Asymmetric photocatalysis over robust covalent organic frameworks with tetrahydroquinoline linkage

The asymmetric photocatalytic organic synthesis(APOS)process is a sustainable and environmentally benign method for the production of optically active chemicals with sunlight as an energy source.However,it still lacks efficient semiconductors with tunable band structures and has a low recycling stability.Herein,we report the synthesis of tetrahydroquinoline-linked covalent organic frameworks(QH-COFs)with irreversible tetrahydroquinoline linkage as efficient semiconductors for the visible-light-driven asymmetricα-alkylation of aldehydes by merging with a chiral secondary amine.Up to 94%ee was obtained over QH-COFs,and the activity of QH-COFs was significantly higher than those of inorganic semiconductors(e.g.,Ti O2,Bi VO4,and WO3)under similar conditions,which is mainly attributed to their narrow band gap and suitable band edge.As far as we know,QH-COFs are the most active semiconductors for asymmetricα-alkylation of aldehydes ever reported.The QH-COFs were prepared via a one-pot Povarov cascade imine formation and cycloaddition reaction using Sc(OTf)3/Yb(OTf)3 as Lewis acid catalysts.Attributed to the tetrahydroquinoline linkage,QH-COFs showed extremely high recycling stability,which made practicals application possible.This work not only opens up a new avenue for asymmetric photocatalysis but also provides an efficient and general method for the construction of robust COFs.

Imino Diels-Alder reactions:One-pot synthesis of tetrahydroquinolines

An efficient synthesis of tetrahydroquinoline derivatives is reported via three component coupling reactions of aldehydes and anilines with various dienophiles in the presence of a catalytic amount of perchloric acid adsorbed on silica gel（HClO;-SiO;） under mild reaction conditions.

Zirconyl Chloride Promoted Highly Efficient Domino Synthesis of New 1, 2, 3, 4-Tetrahydroquinoline Derivatives in Water

The tetrahydroquinoline moiety is a structural feature of many natural products. By using a domino reaction of aromatic amines and cyclic enol ethers catalyzed by zirconyl chloride in water, various tetrahydroquinoline derivatives were synthesized efficiently. Most cyclized products showed cis selectivity. The cis selectivity was tentatively rationalized due to chelation control in water.

Three-component one-pot synthesis of 1,2,3,4-tetrahydroquinoline derivatives in hexafluoroisopropanol

The one-pot aza-Diels-Alder reaction of substituted aromatic amines, ethyl glyoxylate and benzyl vinylcarbamate or N- benzyloxycarbonyl 2-pyrroline was conducted in hexafluoroisopropanol, providing the desired 1,2,3,4-tetrahydroquinline derivatives in moderate yields.

Remote stereocontrol in the(4+2)cycloadditions of 1,7-zwitterions:Asymmetric synthesis of multifunctionalized tetrahydroquinoline derivatives

The scope of stereochemistry recognition usually occurs near the chiral scaffold of a ligand or catalyst.Remote stereocontrol,which can surpass the limits of stereorecognition of remote prochiral centers,has long been a challenging object of great interest in asymmetric catalysis.The current work realized the remote stereocontrol of 1,7-zwitterion intermediates formed from Huang's o-amino aryl MBH carbonates.With simple and easily accessibleβ-ICD as the bifunctional catalyst,multifunctionalized tetrahydroquinoline derivatives could be synthesized via(4+2)cycloadditions with excellent enantioselectivity and diastereoselectivity under mild conditions.The strategy possesses broad substrate scope,and three types of electron-deficient enones are successfully applied.Mechanistic studies disclosed the Lewis base-catalyzed reaction pathway,and H-bonding between the catalyst and enones is crucial for long-range stereocontrol.Scale-up reaction and transformations of the tetrahydroquinoline products demonstrated the potential of this strategy.

Rapid assembly of 1,3-indanedione-based spirocyclic tetrahydroquinolines for inducing human lung cancer cell apoptosis

The rapid collection of a library of biologically relevant molecules is essential in new drug discovery.Here we show a variety of bioactive 1,3-indanedione-based spirocyclic tetrahydroquinolines that have been concisely and efficiently constructed under the guidance of biology-oriented synthesis(BIOS).Using Pd(PPh_(3))_(4) as a catalyst,various 2-arylidene-1,3-indanediones can react with vinyl benzoxazinanones under the mild condition to afford a new class of spirocyclic tetrahydroquinolines in moderate to excellent yields(45%-99%)with high stereocontrol(>95:5 diastereoselectivity).Their structures were unambiguously confirmed by X-ray single crystal analysis.The biological evaluation revealed that two of the 1,3-indanedione-based spirocyclic tetrahydroquinolines show remarkable apoptosis-inducing activities over A549 human lung cancer cells,exceeding that of cisplatin.The antitur activities were triggered by reactive oxygen species,commonly overproduced in cancer cells.The clinical demand for antitumor chemotherapy for lung cancer has encouraged an all-out search for analogues with lower toxcity,improved therapeutic index and increased activity.

Imino Diels-Alder Reaction Catalyzed by Iodine： Efficient Synthesis of Tetrahydroquinolines

Iodine was found to be an efficient catalyst for the imino Diels-Alder reaction of N-arylimine with enol ethers to provide tetrahydroquinolines in good yields. The influence of the loading of iodine, reaction solvent, the structure of imine and enol ethers was studied. One pot synthesis of tetrahydroquinolines from aldehyde, aniline and enol ethers catalyzed by iodine was also applicable and provided tetrahydroquinolines in comparable yields. Mild reaction conditions, facile experimental procedure, low price of iodine and good yield of products render this new method attractive for practical synthesis of many tetrahydroquinoline derivatives.

Porphyrin covalent organic framework for photocatalytic synthesis of tetrahydroquinolines

A metal-free porphyrin covalent organic framework was employed as the heterogeneous photocatalyst for the synthesis of tetrahydroquinolines under aerobic conditions.With visible light irradiation of a catalytic amount of H_(2)P-Bph-COF at room temperature,various substituted N,N-dimethylanilines and N-aryl maleimides were transformed to tetrahydroquinoline derivatives in moderate to good yields.This was the first example of the synthesis of tetrahydroquinolines via the photocatalytic aerobic annulation reaction employing the metal-free COF as the heterogeneous photocatalyst.

One-Pot Stereoselective Synthesis of Different Fused Multicyclic Iminosugars Based on the Iminium-lon Intermediate

Different novel fused multicyclic iminosugars were synthesized from D-ribose tosylate,aniline and vinyl ethyl ether by one-pot three-component stereoselective[4+2]reaction at different temperatures.The iminium-ion is the key intermediate for the reaction.As a result,several complex fused iminosugars 3a were obtained by aza-Diels-Alder mechanism at 60℃,while a series of aza-C-glycosides 5a were prepared by Mannich reaction at room temperature accompanied by another tetrahydroquinoline-fused iminosugars 4a(tricyclic derivatives)through aza-Diels-Alder cycloaddition.This strategy will help to construct structurally diverse and bioactive iminosugar analogues.

Synthesis of tetrahydrofuro[3,2-b]quinolin-2(3H)-one derivatives from 2-aminobenzaldehydes and α-angelica lactone via a tandem Aldol/Michael addition

An efficient synthesis of tetrahydrofuro[3,2-b]quinolin-2（3H）-ones from α-angelica lactone and 2-aminobenzaldehydes via a tandem Aldol-Michael addition is described. The reactions were carried out using DBU as the base in i-Pr OH at 0 ℃, affording tetrahydrofuro[3,2-b]quinolin-2（3H）-ones in moderate to good yields.

Kinetic Resolution of 2-Substituted 1,2-Dihydroquinolines by Rhodium-Catalyzed Asymmetric Hydroarylation

A highly efficient kinetic resolution of racemic 2-substituted 1,2-dihydroquinolines via Rh-catalyzed asymmetric hydroarylation has been described for the first time.A variety of arylboronic acids coupled with 2-substituted 1,2-dihydroquinolines under mild reaction condition.The transformations into the enantio-enriched 2,3-diaryl-tetrahydroquinolines as well as the recovered chiral 2-aryl-dihydroquinolines were obtained with high yields and excellent enantioselectivities(86%-99% ee,s factor up to 1057).

One Pot Synthesis of Medicinally Important cis-2.Methyl-4-am i no s u bstituted-1,2,3,4-tetrahyd roq u i nolines

A simple synthesis of medicinally important cis-2-methyl-4-azapan-2-one-1,2,3,4-tetrahydroquinolines/cis-9- （2-methyl-l,2,3,4-tetrahydroquinolin-4-yl）-9H-carbazole was reported. Multicomponent one pot synthesis with ani- lines and N-vinylcaprolactam/N-vinyl carbazole via imino Diels-Alder reaction by using antimony trichloride as catalyst and acetonitrile as solvent was employed. NMR technique （2D） was used to study the regio- and stereo- chemistry of newly synthesized compounds. The cis diastereo-selectivity of the products was predicted by COSY and NOESY studies.