34932-07-5Relevant academic research and scientific papers
Diels-Alder reactions of α-vinylidene-γ-butyrolactones
Fotiadu,Archavlis,Buono
, p. 4859 - 4862 (1990)
α-Vinylidene-γ-butyrolactones 2 and 4 are readily prepared via the reaction of ylides 1 or 3 with ketene. Diels-Alder cycloadditions of these compounds with typical dienes are described, addition of 2 to cyclopentadiene giving predominantly the exo stereomer.
Selective Construction of C?C and C=C Bonds by Manganese Catalyzed Coupling of Alcohols with Phosphorus Ylides
Liu, Xin,Werner, Thomas
, p. 1096 - 1104 (2020/12/31)
Herein, we report the manganese catalyzed coupling of alcohols with phosphorus ylides. The selectivity in the coupling of primary alcohols with phosphorus ylides to form carbon-carbon single (C?C) and carbon-carbon double (C=C) bonds can be controlled by the ligands. In the conversion of more challenging secondary alcohols with phosphorus ylides the selectivity towards the formation of C?C vs. C=C bonds can be controlled by the reaction conditions, namely the amount of base. The scope and limitations of the coupling reactions were thoroughly evaluated by the conversion of 21 alcohols and 15 ylides. Notably, compared to existing methods, which are based on precious metal complexes as catalysts, the present catalytic system is based on earth abundant manganese catalysts. The reaction can also be performed in a sequential one-pot reaction generating the phosphorus ylide in situ followed manganese catalyzed C?C and C=C bond formation. Mechanistic studies suggest that the C?C bond was generated via a borrowing hydrogen pathway and the C=C bond formation followed an acceptorless dehydrogenative coupling pathway. (Figure presented.).
Photoenzymatic Generation of Unstabilized Alkyl Radicals: An Asymmetric Reductive Cyclization
Clayman, Phillip D.,Hyster, Todd K.
supporting information, p. 15673 - 15677 (2020/10/18)
Flavin-dependent "ene"-reductases can generate stabilized alkyl radicals when irradiated with visible light; however, they are not known to form unstabilized radicals. Here, we report an enantioselective radical cyclization using alkyl iodides as precursors to unstabilized nucleophilic radicals. Evidence suggests this species is accessed by photoexcitation of a charge-transfer complex that forms between flavin and substrate within the protein active site. Stereoselective delivery of a hydrogen atom from the flavin semiquinone to the prochiral radical formed after cyclization provides high levels of enantioselectivity across a variety of substrates. Overall, this transformation demonstrates that photoenzymatic catalysis can address long-standing selectivity challenges in the radical literature.
Nickel-catalyzed, ligand-free, diastereoselective synthesis of 3-methyleneindan-1-ols
Panchal, Heena,Clarke, Christopher,Bell, Charles,Karad, Somnath Narayan,Lewis, William,Lam, Hon Wai
supporting information, p. 12389 - 12392 (2018/11/20)
Nickel-catalyzed, highly diastereoselective annulations between activated allenes and 2-acetylarylboronic acid or 2-formylarylboronic acids are reported. No ligand for nickel is required, and the reactions proceed efficiently at room temperature to give a broad range of substituted 3-methyleneindan-1-ols. Preliminary results of an enantioselective variant are also described.
A modular and scalable one-pot synthesis of polysubstituted furans
Fournier, Jeremy,Arseniyadis, Stellios,Cossy, Janine
supporting information; experimental part, p. 7562 - 7566 (2012/10/18)
One four all: Allyl dienol carbonates can be readily converted into diversely substituted furans by a one-pot four-step sequence featuring a palladium-catalyzed decarboxylative allylic alkylation, a microwave-mediated Cope rearrangement, a nucleophilic addition, and a dehydration reaction (see scheme). The protocol is operationally simple, highly flexible, and provides di-, tri-, and tetrasubstituted furans starting from readily available materials. Copyright
Stereoselective olefination of N-sulfonyl imines with stabilized phosphonium ylides for the synthesis of electron-deficient alkenes
Fang, Fan,Li, Yuan,Tian, Shi-Kai
supporting information; experimental part, p. 1084 - 1091 (2011/04/15)
An unprecedented protocol has been developed for thestereoselective synthesis of structurally diverse electron-deficient alkenes in moderate to excellent yields from readily accessible N-sulfonyl imines and stabilized phosphonium ylides. Significantly, the olefination reaction of N-sulfonylimines with nitrile-stabilized phosphonium ylides affords an array of α,β-unsaturated nitriles with high Z selectivity, and the reactions with ester-, amide-, and ketone-stabilized phosphonium ylides afford α,β-unsaturated esters, amides, and ketones with high E selectivity, respectively. Spectroscopic analysis of the reaction mixtures and trapping of the intermediates allow plausible mechanisms to be proposed. Initialimine/ylide addition leads to the formation of betaines that cyclize to form 1,2-azaphosphetanes that subsequently eliminate iminophosphoranes to yield alkenes. For the synthesis of electron-deficient 1,2-disubstituted alkenes, the presence of an electron-withdrawing group in the betaine allows rapid interconversion between its two diastereomers through proton transfer. The Z/E selectivity for alkene synthesis is determined by the different rates at which the two betaine diastereomers form the corresponding 1,2-azaphosphetane diastereomers. In contrast, the Z/E selectivity for the synthesis of electron-deficient trisubstituted alkenes originates from the diastereoselective addition of stabilized phosphonium ylides to N-sulfonyl imines.
Efficient synthesis of an A-B-C-tricycle fragment for a structural model of tolyporphin
Hu, Bing C.,Zhou, Wei Y.,Liu, Zu L.,Cai, Chao J.,Xu, Shi C.
scheme or table, p. 89 - 100 (2010/11/18)
An efficient stereocontrolled synthesis of an A-B-C-tricycle fragment 7 for a structural model of tolyporphin 3 is described. All the rings were prepared from readily available starting materials. One of the two key steps is a selective ring-opening reaction of the lactone cycle in bicyclolactam-lactone 17 to cyanopyrrolidone 18, which introduces the chirality into synthetic compounds. The other key step is the combination of A ring with B-C-bicycle via a two-time Eschenmoser sulfide contraction. A-B-C-tricycle fragment 7 allows a new approach toward tolypophin compounds and other uroporphinoids.
An intramolecular cobalt cyclisation for the construction of substituted pyrrolidines
Baldwin, Jack E.,Moloney, Mark G.,Parsons, Andrew F.
, p. 9373 - 9384 (2007/10/02)
Cobalt mediated cyclisations of a radical onto a substituted allylamine can be used to generate highly functionalised pyrrolidines. The facility of the ring closure depends on the nature of substituents on the alkene moeity. Dehydrocobaltation of the init
Synthesis of Chain-Extended and C-6' Functionalized Precursors of the Nucleoside Antibiotic Sinefungin
Lyga, John W.,Secrist, John A.
, p. 1982 - 1988 (2007/10/02)
Precursors of sinefungin were prepared by chain extension of the blocked adenosine 5'-aldehyde 4 through a carbon-carbon bond to C-5'.Bond formation was accomplished with variously functionalized stabilized ylides.Employment of 2-oxo-3-(triphenylphosphora
Synthesis of alkyl substituted α,β unsaturated γ lactones as potential antitumor agents
Howie,Manni,Cassady
, p. 840 - 843 (2007/10/07)
A series of alkyl substituted di and monolactones including (E,E) 3,3 (alkanediylidene)bis[dihydro 2(3H) furanones] and the monolactones was synthesized by reaction of α (triphenylphosphoranylidene) γ butyrolactone with appropriate aldehydes. The reaction of this ylide with formaldehyde gave α methylene γ butyrolactone. These compounds were tested for antitumor activity as part of a study to determine the influence of β substituents and distance between alkylating sites on the antitumor activity of α,β unsaturated lactones. The testing was carried out in standard National Cancer Institute screens and the compounds possessed ED50 values of 16 to 110 μg/ml against cells derived from human carcinoma of the nasopharynx (KB) and were inactive against L1210 lymphoid leukemia in the mouse.
