An efficient synthesis of 6,9-disubstituted purin-8-ones via copper-catalyzed coupling/cyclization

An efficient and novel synthesis of 6,9-disubstituted purin-8-ones has been developed. Starting from dichloropyrimidin-5-ylcarbamate, CuCl/amino acid catalyzed coupling/cyclization reaction with amines was achieved to afford 9-substituted 6-chloropurin-8-ones. Then a microwave-assisted amination procedure was carried out for the synthesis of 6,9-disubstituted purin-8-ones in moderate to good yields.     

An efficient synthesis of indoles via a CuMgAl-LDH-catalyzed cyclization of 2-alkynylsulfonanilides

A highly efficient method for the synthesis of indoles has been successfully developed via a CuMgAl-LDH-catalyzed intramolecular annulation reaction of 2-alkynylsulfonanilides. This CuMgAl-LDH catalyst features facile preparation, recovery, and reuse at least seven times without a marked loss in the catalytic activity, as well as the unique dual activation. Moreover, the crystal structures and Hirshfeld surface analysis of typical indole compounds were also presented.     

An efficient and practical synthesis of 2,4-substituted pyrido[4,3-d]pyrimidin-5(6H)-ones

We describe an efficient synthesis of 2,4-substituted pyrido[4,3-d]pyrimidin-5(6H)-ones, which involves the acid-promoted cyclization of cyano enamine 15 to afford 2,4-bis(methylthio)pyrido[4,3-d]pyrimidin-5(6H)-one 17 as a key intermediate. Selective displacement of the 4-methylthio group by a wide range of anilines followed by oxidation of the 2-methylthio group and subsequent substitution by amines enabled the synthesis of a variety of 2,4-disubstituted pyrido[4,3-d]pyrimidin-5(6H)-ones.     

室温下三光气作环合剂合成5-取代-1,3,4-噁二唑-2-酮类化合物

1,3,4-噁二唑具有抗菌,抗肿瘤,抗惊厥等生物活性~([1-6]),在药物化学方面具有重要的理论意义和实际应用价值.1,3,4-噁二唑类材料具有优良的荧光性和闪烁性和优异的电子传输性能,以及特殊的稳定性和良好的耐热性,被认为是下一代显示器件中载流子输送的首选材料~([7-8]).     

An efficient synthesis of dihydro- and tetrahydropyrans via oxonium-ene cyclization reaction

An efficient method has been developed for the synthesis of 2,3-dihydropyrans and 4-methylenetetrahydropyrans from aldehydes and substituted homoallyl alcohols in benzene mediated by boron trifluoride etherate in good yields. The reaction proceeds via oxonium-ene reaction.     

Efficient synthesis of highly substituted Pyrrolin-4-ones via PIFA-mediated cyclization reactions of enaminones

A convenient and efficient synthesis of highly substituted pyrrolin-4-ones is developed via the PIFA-mediated cyclization reactions of readily available enaminones, and a mechanism involving sequential cleavage of N-C bond, formation of new N-C bond, intramolecular addition reaction, and benzilic acid type rearrangement is proposed.     

Synthesis of seven-membered ring diazepin-2-ones via palladium-catalyzed highly regioselective cyclization of 2-vinylpyrrolidines with aryl isocyanates

The first palladium-catalyzed ring-expansion reaction of 2-vinylpyrrolidines with aryl isocyanates to form seven-membered ring heterocycles is described. This regioselective reaction requires 5 mol % of Pd(2)(dba)(3).CHCl(3) and 10 mol % of dppp at 40-60 degrees C in THF and results in the formation of 1,3-diazepin-2-ones in good isolated yields. When Pd(OAc)(2) and PPh(3) were utilized in the reaction, an intramolecular hydrogen migration occurs resulting in the formation of conjugated diene derivatives of urea.     

Palladium-catalyzed carbonylative cyclization of Baylis-Hillman adducts. An efficient approach for the stereoselective synthesis of 3-alkenyl phthalides

A palladium-mediated carbonylative cyclization reaction of Baylis-Hillman adducts is disclosed. This simple, efficient and straightforward sequence leads to the formation of an array of 3-alkenylphthalides with different substitution patterns on the aromatic ring, with good chemical yields and selectivities.     

Silver-catalyzed highly efficient synthesis of pyrido[1,2-a]pyrimidin-4-ones from 2-aminopyridines and alkynoates

Pyrimidinone is one of the important nitrogen containing heterocycles due to their wide range of bioactivities. An efficient silver-catalyzed intermolecular cyclization of 2-aminopyridines with various alkynoates has been developed. 2-Substituted 4H-pyrido[1,2-a]pyrimidin-4-ones containing a wide range of functional groups are synthesized in the standard conditions. This transformation is conducted under convenient conditions and affords products in good yields.     

The synthesis of 1,2-diarylindenes via DDQ-mediated dehydrogenative intramolecular cyclization

A direct DDQ-mediated dehydrogenative intramolecular cyclization of (Z)-1,2,3-triaryl substituted propylenes promoted by Cu(OAc)₂ was developed, providing 1,2-diarylindene derivatives in moderate to good yields (up to 92%) under mild conditions. This protocol provides a straightforward access to 1,2-diarylindenes via DDQ-mediated benzylic/allylic sp³ C–H bond activation.     

Ruthenium-catalyzed cyclization of 3-en-1-ynyl imines with nucleophiles via tandem 5-exo-dig cyclization and nucleophilic addition

Treatment of 3-en-1-ynyl imines with TpRuPPh₃(CH₃CN)₂PF₆ catalyst (1 mol %) in DCE (50 °C, 6 h) effected catalytic cyclization with suitable nucleophiles and gave functionalized pyrroles in good yields. The reaction mechanism is proposed to proceed via (2-pyrrolyl)carbenoid intermediates derived from 5-exo-dig cyclization. This catalytic reaction works well with various nucleophiles, including water, alcohols and anilines.     

Effi cient synthesis of fused pyrazoles via simple cyclization of o-alkynylchalcones with hydrazine

The synthesis of pyrazole derivatives from o-alkynylchalcones and hydrazine via simple cyclization is described. This greener syntheticmethodology provides a straightforward approach to the synthesis of a variety of pyrazole derivatives under mild reaction condition.     

Palladium catalyzed Heck-arylation/cyclization cascade: An environmentally benign and efficient synthesis of 4-arylcoumarins in water

An environmentally benign and efficient approach for the synthesis of 4-arylcoumarins from ortho-hydroxy cinnamate ester derivatives with aryl iodides was developed in water under aerobic conditions. This transformation proceeds through a palladium catalyzed Heck-arylation/cyclization cascade reaction. The present protocol features a wide substrate scope and readily available starting materials to afford the desired products in high to excellent yields.     

An efficient synthesis of conjugated 5-aryl-1,3,4-oxadiazoles from 3-heteroarylacrylohydrazides and acid chlorides

New derivatives of 5-aryl-2-[2-(2-furyl)ethenyl]-1,3,4-oxadiazoles and 5-aryl-2-[2-(2-thienyl)ethenyl]-1,3,4-oxadiazoles are synthesized in a stepwise procedure through intermediate acyclic N′-arylcarbonyl-N-[2-(2-heteroaryl)acryloyl]hydrazines, starting from 3-(2-heteroaryl)acrylic acid hydrazides and acid chlorides. A facile one-pot methodology leading to the final 1,3,4-oxadiazoles is also described.     

Heterogeneous gold(I)-catalyzed cyclization between ynals and amidines: An efficient and practical synthesis of 2,4-disubstituted pyrimidines

A novel and highly efficient heterogeneous gold(I)-catalyzed cyclization between ynals and amidines has been developed that proceeds smoothly under mild conditions and provides a general and practical method for the synthesis of a wide variety of 2,4-disubstituted pyrimidines with high atom-economy, good to high yield, and recyclability of the gold(I) catalyst. The present method is an attractive alternative to construct substituted pyrimidines.     

An efficient synthesis of optically active physostigmine from tryptophan via alkylative cyclization

[reaction: see text] A new and efficient synthetic route to physostigmine is described. Corey-Kim reagent reacted with tryptamine or tryptophan carbamates to give 3a-(methylthiomethyl)hexahydropyrrolo[2,3-b]indole skeletons. Formal total synthesis of racemic and chiral physostigmine was accomplished in excellent overall yields, in short steps.     

An efficient synthesis of 2H-indazoles via reductive cyclization of 2-nitrobenzylamines induced by low-valent titanium reagent

An efficient and improved synthesis of 2H-indazoles via reductive cyclization of 2-nitrobenzylamines induced by low-valent titanium reagent (TiCl₄/Zn) is described. In this reaction triethylamine (TEA) was used to control the pH value. This method has the advantages of easily accessible starting materials, convenient manipulation, higher yield, shorter reaction time, and wider substrate scope.     

One-pot synthesis of 3-arylaminomaleimides from terminal alkynes and isocyanates

The reaction of aryl acetylide anions with phenyl isocyanate and subsequent addition of a protonating agent such as ethanol affords good yields of 3-aminomaleimides, formed by the cyclization of one molecule of alkyne with two isocyanates. When the reaction is quenched with water instead, cyclopentadienone imines are formed as the major products.     

Haloamidation of alkynes and related reactions using zirconacycles and isocyanates

Zirconacyclopentenes reacted with isocyanates to give aza- or oxazirconacycles which were conveniently coverted into the corresponding haloamidation products of alkynes after halogenation. 1,4-Bistrimethylsilyl substituted zirconacyclopentadiene afforded a low yield of iodoamidation product, whereas zirconium-alkyne complexes stabilized with phosphine gave the iodoamidation products in moderate yields. On the other hand, zirconacyclopentanes reacted with isocyanates to give trimerization products of isocyanate, isocyanurates.