Rh（III）催化的N-甲氧基苯甲酰胺系列物选择性C-H氰基化反应

采用了最近热门的Rh(III)催化C?H键活化方法,以N-甲氧基苯甲酰胺系列物为反应底物, N-氰基-N-苯基对甲苯磺酰胺(NCTS)为氰基化试剂,高效合成了含氰基官能团产物。结果表明,该反应在碳酸银存在下,使用二氧六环作为反应溶剂,于80°C反应8h生成的邻位氰基取代的N-甲氧基苯甲酰胺的产率较高。进一步研究表明,该反应具有好的区域选择性和底物/官能团适应性。一系列机理实验研究表明,该反应可能采用了一个内部的亲电取代机制及使用了C?H键切割步骤作为关键限速步骤。考虑到该反应产物包含有价值的结构单元-N-甲氧基甲酰胺和氰基取代基,因而有望用于现代有机合成中。     

Montmorillonite clay catalyzed alkylation of pyrroles and indoles with cyclic hemi-acetals

Cyclic hemiacetals such as 2-deoxy-d-ribose and 2-deoxy-d-glucose react smoothly with pyrroles and indoles on the surface of montmorillonite KSF clay under extremely mild reaction conditions to afford optically active di-pyrrolyl and bis-indolyl alkanols in good yields with high selectivity.     

Metal-free direct arylations of indoles and pyrroles with diaryliodonium salts

Direct arylations of indoles and pyrroles with differently substituted diaryliodonium salts were shown to efficiently proceed in the absence of metal catalysts.     

Palladium catalyzed cyanation of o-dichloroarenes with potassium hexacyanoferrate(ii)

Cyanation of o-dichloroarenes with potassium hexacyanoferrate(ii) catalyzed by Pd(OAc)₂/PPh₃ system gave the corresponding phthalodinitriles in moderate yields. The method of competitive reactions revealed that activation rate of chloroarenes by Pd-catalyst increased in the presence of the electron-withdrawing groups in the arene core.     

Sulfenylation of some pyrroles and indoles

Methylsulfenylation of 1-substituted pyrroles and indoles was observed using 1-(methylthio)morpholine and an acid catalyst or with methylsulfenyl chloride and excess pyridine. 1-Substituents which are activating or weakly deactivating towards electrophilic substitution such as alkyl, 2-cyanoethyl, dimethylamino, trialkylsilyl, 2-chloroethyl and 2-phenylsulfonylethyl were used. The 2-chloroethyl and 2-phenylsulfonylethyl groups which can be removed with a strong base can be used to obtain 1H-methylthiopyrroles and indoles. 1-Phenylsulfonyl and 1-acetyl substituents are too strongly deactivating for these sulfenylations to be successful. Mono and disubstituted pyrroles and monosubstituted indoles can be isolated from these reactions, however, because the methylthio group is activating towards electrophilic substitution the main advantage of these reactions is the synthesis of tri and tetrasubstituted pyrroles and disubstituted indoles. 1-Methyl-2,3,4,5-tetra-methylthiopyrrole and 1-methyl-2,3-dimethylthioindole are oxidized to the corresponding 3,4-disulfoxide and 3-sulfoxide and with excess oxidizing agent to the tetrasulfone and disulfone, respectively.     

Rh2(S-biTISP)2-catalyzed asymmetric functionalization of indoles and pyrroles with vinylcarbenoids

Asymmetric functionalization of N-heterocycles by vinylcarbenoids in the presence of catalytic amounts of Rh(2)(S-biTISP)(2) has been successfully developed. This bridged dirhodium catalyst not only selectively enforces the reaction to occur at the vinylogous position of the carbenoid but also affords high levels of asymmetric induction.     

Ruthenium-catalyzed functionalization of pyrroles and indoles with propargyl alcohols

Several ruthenium-catalyzed atom-economic transformations of propargyl alcohols with pyrroles or indoles leading to alkylated, propargylated, or annulated heteroaromatics are reported. The mechanistically distinct reactions are catalyzed by a single ruthenium(0) complex containing a redox-coupled dienone ligand. The mode of activation regarding the propargyl alcohols determines the reaction pathway and depends on the alcohols' substitution pattern. Secondary substrates form alkenyl complexes by a 1,2-hydrogen shift, whereas the transformation of tertiary substrates involves allenylidene intermediates. 1-Vinyl propargyl alcohols are converted by a cascade allylation/cyclization sequence. The environmentally benign processes are of broad scope and allow the selective synthesis of highly functionalized pyrroles and indoles generating water as the only waste product.     

An improved method for Lewis acid catalyzed phosphoryl transfer with Ti(t-BuO)4

Several inorganic esters have been evaluated as phosphoryl transfer catalysts. Of these, Ti(t-BuO)(4) was found to be the most effective catalyst giving excellent yields of the desired phosphate esters. The loading of the catalyst could be reduced to a little as 5 mol % for a majority of substrates with no loss in the yield of product. This methodology is significantly more versatile than using TiCl(4) and is suitable for the phosphorylation of more complex carbohydrates and molecules of biological interest.     

Palladium-catalyzed synthesis of N-vinyl pyrroles and indoles

A stereospecific palladium-catalyzed N-vinylation of azaheterocycles with vinyl triflates is described. Cyclic and acyclic vinyl triflates along with nonnucleophilic azaheterocycles were found to be substrates for this palladium-catalyzed synthesis of N-vinyl pyrrole and indole derivatives.     

Reaction of 2-dicyanomethyleneindan-1,3-dione with pyrroles and indoles

The reaction of 2-dicyanomethyleneindan-1,3-dione with pyrrole, indole, and their methyl derivatives gives products of addition at the dicyanomethylene carbon atom, viz., pyrrolyl- and indolyl(1,3-dioxo-2-indanyl)malononitriles, which upon heating or irradiation with UV light irreversibly split out HCN to give deeply colored products of replacement of the nitrile group in the acceptor by a heterocyclic grouping. Data from the UV and PMR spectra of the compounds obtained are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 500–503, April, 1982.     

Cross-dehydrogenative coupling of secondary benzylic ethers with indoles and pyrroles

Current studies on cross-dehydrogenative coupling of benzylic ethers for new C–C bond construction predominantly focus on primary ether moieties. Oxidative cross-coupling of secondary benzylic ethers remains elusive. Herein, we describe the first cross-dehydrogenative coupling of secondary benzylic ethers with indoles and pyrroles for tertiary ether construction. A broad range of α-aryl substituted isochromans react with a variety of electronically varied indoles and pyrroles smoothly under mild metal-free conditions in high efficiency. In addition, the catalytic asymmetric variant was preliminarily explored, and corresponding tertiary ether was obtained in 69% ee.     

Lewis acid catalyzed nenitzescu indole synthesis

A novel method for Lewis acid catalyzed Nenitzescu indole syntheses of 5‐hydroxyindoles bearing different substituents in positions 1 )Alk, Bn, Ar), 2 )Me, Et, Ph), and 3 )COOEt, COMe, CONHPh) as well as tricyclic derivatives are reported. The method is simple, rapid, efficient, and allows preparation of hydroxyindoles from 1,4‐benzoquinone and enamines in good to excellent yields with the use of low‐polar solvents in the presence of weak Lewis acids catalysts. The formation of 5‐hydroxyindoles under such mild conditions is explained in terms of a non‐redox mechanism.     

The highly enantioselective addition of indoles and pyrroles to isatins-derived N-Boc ketimines catalyzed by chiral phosphoric acids

The first asymmetric aza-Friedel-Crafts reaction of indoles and pyrroles with isatin-derived N-Boc ketimines catalyzed by chiral phosphoric acids is reported. In general, derivatives of substituted 3-amino-2-oxindoles were obtained with excellent enantioselectivities and high yields.     

Lewis acid catalyzed intramolecular Diels-Alder reactions of acyclic (Z)-substituted 1,3-dienes

Lewis acid catalyzed intramolecular Diels-Alder reactions of trienes (E,E,Z)-1a-d, (E,E,Z)-4a-d, and (E,Z,Z)-7a,b are described. Trienes containing enal or enone dienophiles cyclize in excellent yield under mild conditions using substoichiometric amounts of MeAlCl(2), in most cases with high levels of diastereoselectivity. The thermal IMDA reactions of 1a, 4a, and 7a require forcing conditions and proceed in low yield with reversed stereoselectivity in the cases of 1a and 4a.     

Regiospecific C-acylation of pyrroles and indoles using N-acylbenzotriazoles

Reactions of pyrrole (2) or 1-methylpyrrole (4) with readily available N-acylbenzotriazoles 1a-g (RCOBt, where R = 4-tolyl, 4-nitrophenyl, 4-diethylaminophenyl, 2-furyl, 2-pyridyl, 2-indolyl, or 2-pyrrolyl) in the presence of TiCl(4) produced 2-acylpyrroles 3a-g and 5a-g in good to excellent yields. 1-Triisopropylsilylpyrrole (6) under the same conditions gave the respective 3-acylpyrroles 7a-g. Similarly, indole (9) and 1-methylindole (11) gave the corresponding 3-acylated derivatives 10a-g and 12a-g. These results demonstrate that N-acylbenzotriazoles such as 1c,f,g are mild, regioselective, and regiospecific C-acylating agents of particular utility when the corresponding acid chlorides are not readily available.     

Thermolytic removal of t-butyloxycarbonyl (BOC) protecting group on indoles and pyrroles

The t-Butyloxycarbonyl (BOC) group on indoles and pyrroles can be removed cleanly and in high yield by simple thermolysis: no acid, no base, no solvent is required.     

The development of new monometallic bifunctional catalysts with Lewis acid and Lewis base properties, and their application in asymmetric cyanation reactions

Bifunctional catalysts can drastically improve the efficiency of asymmetric processes with respect to enantioselectivity and/or conversion rate. A new type of chiral bifunctional catalyst has been developed recently in the Shibasaki group that contains both Lewis acid and Lewis base moieties. These monometallic and bifunctional phosphinoyl-containing catalysts are able to coordinate both nucleophilic and electrophilic substrates in the transition state. Several successful applications of this new catalytic concept in the field of asymmetric cyanation reactions have already been reported, for example, the asymmetric hydrocyanation of aldehydes and imines as well as the asymmetric Reissert reaction. The development and principle of this catalytic concept as well as main applications thereof are reviewed in this article.     

Lewis acid catalyzed substitution of allylic nitro compounds with cyanotrimethylsilane

The nitro group in allylic nitro compounds is replaced by cyano group on treatment with cyanotrimethylsilane in the presence of Lewis acid.