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.

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.

The Cyclization Reactions of Lawesson's Reagent with Bifunctional Substrates

The cyclizaion reactions of Lawesson's reagent(LR) with the substrates containing two functional groups such as hydroxy groups,amino groups, has been applied to prepare the O-P-O,N-P-N type 5-membered and 6-membered phosphorus heterocycles.The heterocyclizaional possibility of LR with bifunctional compounds was also discussed.

Transition Metal Catalyzed Enantioselective Borylative Cyclization Reactions

Due to the significance of corresponding products,enantioselective borylative cyclization reactions have been studied intensively in recent years.Many groups have developed efficient methods to transform unsaturated system into asymmetric cyclic organoboron compounds with the ring-size range from three-membered to six-membered in general.Notably,in some cases,fused rings which contain more than two contiguous chiral centers could be obtained by this kind of strategies.This review summarized and reviewed the recent advances in this field and classified these work according to the species of metal catalysts.

Convenient and efficient access to tri-and tetra-substituted 4-fluoropyridines via a[3+2]/[2+1]cyclization reaction

A[3+2]/[2+1]cycloaddition reaction of gem–difluorocyclopropenes is presented,offering a mild and efficient approach to accessing tri-and tetra-substituted 4-fluoropyridines in moderate to good yields with excellent regioselectivity.Multiple synthetic applications,including process-scale reactions,modification of bioactive molecules,derivatization reactions and synthesis of the analogue of the PKM2 modulator,are subsequently described.

Organocatalytic asymmetric cascade cyclization reaction of o-hydroxy cinnamaldehydes with diphenylphosphine oxide

A highly stereoselective asymmetric cascade cyclization reaction between o-hydroxycinnamaldehydes and diphenylphosphine oxide has been achieved with 84%-99% ee and 7：1-20：1 dr under the catalysis of L-diarylprolinol silyl ether. This reaction provides a facile access to highly enantioenriched 4- diphenylphosphinyl chroman-2-ols. It also represents a novel organocatalytic asymmetric phospha- Michael addition of α,β-unsaturated aldehydes with pentavalent P-nucleophiles.

Facile synthesis of indoles by K2CO3 catalyzed cyclization reaction of 2-ethynylanilines in water

The cyclization reaction of 2-ethynyl-N-sulfonylanilides proceeded efficiently in water with the presence of a catalytic amount of K2CO3 under transition metal-free condition to give indoles in high yields.The recovery and reusability of the present catalytic system were investigated.

Crystal Structure of 1 －Acetyl －2－［O－methylphenyl） phenyl－ thiophosphonyl］ Hydrazine

The crystals of the title compound C_(15)H_(17)N_2O_2PS were obtained by re crystallizing from ether-methanol solution. It belongs to the orthorhombic system, space group Pbca with a= 9. 255(1) , b= 17.189(8) , c =20. 446(4)A, V=3252.6 (7) A￣3, D_c=1. 31 g/cm￣3,Z= 8, μ(CuKa)=26. 87 cm-1, F(000)=1344. The structure was refined to R=0. 053, R_w=0. 055 for 1299 observed reflections (I≥3σ(I)). In the molecule P atom adopts distorted tetrahedral configuration.The bond (II)distances of P-O, P-N and P-C are 1.605(1) A, 1. 657(1) A 1. 801(1)A,(III)respectively. The X-ray crystallographic analysis demonstrates that there are intramolecular and intermolecular hydrogen bonds in the structure.

Crystal Structure of (1R,4R;1S,4S)2-Amino-3-Cyano-1,4-Diphenyl-2-Cyclopentene-1-ol

The crystal of title compound C18H16N2O was obtained by recrystal-lizing from ethanol solution. It belongs to orthorhombic system, space group Pbca witha=23. 229(2), b=11. 880(3), c=10. 733(3) A, V=2961 (0) A3, Mr=276. 34, Dc=1. 239 g/cm3, Z=8, A(MoKa)=0. 78 cm-1, F(000) =1168. 00. The structurewas refined to R=0. 049 and Rw=0. 046 for 1102 observed reflections (I＞2d(I) ).The bond lengths of C(3) -C(4) and C(3) -N(1) are 1. 349(5) A and 1. 340(6) A,respectively. The bond angles of N (1) -C(3) -C(2), AN (1) -C(3) -C(4), AC(2) -C(3) -C(4) and C(3) -C(4) -C(5) are 121. 1 (4), 128. 4(4), 110. 5(4)and 113. 1 (4), respectively. The dihedral angle between two phenyl rings is 29. 29.

Crystal Structure of Trans-2-Amino-3-Cyano-4-(3',4'-Methylenedioxyphenyl)-1-Phenyl-2-Cyclopentene-r-1-ol

The crystals of the title compound C19H16N2O3 were synthesized by thereaction of 4, 4-dicyano-1-phenyl-3-(3', 4'-methylenedioxyphenyl)-l-butan withlow-valent titanium reagent. It belongs to the orthorhombic system, space group Pea21with a=11. 547(2), b=13. 168(4), c=10. 645(3) A, V=1618. 4(8) A3, Dc=1.315 g/cm3, Z=4, Mr=320.35. A=0. 71069 A, u(MoKa) =0. 90 cm-1, F(000)=672. The structure was refined to R=0. 036, Rw=0. 044 for 962 observed reflections(I＞3(I) ). X-ray analysis reveals that in the five membered ring the C(11) -C(12)bond is longer than normal double C=C bond while the C(11) -N (1) bond is shorterthan normal C(sp)2-N bond.

Integrating Homogeneous and Heterogeneous Catalysis in a Copper Nanocluster with Lewis Acid–Base Sites for Chemical Conversion of CO_(2) and Propargylamine

It remains a significant challenge to develop a catalyst that merges the advantages of homogeneous and heterogeneous catalysis with high reactivity and great recyclability.Herein,an atomically precise Cu_(6)-NH_(2) nanocluster with distorted octahedral Cu_(6) core and NH_(2)-functionalized ligands has been developed as the first homo/heterogeneous catalyst to catalyze the cyclization reaction of propargylic amines with carbon dioxide(CO_(2))under mild conditions.As a homogeneous catalyst,Cu_(6)-NH_(2) shows excellent catalytic activity with high turnover frequency due to highly accessible active sites.The definite coordination geometry and homogeneity nature of active centers make it convenient to investigate the structure–activity relationship at the atomic level through experiments and theory calculations.In addition,the nanocluster exhibits excellent stability,great recrystallizability,and reusability in five catalytic cycles,in which its catalytic performance has no obvious decrease.Moreover,Cu_(6)-NH_(2) incorporates Lewis acid and base sites in metal and ligand,respectively,which can promote catalytic efficiency in a synergistic effect in the absence of any cocatalysts.Importantly,Cu_(6)-NH_(2) can realize direct conversion of CO_(2) in simulated flue gas into oxazolidinones with high efficiency.The metal-ligand cooperative effect and integrated advantages of homogeneous and heterogeneous catalysis would provide new perspectives to achieve advanced metal nanocluster catalysts for CO_(2) conversion.

Recent advances in visible-light photoredox-catalyzed nitrogen radical cyclization

Visible-light photoredox catalysis is a powerful and attractive strategy for organic molecule activation and new reaction design owing to its environmental-friendly characteristics and unique catalytic mechanisms,and has found wide applications in organic synthesis.This catalytic strategy enables controllable generation of diverse nitrogen-centered radicals(NCRs)under mild conditions,providing access to construction of diverse nitrogencontaining compounds.In this review,we critically illustrate the recent advances in the field of visible-light photoredox-catalyzed cyclization of nitrogen-centered radicals,based on the different radical precursors and activation modes.Wherever possible,particular emphasis is also put on working models and synthetic applications.

Synthesis and Cyclization of 8-Formyl-2-（phenoxymethyl）- quinoline-3-carboxylic Acids

A facile synthesis of a series of new quinoline-8-carbaldehyde compounds, namely 8-formyl-2- （phenoxymethyl）quinoline-3-carboxylic acids （4a--4h） and 13-oxo-6,13-dihydro[1]benzoxepino[3,4-b]quinoline- 8-carbaldehyde （5a--5g） is described, involving the one-pot synthesis reaction of ethyl 2-（chloromethyl）-8- formylquinoline-3-carboxylate （3） with substituted phenols followed by the intramolecular cyclization reaction via the treatment with polyphosphoric acid （PPA）. Quinoline-8-carbaldehydes 4a--4h and 5a--5g are novel and their structures were supported by IR, IH NMR, 13C NMR, MS and elemental analysis.

Facile synthesis of isoindoline-l,3-diones by palladium-catalyzed carbonylative cyclization of o-bromobenzoic acid and primary amines

A facile method for the carbonylative cycliza- tion of o-bromobenzoic acid with primary amine using Pd（OAC）2 as a metal precursor and 1, l′-bis（diphenylpho- sphino）ferrocene （dppf） as a ligand has been developed. The effect of various reaction parameters such as ligand, solvent, base, time and temperature on this cyclization was studied. The optimized protocol was used for a wide variety of substituted aryl amines with different steric and electronic properties, affording the corresponding isoindoline-l,3-diones in good to excellent yields under atmospheric pressure of carbon monoxide at 100℃ within 10h using 1,4-diazabicyclo[2.2.2]octane （DABCO） as a base. The reaction system finds attractive alternative to the conventional multistep synthetic process and thus repre- sents an effective utilization of carbonylative protocol for synthesis of valuable chemicals.

Iron-catalyzed synthesis of polycyclic-fused azo[l,2-a]indolones via an S_NAr/acylation cascade reactions

An efficient method has been developed for the cascade synthesis of azo[1,2-a]indolones from azoles and2-fluoroaldehydes based on an iron-catalyzed SNAr and a direct acylation reaction.A number of azo[1,2-a]indolones containing different azole rings and substituents were obtained in good yields.

Gold-catalyzed intermolecular reaction of ynamides with 3-indolyl azides via an unexpected 1,2-alkyl migration

A gold-catalyzed intermolecular reaction of ynamides with 3-indolyl azides via the presumable α-imino gold carbenes has been developed, providing an alternative and efficient way for the synthesis of valuable 3-amino-β-carbolines in generally good to excellent yields. Importantly, this new protocol involves an unexpected 1,2-alkyl migration pathway.

Synthesis of trifluoromethyl-/cyclopropyl-substituted 2-isoxazolines by DBU-promoted domino reaction

NTrifluoromethyl and cyclopropyl substituted 2-isoxazolines were synthesized via a DBU-promoted domino reaction of β-trifluoromethyl-/β-cyclopropyl-substituted enones with hydroxylamine. The domino reaction consists of a Michael addition and the followed cyclization. A wide range of 3-substituted 5-cyclopropyl-5-trifluoromethyl-2-isoxazolines were obtained in good to excellent yields under mild reaction conditions. The method could also apply to other trifluoromethyl-substituted enones.

I2/K2CO3-promoted ring-opening/cyclization/rearrangement/aromatization sequence：A powerful strategy for the synthesis of polysubstituted furans

An efficient and straightforward synthetic method has been developed for the preparation of 4-cyanofuran-3-carboxylate derivatives via iodine/potassium carbonate-promoted ring-opening/cyclization/rearrangement domino reaction of 1-cyanocyclopropane-1-carboxylates,which are a wide range of structurally interesting and pharmacologically significant compounds.

A facile method for building fused quinoxaline-quinolinones via an acidless post-Ugi cascade reaction

A series of quinolino[3,4-b]quinoxalin-6（5H）-ones have been synthesized using an Ugi/deprotection/cyclization（UDC） strategy, followed by a nucleophilic aromatic substitution reaction. This facile microwave-assisted method provided good yields and could potentially be used for the construction of a diverse library of quinolino[3,4-b]quinoxalin-6（5H）-ones for high-throughput screening in medicinal chemistry.

Synthesis of cycloparaphenylene under spatial nanoconfinement

Suzuki coupling reactions between symmetrical monomers were conducted in various mesoporous silica nanoreactors grafted with palladium catalysts,enabling the selective formation of[12]cycloparaphenylene precursor with separate yield up to 25%in one-pot reactions,much higher than that in homogeneous reaction.The spatial nanoconfinement of the nanoreactors promotes the macrocyclization while limits the concomitant linear oligomer formation,offering more possibilities for the synthesis of macrocycles from symmetrical monomers in one-pot reaction.