448922-61-0Relevant academic research and scientific papers
Stereocontrol in Diels-Alder cycloaddition to unsaturated sugars: Reactivities of acyclic seven-carbon trans dienophiles derived from aldopentoses
Horton,Koh
, p. 249 - 260 (1993)
Acyclic trans-2,3-unsaturated aldoheptonate derivatives (1-9) obtained from D-aldopentoses by Wittig chain-extension served as dienophiles for a detailed comparative study of their asymmetric Diels-Alder cycloaddition with cyclopentadiene. Cycloaddition under uncatalyzed thermal conditions gave mixtures of the four possible stereoisomeric norbornene adducts. The endo:exo ratios and the diastereofacial selectivities in the formation of the adducts were determined by NMR spectroscopy and by chemical transformations. The quantitative distribution of adducts as a function of stereochemistry of the dienophile is discussed. Acyclic trans-2,3-unsaturated aldoheptonate derivatives (1-9) obtained from D-aldopentoses by Wittig chain-extension served as dienophiles for a detailed comparative study of their asymmetric Diels-Alder cycloaddition with cyclopentadiene. Cycloaddition under uncatalyzed thermal conditions gave mixtures of the four possible stereoisomeric norbornene adducts. The endo:exo ratios and the diastereofacial selectivities in the formation of the adducts were determined by NMR spectroscopy and by chemical transformations. The quantitative distribution of adducts as a function of stereochemistry of the dienophile is discussed.
Influence of solvent polarity on the stereoselectivity of the uncatalyzed [4 + 2] cycloaddition of cyclopentadiene to an N,N′-fumaroyl bis-(six-membered ring [(2R)-10a-homobornane-10a,2-sultam])
Piatek, Anna,Chapuis, Christian,Jurczak, Janusz
, p. 700 - 708 (2003)
A new six-membered ring (2R)-bomane-10a,2-sultam was tested as chiral auxiliary for the [4 + 2] cycloaddition of cyclopentadiene to the bis-fumaroyl derivative (-)-lf and shows under chelating conditions similar complete selectivity to Oppolzer's sultam. Inversion of the π-face selectivity is nevertheless observed under uncatalyzed conditions under the influence of solvent polarity, varying from 82% de for the (2R,3R) cycloadduct 2f in trifluoroethanol to 70% de in favour of the (2S,3S) diastereoisomer in hexane as solvent. A predictive linear correlation is observed between the stereoselectivity and the solvent parameters according to the Abboud-Abraham-Kamlet-Taft model. PM3 calculations allowed a rationalization of these results based on the transition-state dipole moment. Illustrated by an x-ray analysis of cycloadduct (2S,3S)-2f, the main structural differences and influences in terms of steric and stereoelectronic factors are discussed by comparison of the five- versus six-membered ring homologues. Copyright
A Synthetic Strategy for the Construction of a Novel Series of Rigid Supramolecular Triads
Lawson, James M.,Paddon-Row, Michael N.
, p. 1641 - 1643 (1993)
A method is described for constructing totally rigid triad (trichromophoric) supramolecular systems, D2-B1-D1-B2-A, in which the chromophores D2 (dimethylaniline), D1 (dimethoxynaphthalene), and A (dicyanovinyl) are fused to bridges, B1 and B2, consisting of linearly fused norbornyl and bicyclohexanyl units.
Stereo- A nd regioselective synthesis of molecular baskets
Gunther, Michael J.,Pavlovi?, Radoslav Z.,Fernandez, Joseph P.,Zhiquan, Lei,Gallucci, Judith,Hadad, Christopher M.,Badji?, Jovica D.
, p. 4392 - 4401 (2019)
We describe a stereoselective method for obtaining multigram quantities of molecular basket 1syn in overall 11% yield, using inexpensive cyclopentadiene and diethyl fumarate as starting materials. First, an asymmetric synthesis of enantioenriched bromo(trimethylstannyl)alkene (-)-8 was accomplished by the stereoselective bromination of dibromonorbornene (+)-4 guided by anchimeric assistance and subsequent syn-exo-elimination of tetrabromonorbornane (-)-5a as the key steps. Subsequent Cu(I)-catalyzed cyclotrimerization of (-)-8 was optimized to give 1syn/anti in 85% yield and 1:1 ratio of diastereomers. Importantly, the results of our mechanistic experiments were in line with the cyclotrimerization occurring in a chain-type fashion with racemization of a Cu(I) homochiral dimeric intermediate, reducing the stereoselectivity of the transformation. Enabled by more facile access to molecular baskets of type 1syn, a range of recognition studies can now be completed for producing novel supramolecular catalysts, organophosphorus scavengers, and nanostructured materials.
Baeyer-Villiger oxidation of bridged endo-tricyclic ketones with engineered Escherichia coli expressing monooxygenases of bacterial origin
Mihovilovic, Marko D.,Snajdrova, Radka,Winninger, Alexander,Rudroff, Florian
, p. 2751 - 2754 (2005)
Whole-cell biotransformations using engineered strains of Escherichia coli expressing cyclopentanone (CPMO) and cyclohexanone monooxygenases (CHMO) of various bacterial origins have been tested for substrate acceptance on tricyclic ketones. Based on the s
Mechanistic and Kinetic Studies of the Ring Opening Metathesis Polymerization of Norbornenyl Monomers by a Grubbs Third Generation Catalyst
Hyatt, Michael G.,Walsh, Dylan J.,Lord, Richard L.,Andino Martinez, José G.,Guironnet, Damien
, p. 17918 - 17925 (2019)
The mechanism of ring-opening metathesis polymerization (ROMP) for a set of functionalized norbornenyl monomers initiated by a Grubbs third generation precatalyst [(H2IMes)(pyr)2(Cl)2Ru═CHPh] was investigated. Through a series of 12C/13C and 1H/2H kinetic isotope effect studies, the rate-determining step for the polymerization was determined to be the formation of the metallacyclobutane ring. This experimental result was further validated through DFT calculations showing that the highest energy transition state is metallacyclobutane formation. The effect of monomer stereochemistry (exo vs endo) of two types of ester substituted monomers was also investigated. Kinetic and spectroscopic evidence supporting the formation of a six-membered chelate through coordination of the proximal polymer ester to the Ru center is presented. This chelation and its impact on the rate of polymerization are shown to vary based on the monomer employed and its stereochemistry. The combination of this knowledge led to the derivation of a generic rate law describing the rate of polymerization of norbornene monomers initiated by a Grubbs third generation catalyst.
Synthesis and [4 + 2] cycloaddition of (2R,2′R)-N, N′fumaroylbis[fenchane-8,2-sultam] (=(2E)-1,4-bis[(3aS,6S,7aR)-1,4,5,6,7, 7a-hexahydro-7,7-dimethyl-2,2-dioxido-3H-3a,6-methano-2,1-benzothiazol-1-yl] but-2-ene-1,4-dione) to cyclopentadiene
Piatek, Anna M.,Chojnacka, Agnieszka,Chapuis, Christian,Jurczak, Janusz
, p. 2441 - 2453 (2005)
The now corrected X-ray structure of (2R)-bornane-10,2-sultam ((-)-1a), as well as that of its already published N-crotonoyl derivative (-)-1d, were compared with those of the newly synthesized (2R)-fenchane-8,2-sultam ((+)-5a), as well as its N-crotonoyl
Synthesis of Asymmetrically-substituted Cyclopentane Derivatives from Acyclic Sugars
Horton, Derek,Machinami, Tomoya
, p. 88 - 90 (1981)
Diels-Alder addition of cyclopentadiene and trans-α,β-unsaturated sugar derivatives proceeds with high steric control to afford crystalline, optically pure norbornene derivatives that may be transformed into tetra-C-substituted cyclopentane derivatives of defined stereochemistry at all four centres; the products are of interest in synthesis of prostaglandin analogues.
Stereoselectivity in the cycloaddition of cyclopentadiene to N-fumaroyl-[2R,S(R)]-bornane-10,2-sulfinamide monomethyl ester
Chapuis, Christian,Kawecki, Robert,Urbanczyk-Lipkowska, Zofia
, p. 579 - 588 (2001)
The cyclic [2R,S(R)]-bornane-10,2-sulfinamide (-)-2b, an analogue of Oppolzer's camphor-derived sultam (-)-2a, was synthesized by reduction of the known N-alkylidenesulfinamide (+)-1b with NaBH4. The uncatalyzed [4 + 2] cycloaddition of cyclopentadiene to the methyl ester (-)-3b of the N-fumaroylsulfinamide, obtained from (-)-2b, proceeds with lower endo and π-facial selectivity as compared to dienophiles (-)-3a, c. In contrast to these latter, the diastereoselectivity is reversed either in apolar CCl4 or in the presence of TiCl4. This inversion is explained by a competitive C(α)-si addition on the reactive anti-s-trans conformer.
Selective Polymerization Catalysis from Monomer Mixtures: Using a Commercial Cr-Salen Catalyst To Access ABA Block Polyesters
St??er, Tim,Williams, Charlotte K.
, p. 6337 - 6341 (2018)
ABA triblock polyesters are synthesized using a commercially available chromium salen catalyst, in one pot, from monomer mixtures comprising epoxide, anhydride and lactone. The catalysis is highly selective and applies a single catalyst in two distinct pathways. It occurs first by epoxide/anhydride ring-opening copolymerization and subsequently by lactone ring-opening polymerization. It is used to produce various new ABA polyester polyols; these polyols can undergo post-functionalization and chain-extension reactions. The ability to use a commercial catalyst and switchable catalysis with monomer mixtures is expected to facilitate future explorations of new classes of block polymers.
