Cyclization Of Enynes Research Articles

Copper‐Catalyzed Trifluoromethylation–Cyclization of Enynes: Highly Regioselective Construction of Trifluoromethylated Carbocycles and Heterocycles

Regioselective trifluoromethylation-cyclization: A method for copper-catalyzed trifluoromethylation-cyclization of simple enynes using the CC triple bond as a nucleophile is reported for the first time. The reaction proceeds efficiently in a highly regioselective manner to give various 5- or 6-exo-dig carbocycles and heterocycles in moderate to high yields.

ChemInform Abstract: anti‐Carbocyanative Cyclization of Enynes under Nickel Catalysis.

AbstractThe presence of bulky substituents at the C—C triple bond is necessary to achieve highly regio‐ and stereoselective cyclization.

Oxidant-Dependent Chemoselectivity in the Gold-Catalyzed Oxidative Cyclizations of 3,4,6,6-Tetrasubstituted 3,5-Dien-1-ynes

A distinct chemoselectivity in the gold-catalyzed oxidative cyclization of 3,5-dien-1-ynes was observed when 3,5-dichloropyridine N-oxide replaced 8-methylquinoline N-oxide as the oxidant; the resulting cyclopentadienyl aldehydes were obtained in good yields. The altered chemoselectivity is attributed to a prior enyne cyclization in the presence of 3,5-dichloropyridine N-oxides. The use of N-iminopyridium ylide enables a similar iminocyclization reaction to give cyclopentadienyl imines efficiently. Our experimental data support a prior gold-catalyzed cyclization of 3,5-dien-1-ynes to form gold carbene, followed by the oxidation with N-oxide.

ChemInform Abstract: Metal‐Catalyzed Cascade Rearrangements of 3‐Alkynyl Flavone Ethers.

Metal-mediated rearrangements of 3-alkynyl flavone ethers are reported. The overall process involves 5-endo enyne cyclization to a platinum-containing spiro-oxocarbenium intermediate which may be trapped with methanol to produce spirodihydrofurans or further rearranged to afford either allenyl chromanediones or benzofuranones.

Anti Carbocyanative Cyclization of Enynes under Nickel Catalysis

Anti carbocyanative cyclization using 1,6-enynes under nickel catalysis is described. This reaction is triggered by hydronickelation to alkenes followed by carbometalation. Steric repulsion caused by the bulky substituents on alkynes promotes isomerization of the carbon-carbon double bond geometry in an organonickel intermediate to introduce both alkyl and cyano groups in an anti fashion.

Metal-Catalyzed Cascade Rearrangements of 3-Alkynyl Flavone Ethers

Metal-mediated rearrangements of 3-alkynyl flavone ethers are reported. The overall process involves 5-endo enyne cyclization to a platinum-containing spiro-oxocarbenium intermediate which may be trapped with methanol to produce spirodihydrofurans or further rearranged to afford either allenyl chromanediones or benzofuranones.

ChemInform Abstract: Palladium‐Catalyzed Cyclization of Cyclopropyl‐Substituted 1,6‐Enynes to 5.7‐Bicyclic Trienes or Monocyclic Trienes Depending upon the Leaving Group.

AbstractThe cyclization of cyclopropyl‐substituted enynes proceeds in two ways depending on the presence or absence of a leaving group.

Synthesis and Electronic Structure of Bis(imino)pyridine Iron Metallacyclic Intermediates in Iron-Catalyzed Cyclization Reactions

The bis(imino)pyridine iron dinitrogen compound, ((iPr(TB))PDI)Fe(N2)2 ((iPr(TB))PDI = 2,6-(2,6-(i)Pr2-C6H3-N═C-(CH2)3)2(C5H1N)) is an effective precatalyst for the [2π + 2π] cycloaddition of diallyl amines as well as the hydrogenative cyclization of N-tosylated enynes and diynes. Addition of stoichiometric quantities of amino-substituted enyne and diyne substrates to ((iPr(TB))PDI)Fe(N2)2 resulted in isolation of catalytically competent bis(imino)pyridine iron metallacycle intermediates. A combination of magnetochemistry, X-ray diffraction, and Mössbauer spectroscopic and computational studies established S = 1 iron compounds that are best described as intermediate-spin iron(III) (SFe = 3/2) antiferromagnetically coupled to a chelate radical anion (SPDI = 1/2). Catalytically competent bis(imino)pyridine iron diene and metallacycles relevant to the [2π + 2π] cycloaddition were also isolated and structurally characterized. The combined magnetic, structural, spectroscopic, and computational data support an Fe(I)-Fe(III) catalytic cycle where the bis(imino)pyridine chelate remains in its one-electron reduced radical anion form. These studies revise a previous mechanistic proposal involving exclusively ferrous intermediates and highlight the importance of the redox-active bis(imino)pyridine chelate for enabling catalytic cyclization chemistry with iron.

ChemInform Abstract: A New Mode of Cyclization of Enynes. Synthesis of Cycloalkyl Ketones Through a Platinum‐Catalyzed Hydrative Cycloisomerization Reaction.

AbstractThe target compounds are prepared with < 80% d.e.

ChemInform Abstract: Pd‐Catalyzed Borylative Cyclization of 1,7‐Enynes.

AbstractThe cyclization of enynes (I) with dipinacolyl hypodiborate (II) leads to desired cyclic boronate derivatives (III), which can be oxidized to alcohols, e.g. compound (IV).

Nonstatistical Dynamic Effects in the Thermal C2–C6Diels–Alder Cyclization of Enyne–Allenes

The Diels-Alder (DA) reaction channel of the thermal C(2)-C(6) (Schmittel) cyclization of enyne-allenes is studied computationally and experimentally evaluating the influence of temperature on product ratios. Remote substituents at the alkyne terminus influence the mechanism of the C(2)-C(6)/DA cyclization steering it either to a stepwise or a concerted course. Temperature independent product ratios, selectivity of product formation, and computational results obtained at (U)BLYP/6-31G(d) level unveil a mechanism that is strongly controlled by nonstatistical dynamics.

Tandem Cyclizations of 1,6‐Enynes with Arylsulfonyl Chlorides by Using Visible‐Light Photoredox Catalysis

Ray of light: 10a,11-Dihydro-10H-benzo[b]fluorenes were synthesized by a visible-light-catalyzed tandem cyclization of 1,6-enynes with arylsulfonyl chlorides. This method extends the scope of enyne cyclizations and represents a new synthetic application of arylsulfonyl chlorides. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

ChemInform Abstract: Copper‐Catalyzed Oxidative Cyclization of Enynes for the Synthesis of 4‐Carbonylquinolines with O2.

ChemInform Abstract: Copper‐Catalyzed Oxidative Cyclization of Enynes for the Synthesis of 4‐Carbonylquinolines with O₂.

A New Mode of Cyclization of Enynes: Synthesis of Cycloalkyl Ketones through a Platinum‐Catalyzed Hydrative Cycloisomerization Reaction

AbstractA new platinum‐catalyzed cascade reaction that proceeds through an unusual cyclization pathway of enyne derivatives is described. This operationally simple, air‐ and moisture‐tolerant reaction affords cycloalkyl ketone derivatives in a straightforward manner. The reaction can be considered as an unprecedented abnormal platinum‐catalyzed cyclization of enynes. The role of the platinum catalyst promoting at least three different reactions in this auto‐tandem catalytic process should also be remarked. The reaction also includes an unusual site‐selective hydration of a practically symmetrical carbon‐carbon triple bond directed by a hydroxy group. In this work we also describe the first platinum‐catalyzed intramolecular hydroalkylation of an unactivated olefin with a simple dialkyl ketone.

Copper-Catalyzed Oxidative Cyclization of Enynes for the Synthesis of 4-Carbonyl-quinolines with O2

A novel copper-catalyzed oxidative cyclization of enynes and in situ formed enynes leading to 4-carbonyl-quinolines by using dioxygen as an oxygen source has been developed.

ChemInform Abstract: Rh‐Catalyzed Reductive Cyclization of Enynes Using Ethanol as a Source of Hydrogen.

AbstractHydrogen generated from ethanol is used in this reductive cyclization of enynes.

ChemInform Abstract: Ruthenium‐Catalyzed Cyclizations of Enynes via a Ruthenacyclopentene Intermediate: Development of Three Novel Cyclizations Controlled by a Substituent on Alkyne of Enyne

AbstractReview: 61 refs.

Rh‐Catalyzed Reductive Cyclization of Enynes Using Ethanol as a Source of Hydrogen

Rh‐Catalyzed Reductive Cyclization of Enynes Using Ethanol as a Source of Hydrogen

Ruthenium‐catalyzed cyclizations of enynes via a ruthenacyclopentene intermediate: Development of three novel cyclizations controlled by a substituent on alkyne of enyne

Three novel ruthenium-catalyzed cyclizations of enynes were developed. In each cyclization, a ruthenacyclopentene derived from enyne and Cp*RuCl(cod) is a common intermediate. When an enyne having an alkyl, an ester, or a formyl group on an alkyne was reacted with Cp*RuCl(cod) under ethylene gas, ethylene was inserted into the ruthenium-sp(2) carbon bond of ruthenacyclopentene to afford ruthenacycloheptene, and β-hydrogen elimination followed by reductive elimination occurred to give a cyclic compound having a 1,3-diene moiety. When an acyl group was placed on the alkyne, the carbonyl oxygen coordinated to the ruthenium metal of ruthenacyclopentene to produce a ruthenium carbene complex, which reacted with ethylene to give a cyclic compound having a cyclopropane ring on the substituent. On the other hand, when the substituent on the alkyne was pent-4-enyl, insertion of an alkene part into ruthenacyclopentene followed by reductive elimination gave a tricyclic compound by a ruthenium-catalyzed [2+2+2] cyclization of diene and an alkyne.

New Larvicidal Acetogenin from the Red Alga Laurencia papillosa

AbstractA new C15 acetogenin, cyclic enyne (12E)‐cis‐maneonene‐E (1) and (12Z)‐trans‐maneonene‐B (2), together with different secondary metabolites including sesquiterpenoid 2,10‐dibromo‐3‐chloro‐α‐chamigrene (3) and fatty acid aldehydes (4–8) were isolated from the petroleum ether extract of a red alga, identified as Laurencia papillosa, collected from the Saudi Red Sea coast. The L. papillosa crude extract and its active ingredient acetogenin (1) have been evaluated for the ability to control two main economically important pests, the confused flour beetle larvae Tribolium confusum and Culex pipiens mosquito larvae. Compound 1 showed high potential as a natural insecticide against these two pests. In the case of T. confusum larvae, the LD50 values were 0.21 and 0.16% after 6 and 12 days of treatment with crude extract and acetogenin, respectively. On the other hand, the resulting LC50 values of mosquito larvae bioassay were 30.7, 36.9, and 41.8 ppm after 24 h treatment against 2nd, 3rd, and 4th larval instars, respectively. Also, an increase of the insecticidal effects against mosquito larvae was recorded after extending treatment time to 48 h.