Synthesis of mono N-trifluoroethylated cyclic dipeptides

Trifluoroethylated N-termini in linear dipeptides l-TyrXOR [X = Gly, d-Ala, l-Leu, l-Phe, and l-Glu; R = H, Me, Et] exhibit sufficient nucleophilicity to give piperazine-2,5-dione ring formation through intramolecular cyclization reaction in acidic aqueous solutions. The reactions occur in high yield and with absolute configuration retention.     

A new approach to cyclic hydroxamic acids: Intramolecular cyclization of N-benzyloxy carbamates with carbon nucleophiles

N-Alkyl-N-benzyloxy carbamates, 2, undergo facile intramolecular cyclization with a variety of carbon nucleophiles to give functionalized five- and six-membered protected cyclic hydroxamic acids, 3, in good to excellent yields. This method can be extended to prepare seven-membered cyclic hydroxamic acids in moderate yields. The sulfone intermediates 3 from this study can be alkylated while the corresponding phosphonates have been shown to undergo HWE reaction. The α,β-unsaturated synthon, 8, prepared by thermal elimination of sulfoxide 3m, undergoes Michael addition with secondary amines. The usefulness of this approach to prepare polydentate chelators has been demonstrated by the synthesis of bis cyclic hydroxamic acids 12, 14, and 15.     

Catalyst-free concise synthesis of multi-functional 3-cyano-4-quinolinone derivatives from cyanoacetylenaminones and DMF-DMA

An efficient one-pot synthesis of 3-cyano-4-quinolinone derivatives has been developed via the intramolecular cyclization of cyanoacetylenaminones 1 with N,N-dimethylformamide dimethyl acetal (DMF-DMA) 2 under catalyst-free conditions in CH₃CN. The reaction offers several advantages, including operational simpleness, easily available starting materials, target molecular diversity, and facile purification. Additionally, the 3-cyano substituted quinolinones may undergo further functionalization and assist in the discovery of novel drugs.     

A facile electrochemical method for the synthesis of new sulfonamide derivatives of potential biological significance

The electrochemical synthesis of some new sulfonamide derivatives was carried out via the electrochemical oxidation of 2,3-dihydrophthalazine-l,4-dione （1） in the presence of arylsulfinic acids （2a and 2b） as nucleophiles. The results show that, the electrogenerated phthalazine-l,4-dione （lox） participates in a Michael type addition reaction with 2a or 2b and via an EC mechanism to produce the corresponding sulfonamide derivatives. This method provides a one-pot procedure for the synthesis of new sulfonamide derivatives of potential biological significance in good yields without using toxic reagents at a carbon electrode in an environmentally friendly manner.     

Sulfamic acid andN-alkylsulfamates in the synthesis of nitro derivatives of guanidine and aminofurazan

TheN-nitro derivatives of the products of the condensation of formaldehyde with sulfamic acid derivatives and guanidine, nitroguanidine, 3,4-diaminofurazan, and 3-amino-4-methylfurazan have been synthesized.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 719–721, April, 1995.     

A facile synthesis of novel tricyclic 4-pyridones

A new and efficient synthesis of tricyclic 4-pyridone analogs through the intramolecular Heck coupling cyclization was described. This reaction features mild conditions and good functional group tolerance allowing for the preparation of several novel tricyclic 4-pyridone analogs.     

A novel approach to the synthesis of diaza-bridged heterocycle derivatives

A novel synthetic route of diaza-bridged heterocycles based on natural 3,9-diazabicyclo[3.3.1]non-6-ene scaffold has been accomplished. The synthetic approach consists of a Pictet-Spengler condensation of the l-Dopa-OMe with an appropriate aldehyde, Fmoc-Aa-H, followed by intramolecular lactamization. This approach generated two configurationally distinct products (cis and trans-isomers), increasing the stereochemical diversity of these compounds. The synthesized compounds are potentially useful in the discovery of novel pharmacologically active compounds.     

A facile preparation of tetralins from arene-1,4-diones using titanium(IV) chloride and triethylsilane

A facile method for the synthesis of tetralins has been described which uses various substituted phenylpentane-1,4-diones as starting material with a combination of TiCl₄/Et₃SiH. The synthesis involves three reactions under mild conditions. A mechanism has been proposed for the reductive cyclization through ionic hydrogenation, and titanium(IV) chloride catalyzed cyclization.     

Palladium-catalyzed intramolecular 5-endo-trig oxidative Heck cyclization: a facile pathway for the synthesis of some sesquiterpene precursors

An efficient and convenient method for the construction of substituted cyclopentenones via palladium-catalyzed intramolecular 5-endo-trig oxidative cyclization has been introduced as a powerful new strategy for the synthesis of sesquiterpenes.     

Total synthesis of (+)-cylindricine C

A stereoselective total synthesis of (+)-cylindricine C has been achieved starting with (S)-N-Boc-2-pyrrolidinone. The key elements of this synthesis involve the sequence of reactions including BF₃-mediated addition of the allyl Grignard reagent to the cyclic imine, spirocyclization via enamine formation, and intramolecular Michael addition to form the tricyclic core.     

Electrosynthesis of hydroquinonethioethers using electrochemical oxidation of hydroquinone in the presence of thiouracil derivatives

Electrochemical oxidation of hydroquinone(1a) has been studied in the presence of 6-methyl-2-thiouracil(3a) and 6-propyl-2-thiouracil(3b) as nucleophiles in a DMF/buffer mixture,using cyclic voltammetry and controlled-potential coulometry.The results indicated that the p-quinone(2a) derived from 1a participates in a 1 4-Michael addition reaction with the thiouracil derivatives(3a–b) to form the corresponding hydroquinonethioether derivatives(6a–6b).The electrosynthesis of these compounds(6a–b) has been successfully performed on carbon rod electrodes in an undivided cell in good yield and purity.     

A synthesis of crambescidin 359

A potentially biomimetic synthesis of the guanidine-containing marine natural product crambescidin 359 via a double Michael addition of guanidine to a suitably functionalised bis-enone is reported.     

A facile synthesis of indolo[3,2,1-jk]carbazoles via palladium-catalyzed intramolecular cyclization

A new efficient synthesis of indolo[3,2,1-jk]carbazoles by the palladium-catalyzed cyclization of N-(2-bromoaryl)carbazoles is described. The reaction involves intramolecular C-C bond formation, coupled with the cleavage of a C-X bond and a C-H bond on carbazole ring. Substitutions on N-aryl core with either electron-donating or electron-withdrawing groups are introduced, and different reaction factors for cyclization are evaluated.     

C2轴手性双胍催化叶立德和不饱和吖内酯的串联反应研究

本文成功合成了4种基于联二萘酚骨架的手性双胍-酰胺类催化剂,并将其应用于邻羟基苯甲醛亚甲胺叶立德与不饱和吖内酯的1,3-偶极环加成和分子内串联反应。研究表明,在室温下以CHCl_3作为溶剂、轴手性胍(1b,10(mol)%)作为催化剂,反应12h,能以较好的收率(73%～88%)和较高的对映选择性(72%～86%)得到苯并吡喃衍生物。     

Chiral guanidine catalyzed Michael addition reaction and Diels-Alder reaction of anthrone and N-methylmaleimide

Two chiral guanidines were evaluated as catalysts for the reaction of anthrone (1) with N-methylmaleimide (2). When guanidine 5 was used, the Michael adduct 4 was isolated as a major product. The best enantioselectivity (70% ee) was obtained when the reaction was carried out in THF at - 20℃.     

A facile intramolecular azido/amido reductive cyclization approach: synthesis of pyrrolobenzodiazepines and their dimers

A new synthetic pathway has been developed for the preparation of imine-containing pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) and their dimers. Selective reduction of aromatic azides as well as aliphatic amides in a single step leading to an intramolecular reductive cyclization process by employing LiAlH₄ or LiBH₄ provides the cyclized imines.     

Microwave-assisted preparation of cyclic ureas from diamines in the presence of ZnO

A microwave-assisted facile method for the preparation of various ureas, cyclic ureas, and urethanes has been developed that affords nearly quantitative yield of products at 120 °C (150 W), 71 kPa within 10 min using ZnO as a catalyst. The enhanced selectivity in this reaction is attributed to the deployment of ZnO whose absence results in poor yield and the generation of byproducts.     

Facile and straightforward synthesis of the racemic version of 2-amino-4H-chromene-3-carbonitriles using K2HPO4 as an eco-friendly base

A simple and facile two-step synthetic route has been developed for the preparation of 2-amino-4H-chromenes via chalcone intermediate under an ambient condition, along with the crystallographic analysis of the racemic mixture so obtained. The crystal orientation can be very useful for generic drug development in future. The described non-hazardous optimized methodology also provides an alternative simple route to prepare functionalized 2-amino-4H-chromenes of biological interest.     

Water-compatible one-pot organocatalytic asymmetric synthesis of cyclic nitrones. Application in intramolecular 1,3-dipolar cycloadditions

Optically active five-membered cyclic nitrones are readily obtained in a one-pot procedure via the organocatalytic Michael addition of aldehydes to nitroolefins and in situ reductive cyclization. Application of the methodology to the synthesis of tricyclic compounds through intramolecular 1,3-dipolar cycloaddition reactions (DFT calculations have also been performed) is also demonstrated. All the reactions were carried out in water as a solvent and excellent ee values (ee >99%) were obtained.