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A practical and effective palladium-catalyzed C–H activation/alkene insertion/annulation has been reported for the synthesis of furans and cyclopropanes from cyclic 1,3-diketones or 1,3-indandione and diverse alkenes, resulting in moderate to good yields. This protocol demonstrates excellent selectivity and is well-compatible with a wide range of alkene substrates, exhibiting exceptional regioselectivities, high efficiency, and good functional group tolerance. [ABSTRACT FROM AUTHOR]

An unusual benzofuran synthesis from 2,6-disubstituted phenols and alkynyl sulfoxides is disclosed. Various highly substituted benzofurans were synthesized via the charge-accelerated [3,3]-sigmatropic rearrangement and subsequent substituent migration. Multiaryl-substituted benzofurans and fully substituted benzofurans were prepared on the basis of the unique reaction mechanism. [ABSTRACT FROM AUTHOR]

The effective and mild [4+1] annulation of ninhydrin-derived MBH carbonates with α,β-unsaturated ketones has been developed, providing a wide range of multisubstituted furans in high yields (up to 90%) with excellent β-regioselectivities. In contrast, the polysubstituted cyclopentenes bearing dispiro-bisindanedione motifs were obtained via classical [3+2] annulations by employing ninhydrin-derived MBH carbonates with 2-arylidene-1,3-indandiones under the same catalytic conditions. Furthermore, the structures of two kinds of cycloadducts were straightforwardly confirmed through X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

A TfOH-promoted, metal-free protocol has been unveiled for the synthesis of spiro-furan quinazolinones employing alkynol urea derivatives utilizing alkynyl Prins cyclization reaction. This methodology produces highly functionalized spiro-heterocycles in excellent yields with exclusive E-selectivity under ambient conditions. Furthermore, late-stage modifications incorporate bromide and acetyl functionalities into the synthesized spiro-heterocycles. [ABSTRACT FROM AUTHOR]

The oxidative annulation reaction of ethyl 3-oxo-3-phenylpropanoates with internal alkynes proceeds efficiently in the presence of a Ru(II)-catalyst, a copper oxidant and an additive such as AgSbF6 to give poly-substituted furans, which offers a novel method for the selective construction of poly-substituted furans. The reaction has wider substrate scope with simple starting materials, and the desired tetrasubstituted furans were prepared in good to excellent yields. [ABSTRACT FROM AUTHOR]

Ring-opening of furans at the equatorial methylene bridge positions of a calix[4]arene gives access to a range of new molecules (in good yield) that have widespread potential impact in supramolecular chemistry amongst other areas. [ABSTRACT FROM AUTHOR]

A novel access to fused furan cores using silver oxide(I) has been developed. Mechanistic investigations indicate the involvement of a Conia-ene reaction/radical cyclization for an expedient path to complex furan derivatives. The reaction is broad in scope with interesting atom economy and can also be conducted in a one-pot fashion from readily accessible α,β-unsaturated ketones. [ABSTRACT FROM AUTHOR]

Enynones are powerful synthons for constructing furan derivatives in the presence of transition metal catalysts. Unlike the conventional intramolecular nucleophilic attack with the activation of coinage metals, we propose that enynones undergo an oxidative cyclization process with a Pd(0) species. The full catalytic cycle involves oxidative cyclization, isocyanide insertion, and reductive elimination, which was supported by DFT calculations. Geometric and electronic analyses confirmed the oxidative cyclization process, which proceeds VIA a Pd(II) intermediate. [ABSTRACT FROM AUTHOR]

An efficient synthesis of 2,5-disubstituted furans directly from alkynyl ketones has been developed via tandem gold(I)-catalyzed isomerization of alkynyl ketones to allenyl ketones and cycloisomerization. The key to the success of this chemistry is the use of a biphenyl-2-ylphosphine ligand featuring a critical remote tertiary amino group. [ABSTRACT FROM AUTHOR]

Palladium-catalyzed cascade reactions of enynones and isocyanides have been disclosed. This strategy allows for the synthesis of structurally unusual furan-incorporated ketenimines, which are stable and can undergo a formal [4+1] annulation with another isocyanide to yield indenone derivatives. [ABSTRACT FROM AUTHOR]

A straightforward strategy for synthesis of highly functionalized trifluoromethyl 2H-furans is described. The copper catalyzed method relies on a cascade cyclic reaction between enaminones and N-tosylhydrazones. This method allows the synthesis of 2-amino-3-trifluoromethyl-substituted 2H-furan derivatives carrying a quaternary stereogenic center as single diastereomers. The proposed reaction mechanism involves an amino-cyclopropane intermediate formed in the cyclopropanation of enaminones. The developed method tolerates a broad spectrum of functionalities, and the obtained 2H-furan derivatives are useful synthetic intermediates for preparing other trifluoromethyl-substituted compounds. [ABSTRACT FROM AUTHOR]

A novel rearrangement of ester-activated propargylic acetate with isocyanide has been disclosed. This protocol enables a quick synthesis of polysubstituted furan derivatives. The reaction outcome also reveals that the ester group is employed for the construction of a furan ring and an acyl migration is observed. [ABSTRACT FROM AUTHOR]

The angle strain induced by ring annulation on a spiro-type naphthofuran weakens its C(sp3)–O bond at the opposite peri-position and endows expandability, so that quite different bond lengths [1.493(3)–1.526(6) Å] are determined for the elongated C(sp3)–O bond of the corresponding spiro-acenaphthofuran derivative upon X-ray analyses of its pseudopolymorphs. [ABSTRACT FROM AUTHOR]

Novel stable tellurium-containing carbohydrate derivatives are prepared from hexitols and pentitols through a double nucleophilic substitution with NaHTe in PEG-400. These tellurosugars react at very high rates with two-electron oxidants, including hypochlorous and peroxynitrous acid, formed at sites of inflammation, and show considerable promise as protective agents against oxidative damage. [ABSTRACT FROM AUTHOR]

An efficient synthetic method for 2,3-allenylamides having an oxygen functionality at the 2-position, which are difficult to access by conventional methods, was newly developed by utilizing the [1,2]-phospha-Brook rearrangement under Brønsted base catalysis. Further manipulation of the 2,3-allenylamides via gold-catalyzed cycloisomerization enables the formation of 2-aminofuran derivatives. [ABSTRACT FROM AUTHOR]

All eight possible stereoisomers of 2,3,6-trideoxyhexopyranosides are prepared systematically from furan derivatives by a sequence of Achmatowicz rearrangement, Pd-catalysed glycosidation, and chiral catalyst-controlled tandem reductions. This sequence provides access to all possible stereoisomers of naturally occurring rhodinopyranosides, amicetopyranosides, disaccharide narbosine B, and other unnatural oligomeric 2,3,6-trideoxyhexopyranosides. It comprises a unique and systematic strategy for the de novo synthesis of deoxysugars. [ABSTRACT FROM AUTHOR]

An efficient enantioselective [3+2] cycloaddition of alkynes with oxiranes via selective C-C bond cleavage of epoxides was developed. A number of optically active 2,5-dihydrofurans were obtained in excellent yields (up to 99%) and enantioselectivities (up to 95% ee) under mild reaction conditions. Moreover, chiral tetrahydrofuran could also be obtained by cycloaddition of alkene and oxirane or hydrogenation of chiral 2,5-dihydrofuran. [ABSTRACT FROM AUTHOR]

The difunctionalization of electron-enriched styrenes for the synthesis of substituted tetrahydrofurans and tetrahydropyrans in the presence of photoredox catalysts is described. The procedure is highlighted by its operational simplicity, low catalyst loadings (1 mol%), excellent stereoselectivity and mild reaction conditions. [ABSTRACT FROM AUTHOR]