Intramolecular Imino Research Articles

Brønsted and Lewis Solid Acid Catalysts in the Valorization of Citronellal

Terpenes are valuable starting materials for the synthesis of molecules that are of interest to the flavor, fragrance, and pharmaceutical industries. However, most processes involve the use of mineral acids or homogeneous Lewis acid catalysts. Here, we report results obtained in the liquid-phase reaction of citronellal with anilines under heterogeneous catalysis conditions to give tricyclic compounds with interesting pharmacological activity. The terpenic aldehyde could be converted into octahydroacridines with a 92% yield through an intramolecular imino Diels–Alder reaction of the imine initially formed in the presence of an acidic clay such as Montmorillonite KSF. Selectivity to the desired product strongly depended on the acid sites distribution, with Brønsted acids favoring selectivity to octahydroacridine and formation of the cis isomer. Pure Lewis acids such as silica–alumina with a very low amount of alumina gave excellent results with electron-rich anilines like toluidine and p-anisidine. This protocol can be applied starting directly from essential oils such as kaffir lime oil, which has a high citronellal content.

Synthesis and antibacterial property of pyrrolopyrano quinolinones and pyrroloquinolines

Synthesis of a series of novel pyrroloquinolinone and pyrroloquinoline derivatives has been accomplished by intramolecular domino Knoevenagel hetero Diels–Alder reaction and intramolecular imino Diels–Alder reaction. These compounds were evaluated for their antibacterial activity against bacterial pathogens using disc diffusion and broth dilution methods. The efficacy of binding of these compounds to gyrase, an enzyme known to play a key role in bacterial replication is examined by studying its supercoiling and relaxation and also its gene expression using PCR method. The results indicated that most of the synthesised compounds exhibited good antibacterial activity against the microorganisms with MIC values of 5mM and could inhibit gyrase effectively leading to cell death.

ChemInform Abstract: Construction of Carbocyclic Arrays Containing Nitrogen via Intramolecular Imino Diels-Alder Reactions in Polar Media. A Comparative Study: 5.0 M Lithium Perchlorate-Diethyl Ether versus Water.

The intramolecular Diels−Alder reaction of iminium ions has been examined in polar media such as 5.0 M lithium perchlorate−diethyl ether and water. Cycloaddition of 3 in 5.0 M lithium perchlorate−diethyl ether containing 10 mol % camphorsulfonic acid proceeds, not by in situ generation of iminium ion 1, but rather via N-(acyloxy)iminium ion 7 which subsequently cyclizes to tricyclic compounds 4 and 5. Direct formation of imines 15 and 30 was realized by reduction of the corresponding lactams (13 and 29, respectively) followed by exposure to 2.0 equiv of tetra-n-butylammonium fluoride. Exposure of the trifluoroacetic acid salt 18 of imine 15 to 5.0 M lithium perchlorate−diethyl ether at ambient temperature gave rise to tricyclic amine 16 in which the diene underwent isomerization prior to [4+2] cycloaddition. In contrast, use of water provided tricyclic amine 19. Similarly, exposure of iminium salt 31 to water afforded tricyclic amine 32. The polar sovent of choice for intramolecular imino Diels−Alder reac...

Intramolecular Imino Diels−Alder Approach to the Synthesis of the Aspidosperma Alkaloid from 3,5-Dibromo-2-pyrone

A new synthetic route to the key framework of aspidosperma alkaloid was devised from the cycloadduct of 3-(2-nitrophenyl)-5-bromo-2-pyrone via intramolecular imino Diels-Alder reaction.

Convenient Preparation of Chiral trans-9,10-Dihydrophenanthrene-9,10-diamine

Chiral trans-9,10-dihydrophenanthrene-9,10-diamine was conveniently prepared from biphenyl-2,2′-dialdehyde using intramolecular imino pinacol coupling and oxidative cleavage of aminoalcohol as key steps.

Intramolecular Imino Diels−Alder Reaction: Progress toward the Synthesis of Uncialamycin

We herein described an intramolecular imino Diels-Alder reaction promoted with BF(3).OEt(2)/DDQ affording substituted quinolines. Using this procedure, we prepared the chiral quinoline moiety of the uncialamycin, a new enediyne natural product.

Synthesis and antibacterial property of quinolines with potent DNA gyrase activity

Synthesis of a series of novel tetrahydroquinoline annulated heterocycles has been accomplished by intramolecular imino and bisimino Diels–Alder reaction. These compounds were evaluated for their antibacterial activity. All the synthetic compounds, exhibited good antibacterial activity against microorganisms of which one of them 7 was found to be as active as the antibiotic ciplofloxacin and is found to have MIC value of 2.5 mg/mL against Escherichia coli.

A novel heterotricyclic assembly through intramolecular imino Diels–Alder reaction: synthesis of pyrrolo[3,4- b]quinolines

The synthesis of a series of hexahydropyrrolo[3,4- b]quinolines has been achieved in excellent yields by the reaction of aldimines derived from aromatic amines and N-prenylated aliphatic aldehydes in acetonitrile with InCl 3 as a catalyst in a short duration of time.

An Efficient, One-Pot Synthesis of Isomeric Ellipticine Derivatives through Intramolecular Imino-Diels−Alder Reaction

New analogues of isomeric ellipticine derivatives fused with biologically important pyrroloindole or chromene moiety have been synthesized by utilizing an intramolecular imino Diels-Alder reaction in a single step.

Indium chloride/silica gel supported synthesis of pyrano/thiopyranoquinolines through intramolecular imino Diels–Alder reaction using microwave irradiation

A facile synthesis of pyrano/thiopyranoquinolines is accomplished in excellent yields through imino Diels–Alder reaction using silica gel impregnated with indium trichloride as catalyst.

Highly diastereoselective synthesis of new indolopyrroloquinolines through intramolecular imino Diels–Alder reactions

A new, efficient and highly diastereoselective one-pot synthesis of cis-fused indolopyrroloquinoline derivatives is described through imino Diels–Alder reaction of substituted anilines or naphthylamines with N-prenylated-2-formyl-3-chloroindoles catalyzed by La(OTf) 3.

A Rapid Intramolecular Imino Diels-Alder Reaction of Aminoanthraquinones with Citronellal or Prenylated Salicylaldehydes: Substituent Effect on Changing the Reaction Pathway from Diels-Alder to Ene-Type Cyclization

The reaction of 1-aminoanthraquinone with citronellal or substituted prenylated salicylaldehyde catalyzed by triphenylphosphonium perchlorate (TPPP) is reported. The nature of the substituents in salicylaldehyde changes the reaction pathway from Diels-Alder to ene-type cyclization.

Indium trichloride catalyzed one-pot synthesis of indolo[2,1- a]pyrrolo[4′,3′:2,3]-7a,8,13,13b-tetrahydroquinolines through intramolecular imino Diels–Alder reactions

An efficient synthesis of tetrahydroquinolines has been achieved by the reaction of aldimines derived from various substituted aromatic amines and indole-2-carbaldehyde containing an internal dienophile using 20 mol % InCl 3 in acetonitrile at room temperature. The reactions are very fast and the products are isolated in good yields and in pure form.

A New Entry to Polycyclic Indole Derivatives via Intramolecular Imino Diels−Alder Reaction: Observation of Unexpected Reaction

A new, efficient, and highly diastereoselective synthesis of polycyclic indole derivatives through intramolecular imino Diels-Alder reaction of aminoanthraquinone with N-prenylated indole-2-carboxaldehydes in the presence of 20 mol % of triphenylphosphonium perchlorate (TPPP) is reported with extremely high cis selectivity in good yield.

NCN Pincer Palladium Complexes: Their Preparation via a Ligand Introduction Route and Their Catalytic Properties.

AbstractFor Abstract see ChemInform Abstract in Full Text.

NCN Pincer Palladium Complexes: Their Preparation via a Ligand Introduction Route and Their Catalytic Properties

A wide range of NCN pincer palladium complexes, [4-tert-butyl-2,6-bis(N-alkylimino)phenyl]chloropalladium (alkyl = n-butyl, benzyl, cyclohexyl, tert-butyl, adamantyl, phenyl, 4-methoxyphenyl), were readily prepared from trans-(4-tert-butyl-2,6-diformylphenyl)chlorobis(triphenylphosphine)palladium via dehydrative introduction of the corresponding alkylimino ligand groups (ligand introduction route) in excellent yields (71-98%). NMR studies on this route for forming pincer complexes revealed the intermediacy of [4-tert-butyl-2,6-bis(N-alkylimino)phenyl]chlorobis(triphenylphosphine)palladium which is in equilibrium with the corresponding NCN pincer complexes via coordination/dissociation of the intramolecular imino groups and triphenylphosphine ligands. A series of chiral NCN pincer complexes bearing pyrroloimidazolone units as the trans-chelating donor groups, [4-tert-butyl-2,6-bis{(3R,7aS)-2-phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-1-on-3-yl}phenyl]chloropalladium, were also prepared from the same precursor via condensation with proline anilides in high yields. The catalytic properties of the NCN imino and the NCN pyrroloimidazolone pincer palladium complexes were examined in the Heck reaction and the asymmetric Michael reaction to demonstrate their high catalytic activity and high enantioselectivity.

InCl3 as an efficient catalyst for intramolecular imino Diels–Alder reactions: Synthesis of tetrahydrochromano quinolines

InCl3 is found to be an efficient catalyst for the Intramolecular Imino Diels-Alder (IMIDA) reaction of aldimines derived from aromatic amines and O-allyl derivatives of salicylaldehydes to afford the corresponding tetrahydrochromano(4,3-b)quinolines in excellent yields under mild conditions and short reaction times.

Inter‐ and Intramolecular Imino Diels—Alder Reactions Catalyzed by Sulfamic Acid: A Mild and Efficient Catalyst for a One‐Pot Synthesis of Tetrahydroquinolines.

The successful use of sulfamic acid as a catalyst in the inter- and intramolecular Inverse Electron Demand Diels-Alder reactions of iminodienes is described. A one-pot synthesis of tetrahydroquinolines was achieved by three component coupling of benzaldehyde and anilines with electron-rich dienophiles such as 2,3-dihydrofuran, dihydropyran and cyclopentadiene catalyzed by sulfamic acid (H 2 NSO 3 H). The intramolecular cycloaddition of imines, derived from O-prenylsalicylaldehyde with anilines catalyzed by sulfamic acid proceeds smoothly and yielded the diastereomeric tetrahydrochromanoquinolines in good yields.

Inter- and Intramolecular Imino Diels-Alder Reactions Catalyzed by Sulfamic Acid: A Mild and Efficient Catalyst for a One-Pot Synthesis of Tetrahydroquinolines

The successful use of sulfamic acid as a catalyst in the inter- and intramolecular Inverse Electron Demand Diels-Alder reactions of iminodienes is described. A one-pot synthesis of tetrahydroquinolines was achieved by three component coupling of benzaldehyde and anilines with electron-rich dienophiles such as 2,3-dihydrofuran, dihydropyran and cyclopentadiene catalyzed by sulfamic acid (H 2 NSO 3 H). The intramolecular cycloaddition of imines, derived from O-prenylsalicylaldehyde with anilines catalyzed by sulfamic acid proceeds smoothly and yielded the diastereomeric tetrahydrochromanoquinolines in good yields.

Construction of Carbocyclic Arrays Containing Nitrogen via Intramolecular Imino Diels−Alder Reactions in Polar Media. A Comparative Study: 5.0 M Lithium Perchlorate−Diethyl Ether versus Water

The intramolecular Diels−Alder reaction of iminium ions has been examined in polar media such as 5.0 M lithium perchlorate−diethyl ether and water. Cycloaddition of 3 in 5.0 M lithium perchlorate−diethyl ether containing 10 mol % camphorsulfonic acid proceeds, not by in situ generation of iminium ion 1, but rather via N-(acyloxy)iminium ion 7 which subsequently cyclizes to tricyclic compounds 4 and 5. Direct formation of imines 15 and 30 was realized by reduction of the corresponding lactams (13 and 29, respectively) followed by exposure to 2.0 equiv of tetra-n-butylammonium fluoride. Exposure of the trifluoroacetic acid salt 18 of imine 15 to 5.0 M lithium perchlorate−diethyl ether at ambient temperature gave rise to tricyclic amine 16 in which the diene underwent isomerization prior to [4+2] cycloaddition. In contrast, use of water provided tricyclic amine 19. Similarly, exposure of iminium salt 31 to water afforded tricyclic amine 32. The polar sovent of choice for intramolecular imino Diels−Alder reac...