Ullmann-type C–N coupling reaction catalyzed by CuI/metformin

A facile and efficient method for Ullmann-type C–N coupling reaction of amine and aryl halide catalyzed by CuI/metformin in EtOH is described. The advantages of this method are the use of an inexpensive and readily available catalyst and ligand, easy workup, shorter reaction time, improved yields, and the use of green solvent. Furthermore, this procedure is applied successfully for the modification of natural products, such as Vindoline and Tabersonin.     

Facile synthesis of 2,5,7-trisubstituted oxazolo[5,4-d]pyrimidines via copper-catalyzed intramolecular C–O bond formation

A novel and convenient synthesis of 2,5,7-trisubstituted oxazolo[5,4-d]pyrimidines was presented. The key step involved an intramolecular C–O cross-coupling of the ortho-halopyrimidine amide via a copper (I)-mediated cyclization reaction, which provided target trisubstituted oxazolopyrimidine in moderate to good yields.     

Silver-mediated intramolecular P–C coupling

Silver(I) salts mimic copper(I) but not gold(I) salts in the reaction with peri-iodo naphthyldiisopropylphosphine. The formation of the corresponding peri-cyclic phosphonium derivatives represents the first example of silver-mediated P–C coupling through a two-electron redox sequence.     

CuI catalyzed domino coupling–cyclization of 2-iodo-phenols and 1-alkynes to the synthesis of 2-substituted benzo[b]furans/furo-pyridines

CuI/proline-catalyzed coupling reaction of 2-iodo-phenols with terminal alkynes and the following cyclization process is carried out successively in DMSO at 80?°C. Under this tandem process, 2-substituted benzo[b]furans/furo-pyridines were synthesized in good to excellent yields with a great diversity.     

A gram-scale synthesis of multi-substituted arenes via palladium catalyzed C–H halogenation

(6-Amino-2-chloro-3-fluorophenyl)methanol is prepared through both traditional methods and palladium catalyzed iterative C–H halogenation reactions.In comparison to traditional approach,the C–H functionalization strategy demonstrated a few advantages including milder reaction conditions higher yields,better selectivity and practicality,and high chemical diversity.     

I2–DMSO catalyzed synthesis of 1,2,2-triarylethanones via dual C–H activation of aryl methyl ketones

An I₂–DMSO promoted domino protocol was developed for the synthesis of 1,2,2-triarylethanones from readily available aromatic methyl ketones and methoxybenzenes. The 1,2,2-triarylethanones are important precursors for the synthesis of Tamoxifen and Droloxifene. The use of mild reaction conditions, high yield, and single step synthesis are the advantages of the present protocol.     

Microwave assisted synthesis of 2-aminooxazolo [4,5-b] pyridine derivatives via intramolecular C–O bond formation in aqueous medium

A highly, efficient synthetic protocol for the synthesis of 2-aminooxazolo[4,5-b]pyridine derivatives is established via intramolecular C–O bond coupling using copper iodide as a catalyst and water as solvent. A variety of functionalized substrates were found to react under this reaction conditions to provide products in good to excellent yields.     

Pd(II)-catalyzed intramolecular C–H activation/C–C cross coupling for the synthesis of carbazoles from diaryl acetamides

Pd(II)-catalyzed intramolecular C–H activation/C–C cross coupling within N,N-diphenyl-acetamides allows the efficient formation of differently substituted carbazoles. In this cross-dehydrogenative coupling, many different functional groups are tolerated and the starting material N,N-diphenyl-acetamides can be easily prepared in one step from commercially available acetanilides and iodobenzenes.     

Synthesis of π-extended porphyrins via intramolecular oxidative coupling

Porphyrins fused with other aromatic units at the meso- and β-positions have recently emerged as a hot topic of research. Their synthesis typically starts with preparation of precursors via either Suzuki coupling of a meso-bromoporphyrin or mixed-aldehyde condensation, and is followed by oxidative aromatic coupling, often using high-valent metal reagents (DDQ/Sc(OTf)(3) and Fe(iii) salts are among the most popular). In recent years, porphyrins were oxidatively coupled not only with well-known aromatic hydrocarbons such as naphthalene and pyrene, but also with more complex heterocyclic fragments, including indole, phenanthro[1,10,9,8-cdefg]carbazole and BODIPY. A subtle relationship exists between the output of intramolecular oxidative coupling and the nature of the second aromatic moiety, cation in the porphyrin cavity, oxidant, and type of remaining meso-substituent. The extension of the porphyrin chromophore leads to significant change in linear and non-linear optical properties. Very strong bathochromic shifts of absorption (λ(max) reaching 1.5-2 microns in some cases) and increases in two-photon absorption cross-sections are typical for these functional dyes.     

A tandem and tunable Pd catalyzed C–N coupling of heteroarenols with ureas via C–OH bond activation

At this circumstance for the first time, a facile and convenient method for heteroaryl ureas has been developed via a two-step process involving in situ C–OH activation followed by palladium catalyzed C–N coupling of heteroarenols with ureas, which show excellent functional group tolerance and give out rapid coupling in good to excellent yield.     

Facile synthesis and functionalization of fluoranthenes via intramolecular [4 + 2] annulations between thiophenes and alkynes

Fluoranthenes have attracted tremendous attention due to their unique optoelectronic properties and extensive applications. Although several synthetic methodologies have been developed for the preparation of fluoranthene derivatives, it is still unfavorable to functionalize the fluoranthene framework at different positions due to the relatively low selectivity and reactivity. Herein, a catalyst-free intramolecular [4 + 2] annulation between thiophenes and alkynes is developed towards the synthesis of fluoranthenes. Altogether 20 examples have been demonstrated using this method. Various functional groups can be precisely introduced into the fluoranthene skeleton at different positions by simply tuning the substituents on the thiophenes and alkynes. The conjugation of the fluoranthene can be facilely extended through different directions. Furthermore, the feasibility of this [4 + 2] annulation reaction is also investigated by density functional theory calculations. Therefore, this protocol provides not only a synthetic methodology towards fluoranthenes with substituents functionalized at different positions, but also an effective pathway to construct large polycyclic aromatic hydrocarbons containing fluoranthene moieties.     

Transition metals catalyzed C–C and C–O bonds formation: facile synthesis of flavans and benzoxepines

A simple and practical method has been developed based on intermolecular [Pd]-catalyzed C–C and an intramolecular [Cu]-catalyzed C–O bond formations for the synthesis of flavans and benzoxepines. Interestingly, the method is amenable for the synthesis of a wide variety of flavans and benzoxepines with dense functionalities on aromatic moieties. Significantly, flavans and benzoxepines are present as core/part-structures in many biologically active natural products.     

Facile synthesis of azaarene-substituted 3-hydroxy-2-oxindoles via Brønsted acid catalyzed sp3 C-H functionalization

Br?nsted acid catalyzed functionalization of sp(3) C-H bonds in 2-methyl azaarenes has been achieved in the reaction with isatins. This method provides facile synthesis of biologically important azaarene-substituted 3-hydroxy-2-oxindoles in one step in moderate to good yields.     

Efficient synthesis of diversely substituted pyrimidines by palladium catalyzed Suzuki–Miyaura coupling

An efficient synthesis of 2-aryl/heteroaryl substituted pyrimidinyl ethanones 4(a–t) was developed using a palladium-catalyzed Suzuki–Miyaura coupling reaction strategy. Use of Pd(OAc)₂ in the presence of PPh₃ and Na₂CO₃ in 1,4-dioxane solvent was found to be the most effective reaction condition.     

Synthesis of bicyclic lactones via I2-mediated intramolecular tandem C–C/C–O bond formation

The iodine/DMAP-mediated intramolecular tandem C–C/C–O bond forming reaction of malonate bearing alkene moiety proceeded to give bicyclic lactones with good diastereoselectivity in good yield. The mechanistic investigation was also discussed on the basis of various control experimental results.     

Copper-catalyzed intramolecular C–N coupling reaction of aryl halide with amide

An efficient and concise method for the ligand-free copper-catalyzed intramolecular C–N bond coupling was developed, which afforded various (NH)-phenanthridinones in good to excellent yields with tolerance of various substrates.     

Novel iodine catalyzed diastereoselective synthesis of trans-2,6-disubstituted tetrahydro-2H-pyrans: synthesis of C1–C13 fragment of bistramide-A

A new method for the stereoselective synthesis of trans 2.6-disubstituted tetrahydro-2H-pyrans has been developed involving iodine catalyzed allylation of tetrahydro-2H-pyranol with excellent trans selectivity. The method was also applied toward the construction of C1–C13 fragment of bistramide-A in 11 steps with 21.4% overall yield.     

One-pot synthesis of symmetrical dinucleoside polyphosphates and analogs via 4,5-dicyanoimidazole-promoted tandem P–O coupling reactions

A novel one-pot protocol for the synthesis of symmetrical dinucleoside tri-, tetra-, and pentaphosphates, and their phosphonate analogs simply from nucleoside 5′-phosphoropiperidates has been developed by utilizing 4,5-dicyanoimidazole-promoted tandem P–O coupling reactions.     

Facile synthesis of coumarin bioisosteres—1,2-benzoxathiine 2,2-dioxides

A simple and reproducible procedure for the synthesis of bioisosteres of coumarin—1,2-benzoxathiine 2,2-dioxide is presented. The developed method is based on the intramolecular aldol cyclization of derivatives of mesylsalicyl aldehydes in the presence of strong organic bases, where best results were obtained with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). It has been shown that depending on the nature of the substituent in the aromatic ring, intermediate aldol adducts (3,4-dihydro-1,2-benzoxathiin-4-ol 2,2-dioxides) in different ratios with title compound are formed. Dehydration of the intermediate aldols with POCl₃ led to full conversion into 1,2-benzoxathiine 2,2-dioxide derivatives. The scaffold of 1,2-benzoxathiine 2,2-dioxide is unequivocally proven by a single-crystal X-ray structure.     

Asymmetric synthesis of N-phenylethyl-2-phenyldecahydroquinolin-4-ones via Lewis acid catalyzed imino-Diels–Alder reaction

The asymmetric synthesis of N-phenylethyl-2-phenyldecahydroquinolin-4-ones was performed via a Lewis acid catalyzed imino-Diels–Alder reaction between the enantiopure (R)-N-phenylethylbenzylideneimine and the trimethylsilyl enol ether of acetylcyclohexene. The regio- and stereoselective formation of intermediary bicyclic enoxysilanes, followed by their stereoselective protonation was evidenced. The initial stereoselectivity was kept only if the reaction mixture was treated using controlled basic conditions. Three enantiopure title compounds were isolated with a 5–15% yield.