Facile one-pot preparation of 5-aryltetrazoles and 3-arylisoxazoles from aryl bromides

The successive treatment of aryl bromides with n-BuLi, DMF, hydroxylamine hydrochloride, and finally diphenylphosphoryl azide provided efficiently the corresponding 5-aryltetrazoles in good to moderate yields. Similarly, the successive treatment of aryl bromides with n-BuLi, DMF, hydroxylamine hydrochloride, and finally diethyl acetylenedicarboxylate and Oxone^® provided efficiently the corresponding diethyl 3-arylisoxazole-4,5-dicarboxylates in good to moderate yields. Aromatic aldoximes are the key intermediates in both reactions, and 5-aryltetrazoles and 3-arylisoxazoles could be obtained from aryl bromides in one pot under transition-metal-free conditions.     

Microwave-assisted selenium dioxide oxidation of aryl methyl ketones to aryl glyoxals

We report an improved procedure for the synthesis of phenyl glyoxal and a series of para-substituted aryl glyoxals by microwave-assisted selenium dioxide oxidation. The reaction time has been reduced from several hours to three minutes for activated aryl methyl ketone substrates and 18 min for deactivated substrates, with all reactions affording quantitative conversion into the corresponding aryl glyoxals.     

Facile construction of pyrrolophenanthridone skeleton via a one-pot intramolecular Heck reaction and oxidation

Construction of pyrrolophenanthridone skeleton via a one-pot Pd-catalyzed intramolecular Heck reaction followed by oxidation has been achieved in moderate to good yields. The reaction mechanism has been proposed.     

Synthesis of benzocycloalkene derivatives via Pd-catalyzed one-pot two-step reactions of benzocyclic ketones,tosylhydrazide with aryl bromides

A new method for the synthesis of benzocycloalkene derivatives is described, through the palladium-catalyzed one-pot two-step reactions of benzocyclic ketones, tosylhydrazide with aryl bromides. Palladium-carbene complex as an important intermediate undergoes migratory insertion to form benzylpalladium complex, followed by a fast β-hydride elimination to give substituted benzocycloalkenes. The advantages of this reaction include readily available starting materials, broad substrate scope, high efficiency, and gram scale synthesis.     

Solid-phase synthesis of phenols and pyridinones via arylboronation/oxidation protocol using aryl bromides

A sequence of two known reactions, palladium catalyzed arylboronation of arybromide and subsequent oxidation of arylboronate with oxone, has been carried out to prepare functionalized phenols and pyridin-2(1H)-one which were later loaded on to resin for solid-phase synthesis. Using these resin-bound templates, a number of solid-phase methods were developed to generate libraries of substituted phenols and pyridin-2(1H)-one.     

Visible light photoredox catalysis: aerobic oxidation of perimidines to perimidinones

Aerobic oxidation of a series of 2,3-dihydro-1H-perimidines to the corresponding 4- and 6-perimidinones via visible light photoredox catalysis using Ru(bpy)₃²⁺ as a catalyst was reported. The scope and limitation of this oxidation were investigated and a possible photochemical mechanism was proposed.     

Visible light triggered regioselective ring expansion of N-tosylaziridines: An efficient approach to 2-nitroazetidines

Visible light induced ring expansion of N-tosylaziridines with 1-bromo-1-nitroalkanes to afford 2-nitroazetdines in moderate to excellent yields with high regio- and diastereoselectivity is reported. The salient features of the protocol include the first synthesis of 2-nitroazetidines, operational simplicity, utilization of clean, inexpensive and sustainable resources like visible light and atmospheric oxygen under photoredox catalysis at room temperature in one-pot procedure.     

Visible light and base promoted O-H insertion/cyclization of para-quinone methides with aryl diazoacetates: An approach to 2,3-dihydrobenzofuran derivatives

A visible light and base promoted O-H insertion/cyclization of para-quinone methides with aryl diazoacetates is developed. This one-pot two step reaction offers a mild and efficient approach for the synthesis of biologically important 2,3-dihydrobenzofuran derivatives in good yields and moderate diastereoselectivities.     

Base-mediated reaction of vinyl bromides with aryl azides: one-pot synthesis of 1,5-disubstituted 1,2,3-triazoles

A one-pot base-mediated reaction of azides and β- or α-vinyl bromides has been reported. The effects of bases and solvents have been investigated in the process. A variety of 1,5-disubstituted triazoles were prepared in low to good yields. Further studies reveal that the corresponding alkynes were produced as intermediates via elimination reaction. Under the same reaction conditions, the reactions of alkyl alkynes with phenyl azide would give 1,5-disubstituted 1,2,3-triazoles.     

A facile one-pot synthesis of α-fluoro-α,β-unsaturated esters from alkoxycarbonylmethyltriphenylphosphonium bromides

A convenient one-pot synthesis of α-fluoro-α,β-unsaturated esters from ethoxy- and tert-butoxycarbonylmethyltriphenylphosphonium bromide was developed. The fluorinated phosphoranes, generated in situ from alkoxycarbonylmethyltriphenylphosphonium bromides and 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor^®), undergo a Wittig reaction with aldehydes to yield α-fluoro-α,β-unsaturated esters with (Z)-selectivity.     

Conjugated polymers as photoredox catalysts: a new catalytic system using visible light to promote aryl aldehyde pinacol couplings

The conjugated polymer poly-(p)-phenylene (PPP) was synthesized and used as a photoredox catalyst to promote pinacol coupling of aryl-aldehydes with visible light. The reaction required the use of a sacrificial electron donor (Et₃N), and was accelerated by the addition of Lewis and Brønsted acids. A distinct advantage of this photocatalytic system is the robust nature of the system, which is not overly sensitive to impurities, oxygen, or temperature, and proceeds cleanly with few side reactions. As a comparison with the PPP system, the reactivity of Ru(bpy)₃Cl₂, a popular photoredox catalyst was compared. The PPP system was superior to the Ru(bpy)₃Cl₂ for the pinacol couplings in both rate and yield.     

Substitution of both chloro and sulfinyl groups of aryl 1-chlorocyclopropyl sulfoxides in one-pot via cyclopropylmagnesium carbenoids: a synthesis of multi-substituted cyclopropanes

The rearrangement of cyclopropylmagnesium carbenoids, which were generated from aryl 1-chlorocyclopropyl sulfoxides with a Grignard reagent, to allenes was found to be suppressed by adding HMPA as an additive. Alkylation of the cyclopropylmagnesium carbenoids with the Grignard reagent gives mainly alkylated cyclopropylmagnesium chloride instead. The cyclopropylmagnesium chloride intermediate can be trapped with several electrophiles to afford multi-substituted cyclopropanes. This procedure provides a new method for a synthesis of multi-substituted cyclopropanes.     

Addition of aryl cuprates to azides: a novel approach for the synthesis of unsymmetrical diaryl amines

Aryl and benzyl azides react smoothly with aryl cuprates, generated in situ from aryl magnesium bromide and CuCN in THF to furnish a variety of unsymmetrical diaryl amines in good yields. This is the first report on the synthesis of diarylamines from aryl azides and aryl bromides via an organometallic approach.     

A simpler and greener protocol for the preparation of β-acetylamino ketones by a one-pot reaction of aryl aldehydes, enolisable ketones, acetyl chloride and acetonitrile in the presence of zeolite Hβ as a reusable catalyst

β-Acetylamino ketones have been obtained in a one-pot coupling of an aldehyde with an enolisable ketone, acetyl chloride and acetonitrile in the presence of zeolite Hβ as catalyst at room temperature (26-28 °C). The procedure has the advantages of mild workup, circumvention of high temperature and inert atmosphere. The catalyst was found to be recyclable.     

Convergent approach to the maduropeptin chromophore: aryl ether formation of (R)-3-aryl-3-hydroxypropanamide and cyclization of macrolactam

Efficient enantioselective syntheses of the functionalized phenol and diethynylcyclopentene moiety of the maduropeptin chromophore were achieved. Their CsF-mediated coupling yielded a sterically congested aryl propargyl ether. The subsequent intramolecular Sonogashira coupling reaction between the vinyl iodide and diethynyl groups occurred at the appropriate position to yield a macrolactam, which was accompanied by Pd-mediated enyne-yne benzannulation.     

An efficient access to 3,6-disubstituted 1H-pyrazolo[3,4-b]pyridines via a one-pot double SNAr reaction and pyrazole formation

A general and efficient synthetic method for the synthesis of biologically important series of 3,6-disubstituted-1H-pyrazolo[3,4-b]pyridines was discovered. 2,6-Difluoropyridine was deprotonated using 1.1 equiv of n-BuLi in THF at <−60 °C, followed by quenching with a variety of Weinreb amides to generate 2,6-Difluoro-3-ketopyridines in high yields. A mild tandem reaction sequence of selective nucleophilic substitution of the 6-fluoride with a variety of nucleophiles, followed by hydrazine substitution of the 2-fluoride and pyrazole formation in a one-pot fashion afforded a series of 3,6-disubstituted-1H-pyrazolo[3,4-b]pyridines in moderate to good yields.     

Multifunctional catalysis of a ruthenium-grafted hydrotalcite: one-pot synthesis of quinolines from 2-aminobenzyl alcohol and various carbonyl compounds via aerobic oxidation and aldol reaction

The Ru-grafted hydrotalcite was found to be an excellent multifunctional catalyst for one-pot synthesis of quinolines from 2-aminobenzyl alcohol and various carbonyl compounds. These quinolines were obtained through aerobic oxidation by the Ru species, followed by aldol reaction on base sites of the hydrotalcite.     

A new approach to the synthesis of lysophospholipids: preparation of lysophosphatidic acid and lysophosphatidylcholine from p-nitrophenyl glycerate

A new stereospecific synthesis of lysophosphatidic acid and lysophosphatidylcholine is reported. The sequence relies on p-nitrophenyl-d-glycerate as a chiral synthon, including chemoselective reduction of the active ester function without affecting other carboxylic ester groups present in the molecule.     

A new approach to the bicyclo[4.3.0] ring system of natural products from the liverwort: total synthesis of (±)-chiloscyphone and (±)-isochiloscyphone

Construction of the tricyclic derivative 5, a common intermediate for the synthesis of sesquiterpenoids 1-4, was accomplished by using the intramolecular Diels-Alder reaction. Availability of 5 was demonstrated by effective total synthesis of chiloscyphone 1 and isochiloscyphone 2.