22981-84-6Relevant academic research and scientific papers
Synthesis of a tricyclic lactam via Beckmann rearrangement and ring-rearrangement metathesis as key steps
Kotha, Sambasivarao,Ravikumar, Ongolu,Majhi, Jadab
, p. 1503 - 1508 (2015)
A tricyclic lactam is reported in a four step synthesis sequence via Beckmann rearrangement and ring-rearrangement metathesis as key steps. Here, we used a simple starting material such as dicyclopentadiene.
Silylium ion-catalyzed challenging Diels-Alder reactions: The danger of hidden proton catalysis with strong Lewis acids
Schmidt, Ruth K.,Muether, Kristine,Mueck-Lichtenfeld, Christian,Grimme, Stefan,Oestreich, Martin
supporting information; experimental part, p. 4421 - 4428 (2012/04/23)
The pronounced Lewis acidity of tricoordinate silicon cations brings about unusual reactivity in Lewis acid catalysis. The downside of catalysis with strong Lewis acids is, though, that these do have the potential to mediate the formation of protons by various mechanisms, and the thus released Bronsted acid might even outcompete the Lewis acid as the true catalyst. That is an often ignored point. One way of eliminating a hidden proton-catalyzed pathway is to add a proton scavenger. The low-temperature Diels-Alder reactions catalyzed by our ferrocene-stabilized silicon cation are such a case where the possibility of proton catalysis must be meticulously examined. Addition of the common hindered base 2,6-di-tert-butylpyridine resulted, however, in slow decomposition along with formation of the corresponding pyridinium ion. Quantitative deprotonation of the silicon cation was observed with more basic (Mes)3P to yield the phosphonium ion. A deuterium-labeling experiment verified that the proton is abstracted from the ferrocene backbone. A reasonable mechanism of the proton formation is proposed on the basis of quantum-chemical calculations. This is, admittedly, a particular case but suggests that the use of proton scavengers must be carefully scrutinized, as proton formation might be provoked rather than prevented. Proton-catalyzed Diels-Alder reactions are not well-documented in the literature, and a representative survey employing TfOH is included here. The outcome of these catalyses is compared with our silylium ion-catalyzed Diels-Alder reactions, thereby clearly corroborating that hidden Bronsted acid catalysis is not operating with our Lewis acid. Several simple-looking but challenging Diels-Alder reactions with exceptionally rare dienophile/enophile combinations are reported. Another indication is obtained from the chemoselectivity of the catalyses. The silylium ion-catalyzed Diels-Alder reaction is general with regard to the oxidation level of the α,β-unsaturated dienophile (carbonyl and carboxyl), whereas proton catalysis is limited to carbonyl compounds.
Experimental Diels-Alder reactivities of cycloalkenones and cyclic dienes explained through transition-state distortion energies
Paton, Robert S.,Kim, Seonah,Ross, Audrey G.,Danishefsky, Samuel J.,Houk
supporting information; experimental part, p. 10366 - 10368 (2011/12/04)
Quantum chemical calculations are used to investigate the experimentally measured reactivities of cyclic dienes and cycloalkenones in the Diels-Alder reaction. The interaction energies (red) are nearly constant; differences arise in changes in distortion energies of both dienophile (blue) and diene (green; see picture, Ea=activation energy; values in kcal mol-1). Copyright
Asymmetric synthesis of tetracyclic benzo[a]quinolizidine targets
Allin, Steven M.,Gaskell, Sean N.,Elsegood, Mark R. J.,Martin, William P.
, p. 6448 - 6451 (2008/12/21)
(Chemical Equation Presented) We report a novel, facile, and asymmetric approach for the synthesis of polycyclic benzo[a]quinolizidine targets. In the formation of more functionalized derivatives, we have observed the generation of an iminium ether salt intermediate, formed during an unprecedented retro-Diels-Alder/N-acyliminium cyclization cascade. The iminium ether intermediate was isolated in good yield, characterized by X-ray crystallography, and subsequently applied as a synthetic building block.
Synthesis and evaluation of new chiral diols based on the dicyclopentadiene skeleton
Borsato, Giuseppe,De Lucchi, Ottorino,Fabris, Fabrizio,Lucchini, Vittorio,Frascella, Pietrogiulio,Zambon, Alfonso
, p. 3517 - 3520 (2007/10/03)
The resolution by Lipase PS of rac-5 (from reduction of ketone 6, obtained from dicyclopentadiene with a new environment-friendly synthesis) gives (2S)-5, which was further reduced to the endo (2R)-1a alcohol. The endo (2S)-1b alcohol was obtained from camphor with a multistep synthesis. Pinacol couplings of 3a,b, carried out with Mg/Hg or Corey's general procedure respectively, afforded with high diastereoselectivity the C2 symmetry diols (2R,2′R)-2a and (2S,2′S)-2b, with endo oriented OH functions. The enantiogenic power of the endo alcohol (2R)-1a and (2S)-1b and of the diols (2R,2′R)-2a and (2S,2′S)-2b was tested towards the LiAlH4 reduction of acetophenone. The C2 symmetry appears to play a fundamental role.
Studies in Lewis acid and LiClO4 (or Nafion-H) catalysed ionic Diels- Alder reactions of chiral and achiral olefinic acetals respectively
Kumareswaran,Vankar, Padmar S.,Reddy, M. Venkat Ram,Pitre, Sangeeta V.,Raja, Roy,Vankar, Yashwant D.
, p. 1099 - 1110 (2007/10/03)
Chiral olefinic acetals derived from crotonaldehyde undergo ionic Diels- Alder reaction giving the corresponding cycloadducts in moderate to good diastereoselectivities. A variety of achiral olefinic acetals react with isoprene and cyclopentadiene to form the cycloadducts in good to excellent yields when catalysed by 4M LiClO4 in nitromethane or by Nafion-H in dichloromethane.
Construction of cis-fused bicyclo[n.3.0] systems via Diels-Alder reaction-oxidation sequence
Babu,Sridar
, p. 711 - 712 (2007/10/03)
Diels-Alder reaction of cyclopentadiene with cyclopentenone, cycloheptenone and cyclooctenone shows excellent endo selectivity and all the endo-adducts 2 including the known adduct of cyclohexenone are oxidatively cleaved to produce the bicyclo[n.3.0] systems 3.
Linearly Fused vs Bridged Regioselection in the Intramolecular 1,3-Diyl Trapping Reaction
Masjedizadeh, Mohammad R.,Dannecker-Doering, Ingeborg,Little, R. Daniel
, p. 2742 - 2752 (2007/10/02)
The intramolecular diyl trapping reaction can now be used to obtain synthetically useful quantities of either bridged or linearly fused cycloadducts in a selective manner and by design.Bridged cycloadducts arise by intercepting the triplet diyl, while linearly fused products can be produced from either the singlet or the triplet.When an electron-withdrawing group is attached to the diylophile , the singlet diyl leads selectively to fused cycloadducts.On the other hand , the presence of a large alkyl group attached to the internal carbon of the diylophile affords bridged cycloadducts selectively from cycloaddition with the triplet.Four diazenes, 4-7, differing only in the electronic and steric properties of the substituent located on the internal carbon of the diylophile, were studied.The diyl trapping reactions were conducted using ca. 1 mM solutions of diazene in THF at reflux for periods of 3-4h; cycloadduct yields ranged from 68percent ( beginning with the dimethyl ketal 7) to 98percent ( from keto diazene 4).To determine the origin of the bridged cycloadducts, the effect of oxygen upon the product distribution was examined.The results show that the rate of the intramolecular triplet diyl cycloaddition is slower than the rate of the intermolecular reaction of the triplet with oxygen.The rate of triplet intramolecular cycloaddition can be estimated to be less than 4 x 106 to 4 x 107 s-1.
AN IMPROVED SYNTHESIS OF DESLONGCHAMPS'S DIKETONE BY DIRECT REGIOSELECTIVE FUNCTIONALIZATION OF endo-DICYCLOPENTADIENE
Carceller, Elena,Garcia, M. Lluisa,Moyano, Albert,Serratosa, Felix
, p. 951 - 958 (2007/10/02)
A high yield three-step synthesis of endo-tricyclo2,6>deca-4,8-dione (Deslongchamps's diketone) by a stepwise regioselective oxymercuration of commercial endo-dicyclopentadiene is described.
