Bischler-Napieralski Cyclization:A Versatile Reaction towards Functional Aza-PAHs and Their Conjugated Polymers

Nitrogen atom doped polycyclic aromatic hydrocarbons,the so-called aza-PAHs,and their conjugated polymers are applicable as functional chromophores and organic semiconductors.Prosperous developments of PAHs and heterocyclic chemistry have been made possible by considerable improvements in synthetic methodologies,among which one-step reactions leading directly to an aza-conjugated ring are highly desirable.Bischler-Napieralski cyclization,an old yet efficient reaction,can accomplish this task.During the last ten years,this reaction has been successfully used to synthesize a great variety of aza-PAHs molecules.Further combination with polymer chemistry is able to provide the corresponding polymers.This feature article summarizes the up-to-data advances,mainly achieved by our groups,on the design and synthesis of new and well-tailored aza-PAHs and macromolecular architectures using Bischler-Napieralski cyclization as the key step.Furthermore,the versatile applications of these functional materials in the fields of chemosensors,optoelectronic devices,and biomolecular probes are also covered in detail.

Synthesis of a highly hydrophobic cyclic decapeptide by solid-phase synthesis of linear peptide and cyclization in solution

A general method was described to synthesize a highly hydrophobic cyclic peptide,cyclo[LWLWLWLWLQ]where underlines indicate D-configuration of the amino acid,by a two-step solid-phase/solution synthesis strategy.The linear decapeptide was assembled by standard Boc chemistry on solid-phase and subsequently cyclized in solution with high efficiency and reproducibility. In subsequent purification by semi-preparative HPLC,50%(v/v) DMF/H_2O was employed as the solvent to overcome the difficulty of solubilization...

Rhodium-catalyzed selective[2+2+2]cyclizations of 1,6-diynes with monoynes leading to isoindolines and isobenzofurans

A highly efficient and selective[2+2+2]cyclization of diynes and monoalkynes was catalyzed by rhodium under room temperature in water/THF mixed solvent,affording isoindolines and isobenzofurans in good to excellent yields.The center atoms (N,O) in the diynes showed a significant effect for the cyclization.

The Mechanism on Cyclization, Debenzylation and Oxidation of 1-[1-(Benzyloxy)-3-methylnaphthalen-4-yloxy]propan-2-one

1-[1-（Benzyloxy）-3-methylnaphthalen-4-yloxy]propan-2-one （la） took place a cyclization, debenzylation and oxidation to form 9-substitued benzo[de]chromene-7,8-dione （2a） and 5-benzyl-9-substitued benzo[de]chromene-7,8-dione （3a）. The mechanisms for these reactions were discussed.

Stereoselective Functionalization at C-2 and C-3 of the Gibberellin via an Intramolecular Free Radical Cyclization Approach

Stereoselective functionalization at C-2 and C-3 of the gibberellin skeleton was achieved via an intramolecular free radical cyclization approach using a tethered C-19 halomethyl ester as the radical precursor.

N-Radical enabled cyclization of 1,n-enynes

Compared to the widely used carbon-centered radicals,N-radicals have been relatively unexplored owing to the lack of practical and convenient production methods.Over the past few years,benefitting from the resurgence of reliable and controllable radical chemistry,N-radicals have been produced via thermal decomposition,oxidants,metal salts,or electrocatalysis.Therefore,numerous N-radical enabled cyclization of 1,n-enynes methods have been developed,providing a versatile and concise synthetic platform for the preparation of complex cyclic systems and natural products containing elaborate ring frameworks.In this review,we will summarize recent advances in the promising field of radical chemistry focusing on the production methods of N-radicals and their cyclization patterns,associated mechanisms,unmet challenges,and future opportunities.

Oxidative Cyclization of Azo-coupling Products of 3-Isopropenyltropoloneand 3-Cinnamoyltropolone with Bromine

new method to synthesize heterocycle-fused troponoid compounds by oxidizing azocoupling products of 3-isopropenyltropolone and 3-cinnamoyltropolone with bromine in the presence of pyridine was reported for the first time. Reaction of azo-couping products of 3-isopropenyl tropolone 1a similar to f and 3-cinnamoyltropolone 3a similar to d with excess bromine afforded heterocycle-fused troponoid compounds 2a similar to f, 4a similar to d, respectively.

Ferric Chloride Catalyzed Isomerization and Cyclization of Geraniol, Linalool and Nerol

Ferric chloride catalyzes the isomerization and cyclization of geraniol, linalool and nerol in acetonitrile giving a-terpineol in good to high yields.

β-Lactam Templated Macrocyclization:Synthesis of 12-Membered Macrolide

A novel macrolactonization method was developed using a chiral β-lactam as the template. This novel method features that the macrocyclization is simultaneously achieved while a TBS protected hydroxy group is deprotected.

Cyclization and halogenation of substituted o-allylphenols with diacetoxyiodobenzene in the presence of iodine or bromine

Substituted 2-halomethyl-2,3-dihydrobenzofurans were synthesized in one pot and in mild yield from substituted o-allylphenols with diacetoxyiodobenzene in the presence of 12 or Br2 in dry CH2Cl2 under reflux.

Palladium-catalyzed Cascade Cyclization-Coupling Reaction of Benzyl Halides with N, N-Diallylbenzoylamide

A novel type of palladium-catalyzed cascade cyclization-coupling reaction has been found. Reaction of N, N-diallylbenzoylamide 1 with benzyl halides 2 afforded the corresponding dihydropyrroles 3 in moderate to excellent yields.

An Efficient Cationic Cyclization Approach for the Construction of Labdane Diterpenoid Decalin Ring Skeleton

An effective approach for the construction of the decalin ring skeleton of labdane diterpenoids was developed based on a key biomimetic cationic polyene cyclization of an epoxy allylsilane precursor. The synthetic approach demonstrated here would be useful in the enantioselective and diastereoselective total synthesis of natural labdane diterpenoids in general.

Study of Intramolecular Cyclization of N-styryl-oxo-cinnamides (Ⅱ)

The preparations and intramolecular cyclizations of amides 5, (N-methyl-N-(2 - trans-2-phenylethenyl)-3-phenyl-2, 3-cis-oxiranecarboxamide) and 8, (N-methyl-N-(2-cis-2-phenylethenyl ) - 3 -pheny 1-2, 3 - cis -oxiranecarboxamide) were reported.

Potassium Ferricyanide Oxidative Cyclizationof Arylaldehyde with o-Phenylenediamine and o-Aminophenol to 2-Arylbenzimidazoles and 2-Arylbenzoxazoles

Some new benzimidazoles and benzoxazoles have been prepared under mild condition by oxidative cyclization of arylaldehyde witho-phenylenediamine ando-aminophenol using potassium ferricyanide as oxidant

Cyclization Reaction of α-Triazolyl-α, β-unsaturated Ketones with Phenyl hydrazine

The reaction of α-triazolyl-α, β-unsaturated ketones with phenyl hydrazine was studied. The result indicated that cyclization took place and new heterocyclic compounds of substituted 4,5-2H-pyrazoles were obtained, whose structures and conformation were characterized by 1H NMR, IR, MS, elemental analysis and X-ray diffraction.

Polymer-support Selenium-induced Electrophilic Cyclization:Solid-phase Synthesis of Flavonoids

The Lewis acid mediated polystyrene supported selenium cyclization of chalcones and oxidative cleavage of selenium resins flavonoids in good yields and purities have been reported. induced intramolecular gave the corresponding

Synthesis of Asymmetric 4H-1, 3, 2-Benzodioxaphosphorin 2-Sulfides from Intramolecular Cyclization Reaction

Asymmetric 6-substituted-2-methoxy-4-(2,4-dichlorophenyl)-4H-1,3,2-benzodioxaphosphorin a-sulfides were prepared from intramolecular cyclization. The diastereomers were separated by column chromatography and fractional crystallization. Their structures were characterized on the basis of H-1 NMR, P-31 NMR and x-ray diffraction analysis.

AN ATTEMPT TO SYNTHESIZE HOMOCLAUSENAMIDE AND ZETACLAUSENAMIDE －Study of The Intramolecular Cyclization

Preliminary studies on the intramolecular cyclization of amides 11 and 15 in anatlempl to synthesize the natural Producls homoclausenamide 1 and zetaclausenamide 2 werereported.

Studies on the cyclization reaction of D-aspartic acid

The cyclization reaction of D-aspartic acid was studied, the carboxyl groups of D-aspartic acid were protected by benzyl alcohol to give compound D-dibenzyl aspartate. Then （4R）-benzyl azetidine-2-one-4-carboxylate and meso-3,6-disubstituted piperazine-2,5-diones were synthesized via intramolecular cyclization and intermolecular cycfization of D-dibenzyl aspartate, respectively, and their structures were confirmed by ^1 H NMR and MS. Both cyclization reaction conditions were also investigated in detail.

Facile Synthesis of [1,2,4]Triazolo[4,3-a]pyrazin-3-amines via Oxidative Cyclization of 1-(Pyrazin-2-yl)guanidine Derivatives

In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3-a ]pyrazin-3-amines. We optimized the reaction procedure to easily obtain 5-chloro-[1,2,4]triazolo[4,3-a ]pyrazin-3-amine. Various types of halogenated pyrazines can successfully undergo this process. We synthesized a series of 1-(pyrazin-2-yl)guanidines and [1,2,4]triazolo[4,3-a ]pyrazin-3-amines, and then elucidated their structures based on their ~1H-NMR, ^(13)C-NMR, ESI-HRMS, and nuclear Overhauser effect spectra.