonylcarbazoles. The route has led to the straightforward synthesis of two natural products, namely clausine E, mukonine, and their 4-prenyl analogues. A new route to cyclohepta[d,e,f]carbazole was also uncovered during the investigations.