Highly regioselective synthesis of aryl chalcogenides through C-H functionalization of arenes

We report here the regioselective synthesis of aryl chalcogenides through the iridium-catalyzed meta C-H borylation followed by copper-catalyzed C-S coupling reaction with chalcogenide sources in one pot, giving the 3,5-disubstituted aryl chalcogenides with high regioselectivity and good yields.     

A facile and regioselective synthesis of 2,5-disubstituted pyrroles via gold-catalyzed cycloisomerization of acetylenylaziridines

Gold-catalyzed cycloisomerization reaction of acetylenylaziridines provides 2,5-disubstituted pyrroles in high yields. The presence of protic species accelerates the reaction rate and improves the yields of pyrrole products.     

Highly regioselective synthesis of polysubstituted pyrroles through three-component reaction induced by low-valent titanium reagent

1,2,3,5-Tetrasubstituted and 1,2,3,4,5-pentasubstituted pyrroles may be synthesized through three-component reaction of 1,3-diketones, aldehydes, and amines induced by low-valent titanium reagent. High regioselectivity was achieved. Compared with the classical synthetic method, this new method has the advantages of short reaction time (15 min), high yields, convenient manipulation, and high regioselectivity.     

A regioselective synthesis of poly-substituted aryl triflones through self-promoting three component reaction

In the absence of any additional catalysts, the reactions of (CF(3)SO)(2)CH(2), aldehydes, and 1,3-dienes gave gem-bis(triflyl)cyclohexenes in excellent yields with high regioselectivity. gem-Bis(triflyl)cyclohexene products can be easily converted to the corresponding aryl trifluoromethyl sulfones.     

Highly regioselective radical alkylation of 3-substituted pyrroles

It is reported that the intermolecular oxidative radical substitution on 3-substituted pyrroles gives the 2,3-disubstituted pyrroles in a highly regioselective manner. This behavior is explained on the basis of the relative stabilities of the intermediate radicals formed in the process. The methodology reported herein represents a direct entry into 2,3-disubstituted pyrroles, which might be used to construct more complex molecules.     

Efficient and regioselective synthesis of functionalized pyrroles by cyclocondensation of 1,3-dicarbonyl dianions with alpha-azidoketones

The cyclocondensation of 1,3-dicarbonyl dianions with alpha-azidoketones regioselectively afforded 2-alkylidenepyrrolidines which were transformed into functionalized pyrroles by treatment with acid.     

A regioselective synthesis of aryl substituted arylacetates through ring transformation by ethyl levulinate

A regioselective synthesis of sterically hindered ethyl arylacetates in one step through ring transformation of suitably functionalized 6-aryl-3,4-disubstituted-2H-pyran-2-ones with ethyl levulinate at room temperature in excellent yields is described.     

A substituent directed regioselective synthesis of aryl/pyronyl pendant unusual adipate and tetrahydronaphthalene

An efficient regioselective synthesis of pyronyl pendant ethyl methylthiocarbonylalkanoates 5 has been delineated from the base catalyzed reaction of suitably functionalized 2-pyranone 1 and 2-carbethoxycycloalkanones 2, 6 through successive substitution and regioselective ring opening by in situ generated mercaptide ion. To assess the effect of C-4 substituent on regioselectivity, reactions of 6-aryl-3-cyano-4-(piperidin-1-yl)-2-oxopyran 8 with 2-carbethoxycyclohexanone 6a and 2-carbethoxy-2-methylcyclohexanone 6b were carried out separately under analogous reaction conditions but the compounds isolated were identical and characterized as 4-aryl-8-methyl-2-piperidin-1-yl-5,6,7,8-tetrahydronaphthalene-1-carbonitriles 9. Ethyl 2-(5-amino-4′-bromo-4,6-dicyanobiphenyl-3-yl)-5-methylsulfanylcarbonylpentanoate 10 has also been prepared through base catalyzed ring transformation of ethyl 2-[6-(4-bromophenyl)-3-cyano-2-oxo-2H-pyran-4-yl]-5-methylsulfanylcarbonylpentanoate 5d by malononitrile in DMF.     

The regioselective synthesis of monomethoxynaphthylene diacetates

Methods for the conversion of 1,4,5-naphthalenetriols into the corresponding monomethoxy diacetates are described. All utilise the formation of peri-bridged intermediates.     

New synthesis of pyrroles

The reaction of ammonia or a primary amine with alkyl(cycloaklyl, phenyl)-,-dihalopropyl ketones gives 2-. 2,4-, and 1,2- or 1.2,4-substituted pyrroles in high yields.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 790–793, June, 1976.     

Palladium-catalyzed synthesis of pyrroles

Pyrrole derivatives are prepared in high yields by the catalytic action of a Pd(II) salt on 1-amino-3-alkyn-2-ols which are obtained from conjugate ynones.     

Simple synthesis of substituted pyrroles

Simple synthesis of substituted pyrroles using iodine-catalyzed and montmorillonite KSF-clay-induced modified Paal-Knorr methods has been accomplished with excellent yields. N-Substituted carbazole has also been prepared by following this method. If one of the reactants is a liquid, the reaction proceeds exceedingly well without a solvent. This method gives pyrroles with less nucleophilic multicyclic aromatic amines at room temperature.     

A new synthesis of pyrroles

The radical reaction between an N-ethylsulfonylenamide and an alpha-xanthyl ketone gives an intermediate gamma-keto imine which spontaneously ring-closes to the pyrrole.     

Phosphine-catalyzed regioselective heteroaromatization between activated alkynes and isocyanides leading to pyrroles

The organophosphine catalyzed reaction of activated alkynes with isocyanides produces the corresponding heteroaromatization products, pyrroles, regioselectively in good yields. The reaction proceeds most probably through the 1,4-addition of the nucleophilic phosphine catalyst to the alkynes, followed by a [3+2] cycloaddition between the resulting alkenyl phosphine intermediates and a carbanion derived from the isocyanides.     

Copper-catalyzed vinylation of hydrazides. A regioselective entry to highly substituted pyrroles

A modular route to highly substituted pyrroles has been developed. This transformation consists of two sequential copper-catalyzed vinylations of bis-Boc-hydrazine followed by thermal rearrangement/cyclization. A wide variety of functionalized pyrroles can be prepared in a selective manner from simple and easily accessible precursors. [reaction: see text]     

Iron catalyzed highly regioselective dimerization of terminal aryl alkynes

Iron can catalyze head-to-head dimerization of terminal aryl alkynes to give the corresponding (E) selective conjugated enynes in high yields. A variety of substituted aryl acetylenes underwent smooth dimerization using catalytic FeCl(3) and DMEDA in the presence of KO(t)Bu.     

A facile synthesis of polysubstituted pyrroles

alpha-Aminoalkylcuprates prepared from CuX.2LiCl (X = Cl, CN) and 1 equiv of an alpha-lithiocarbamate undergo conjugate addition reactions to alpha,beta-alkynyl ketones in moderate to good yields, affording E:Z mixtures of alpha,beta-enones. Treatment of the conjugate adducts with PhOH/TMSCl in CH(2)Cl(2) effected carbamate deprotection and cyclization to afford a flexible two-step synthesis of substituted pyrroles.     

Zeolite-assisted regioselective synthesis of dinitronaphthalene

The nitration selectivity of naphthalene was studied in different organic solvents with 95 % fuming nitric acid as nitration reagent. The yield of dinitronaphthalene can achieve 78 % in hexane. With nitrogen dioxide as nitration reagent in oxygen, the selectivity of dinitronaphthalene in different types of molecular sieve catalyst was studied. When HBEA zeolite catalyst was used, the yield of dinitronaphthalene was up to 61 %. This method is easy to carry out, environmentally benign, and economical.