92362-23-7Relevant academic research and scientific papers
Lewis Base Catalyzed, Sulfenium Ion Initiated Enantioselective, Spiroketalization Cascade
Denmark, Scott E.,Hilby, Kimberly M.
, p. 14250 - 14289 (2021/11/12)
A Lewis base catalyzed, enantioselective sulfenocyclization of alkenes to afford [6,6]spiroketals has been developed. The method uses a chiral Lewis base catalyst with an electrophilic sulfur source to generate enantioenriched thiiranium ion with alkenes. Upon formation, the thiiranium ion is subsequently captured in a cascade-type reaction, wherein a ketone oxygen serves as the nucleophile to open the thiiranium ion and an alcohol provides the secondary cyclization to form biorelevant spiroketals. A variety of electron-rich and electron-neutral E-substituted styrenes form the desired spiroketals in good yields with excellent enantio- and diastereoselectivities. Alkyl-substituted and terminal alkenes participate in the cascade reaction, but with a limited scope compared to the styrenyl substrates. This method allows for rapid formation of highly substituted spiroketals in good yield and excellent enantioselectivity.
Heterocycle synthesis based on allylic alcohol transposition using traceless trapping groups
Xie, Youwei,Floreancig, Paul E.
supporting information, p. 4926 - 4929 (2014/05/20)
Allylic alcohols undergo transposition reactions in the presence of Re 2O7 whereby the equilibrium can be dictated by trapping one isomer with a pendent electrophile. Additional ionization can occur when the trapping group is an aldehyde or ketone, thus leading to cyclic oxocarbenium ion formation. Terminating the process through bimolecular nucleophilic addition into the intermediate provides a versatile method for the synthesis of diverse oxygen-containing heterocycles. Understanding the relative rates of the steps in the sequence leads to the design of reactions which create multiple stereocenters with good to excellent levels of control.
FeCl3-catalyzed highly diastereoselective synthesis of substituted piperidines and tetrahydropyrans
Guerinot, Amandine,Serra-Muns, Anna,Gnamm, Christian,Bensoussan, Charlelie,Reymond, Sebastien,Cossy, Janine
supporting information; experimental part, p. 1808 - 1811 (2010/10/03)
The eco-friendly and highly diastereoselective synthesis of substituted cis-2,6-piperidines and cis-2,6-tetrahydropyrans is described. The key step of this method is the iron-catalyzed thermodynamic equilibration of 2-alkenyl 6-substituted piperidines and 2-alkenyl 6-substituted tetrahydropyrans allowing the isolation of enriched mixtures of the most stable cis-isomers.
Synthesis of Spiroacetals using Organoselenium-mediated Cyclisation Reactions. X-Ray Molecular Structure of (2S,8R)-8-Methyl-2-phenyl-1,7-dioxaspiroundecan-4(R)-ol
Doherty, Annette M.,Ley, Steven V.,Lygo, Barry,Williams, David J.
, p. 1371 - 1378 (2007/10/02)
Alkenyl hydroxyketones undergo cyclisation via their hemiacetal form, in the presence of N-phenylselenophthalimide (NPSP) and a Lewis acid, to give the corresponding phenylseleno-substituted spiroacetals.Using this methodology the synthesis of trans- and cis-2-methyl-1,6-dioxaspirononane (1), trans- and cis-2-ethyl-1,6-dioxaspirononane (chalcogran)(2), trans- and cis-2-methyl-1,6-dioxaspirodecane(3), trans-7-methyl-1,6-dioxaspirodecane (4), trans-2-methyl-1,7-dioxaspiroundecane (5), and (2S,8R)-8-methyl-2-phenyl-1,7-dioxaspiroundecane-4-one(6) has been achieved, after reductive removal of selenium using Raney-nickel in diethyl ether.Compound (2) is the principal aggregation pheromone from Pityogenes chalcographus (L), whilst compounds (3) and (4) constitute the pheromone components of the common wasp, Paravespula vulgaris.The structure of the spiroacetal (6) was determined as a result of X-ray crystallography of a later derivative, obtained by sodium borohydride reduction of (6).
