One-pot synthesis of phthalides via regioselective intramolecular cyclization from ortho-alkynylbenzaldehydes

A one-pot synthesis of phthalides via an intramolecular 5-exo-dig cyclization of ortho-alkynylbenzaldehydes under mild NaClO₂ oxidation conditions is described.     

A facile one-pot protocol for the synthesis of tetrazolyl-tetrahydroisoquinolines via novel domino intramolecular cyclization/Ugi-azide sequence

A facile one-pot, four-component domino reaction between 2-(2-bromoethyl)benzaldehyde, isocyanide, amine, and azide for the synthesis of tetrazolyl-tetrahydroisoquinoline derivatives has been developed. The reaction sequence involves intramolecular replacement of halide by iminium nitrogen followed by Ugi-azide reaction. The reaction is catalyst/additive free and takes place under ambient conditions with short reaction times to furnish products in good to excellent yields.     

Temperature-controlled divergent synthesis of 4-alkoxy- or 4-alkenyl-chromanes via inverse electron-demand cycloaddition with in situ generated ortho-quinone methides

The temperature-controlled divergent synthesis of 4-alkoxy- or 4-alkenyl-chromanes via inverse electron-demand cycloaddition with in situ generated ortho-quinone methides under identical reaction conditions except for thermal condition has been developed. At room temperature, the reaction generated 4-methoxychromanes, whereas the reaction performed at room temperature to 100?°C gave 4-alkenylchromanes. Trifluoromethanesulfonic acid was efficiently suitable in the reaction to give the 4-substituted chromanes. This divergent synthetic strategy exhibits a new method giving carbon–carbon or carbon–oxygen bond by controlling the reaction temperature.     

Microwave-assisted facile synthesis of [a]-annelated pyrazolopyrroloindoles via intramolecular azomethine imine 1,3-dipolar cycloaddition

The synthesis of [a]-annelated pyrazolopyrroloindoles via intramolecular 1,3-dipolar cycloaddition of in situ generated azomethine imine from N-allylated indole-2-carboxaldehyde, in regio- and stereoselective manner by using microwave irradiation is described. A one-pot strategy for the expedient synthesis of pyrazolopyrroloindoles has been developed.     

A facile and convenient synthesis of functionalized ortho-nitrophenylboronic acids

A variety of ortho-nitrophenylboronic acids bearing functional groups such as cyano, nitro, halo, α-bromomethyl, and ester were prepared in good yields via I-Mg exchange followed by quenching with trimethyl borate. All reagents employed in this procedure are commercially available and were used without further purification, and the procedure can be executed in about an hour.     

Stabilization of ortho-quinone methides by a bis(sulfonium ylide) derived from 2,5-dihydroxy-[1,4]benzoquinone

The zwitterionic intermediates (2a) in the oxidation of ortho-alkylphenols (1) and bis(sulfonium ylide) 3 form reasonably stable 2:1-complexes (4), in which the ortho-quinone methide (oQM) moieties are not present in quinoid form with the exocyclic in-plane methylene group, but as zwitterionic, aromatic conformer having an out-of-plane exocyclic methylene group. The complex 7 derived from the α-tocopherol model compound PMC (5) was comprehensively characterized. As exemplarily demonstrated, the adducts can be advantageously employed in organic synthesis as ‘stabilized oQMs’.     

A facile and practical one-pot synthesis of multisubstituted 2-aminothiophenes via imidazole-catalyzed Gewald reaction

A simple and efficient procedure was developed for the synthesis of multisubstituted 2-aminothiophene derivatives. In the presence of catalytic amount of imidazole, ketones or aldehydes, dicyanomethane and elemental sulfur were converted into the corresponding 2-aminothiophene derivatives in moderate to high yields in DMF at 60 °C.     

An efficient one-pot synthesis of C2-symmetric triazolophanes by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction

A facile and efficient one-pot synthesis of 12-15-membered triazolophanes has been accomplished using CuAAC methodology. The formation of triazolophanes was confirmed by spectral analysis and the products were isolated in good yield. The effect of solvents on this reaction was also studied.     

An efficient one-pot synthesis of spiro dihydrofuran oxindole and spiro 2-hydroxytetrahydrofuran oxindole derivatives via (3+2) oxidative cycloaddition mediated by CAN

Spiro dihydrofuran oxindole derivatives were prepared via a (3+2) oxidative cycloaddition of 1,3-dicarbonyl compounds to 3-(phenyl-2-oxoethylidene)-1-methyloxindole and 3-benzylidene-1-methyloxindole derivatives mediated by ceric ammonium nitrate. In the case of the reaction of 3-(phenyl-2-oxoethylidene)-1-methyloxindole derivatives with acyclic 1,3-dicarbonyl compounds, spiro 2-hydroxytetrahydrofuran oxindole derivatives were obtained.     

A facile, mild and efficient one-pot synthesis of 2-substituted indole derivatives catalyzed by Pd(PPh3)2Cl2

2-Phenylindoles were prepared by heteroannulation of 2-haloaniline derivatives and phenylacetylene under mild conditions in a one-pot reaction catalyzed by Pd(PPh3)2Cl2.     

Copper-catalyzed one-pot synthesis of 2-thioxo-2,3-dihydroquinazolin-4(1H)-ones from ortho-bromobenzamides and isothiocyanates

Copper-catalyzed tandem reaction of ortho-bromobenzamides and isothiocyanates is described, which provides an efficient and practical route for the synthesis of 2-thioxo-2,3-dihydroquinazolin-4(1H)-ones. The optimal condition involved the following parameters: CuI as precatalyst, Cs₂CO₃ as base, N,N′-dimethylethane-1,2-diamine as ligand, and toluene as solvent, with reaction temperature at 120 °C.     

A convenient one-pot synthesis of o-phenylene bis(diphenylphosphine)

The reaction between $\text{o}$-difluorobenzene and sodium diphenylphosphide in liquid ammonia provides a convenient synthesis of the title compound.     

Catalyst-free synthesis of 2,3-dihydrobenzofurans through [4+1] cycloaddition of ortho-hydroxyphenylsubstituted para-quinone methides and sulfur ylides

An efficient [4+1] cycloaddition of ortho-hydroxyphenylsubstituted para-quinone methides and sulfur ylides was achieved under the catalyst-free condition. With this developed protocol, a series of trans-2,3-dihydrobenzofurans were obtained in excellent yields (up to 99%) with high diastereoselectivities (>20:1 dr). The usefulness of the protocol was also demonstrated by the versatile conversions of the 2,3-dihydrobenzofurans into other functionalized benzofurans.     

An efficient and facile one-pot synthesis of cyanohydrin esters from carbonyl compounds catalyzed by iron(III) chloride

A variety of cyanohydrin esters were readily prepared from carbonyl compounds with trimethylsilyl cyanide and acid anhydride under the influence of a catalytic amount of iron(III) chloride in a convenient one-pot procedure.     

Logical design and synthesis of indole-2,3-diones and 2-hydroxy-3(2H)-benzofuranones via one-pot intramolecular cyclization

A novel and attractive protocol to synthesis indole-2,3-diones and 2-hydroxy-3(2H)-benzofuranones and via copper(II) oxide catalyzed intramolecular cyclization is described. This method possesses functional-group compatibility, easy workup procedure, shorter reaction time and high yields.     

A mild and efficient one-pot synthesis of 2-dihydroimidazoles from aldehydes

The reactions of various aldehydes and 1,2-diamines followed by NXS treatment proceed at 0 °C-rt to give the corresponding dihydroimidazoles in high yields. The reaction is mild, and many functional groups such as halogens, nitriles, and esters can exist.     

A highly efficient total synthesis of (R)-(+)-muscopyridine by intramolecular [4+2] cycloaddition of bisketene

A highly efficient total synthesis of (R)-(+)-muscopyridine 1 has been accomplished in 12 steps with 40% overall yield. A highlight of the synthesis is the intramolecular [4+2] cycloaddition of bisketene to afford a bridged pyrone and ring transformation of the pyrone to afford pyridine derivatives.     

Reductive heterocyclizations via indium/iodine-promoted one-pot conversion of 2-nitroaryl aldehydes, ketones, and imines

2-Nitroaryl aldehydes, ketones, and imines were reductively cyclized to 2,1-benzisoxazoles with good yields in the presence of indium and iodine in MeOH. Under a similar condition, N-(2-nitrobenzylidene)anilines were produced mixtures of 2,1-benzisoxazoles and 3-anilino-2-phenyl-2H-indazoles.     

Efficient catalyst-free synthesis of diversified bis (spirooxindoles) via one-pot,three-component reaction

A catalyst-free, one-pot synthesis of bis-spirooxindoles has been carried out by a three-component reaction of bis-isatins, malononitrile, and various cyclic enolizable carbonyl compounds in ethylene glycol at 100?°C. The protocol provides an easy and simple route for the synthesis of such complex compounds, in short reaction times and high yields. No chromatographic techniques have been employed for the purification of the compounds.