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Alkylation

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Haeil Park – 1st expert on this subject based on the ideXlab platform

  • stereoselective protection free asymmetric total synthesis of chamuvarinin a potent anticancer and antitrypanosomal agent substrate controlled construction of the adjacently linked oxatricyclic core by internal Alkylation
    Organic Letters, 2018
    Co-Authors: Mallesham Samala, Thien Nhan Lu, Suresh Mandava, Jungjoong Hwang, Ganganna Bogonda, Haeil Park

    Abstract:

    A stereoselective protection-free asymmetric total synthesis of (+)-chamuvarinin (1), a potent anticancer and antitrypanosomal agent, has been accomplished. The adjacently linked [bis(tetrahydrofuran)]tetrahydropyran (THF–THF–THP) core of this natural product with seven stereogenic centers was constructed in a completely substrate-controlled fashion. The inter-ring stereochemistry (threo,threo,threo) of the oxatricyclic core was established in a stereoselective fashion by a chelation-controlled Keck allylation, whereas the intraring cis or trans relative stereochemistry was controlled by a stereoselective internal Alkylation.

  • Stereoselective Protection-Free Asymmetric Total Synthesis of (+)-Chamuvarinin, a Potent Anticancer and Antitrypanosomal Agent: Substrate-Controlled Construction of the Adjacently Linked Oxatricyclic Core by Internal Alkylation
    Organic Letters, 2018
    Co-Authors: Mallesham Samala, Thien Nhan Lu, Suresh Mandava, Jungjoong Hwang, Ganganna Bogonda, Haeil Park

    Abstract:

    A stereoselective protection-free asymmetric total synthesis of (+)-chamuvarinin (1), a potent anticancer and antitrypanosomal agent, has been accomplished. The adjacently linked [bis(tetrahydrofuran)]tetrahydropyran (THF–THF–THP) core of this natural product with seven stereogenic centers was constructed in a completely substrate-controlled fashion. The inter-ring stereochemistry (threo,threo,threo) of the oxatricyclic core was established in a stereoselective fashion by a chelation-controlled Keck allylation, whereas the intraring cis or trans relative stereochemistry was controlled by a stereoselective internal Alkylation.

Guangbin Dong – 2nd expert on this subject based on the ideXlab platform

  • transition metal catalyzed c h Alkylation using alkenes
    Chemical Reviews, 2017
    Co-Authors: Zhe Dong, Guangbin Dong, Samuel J Thompson, Yan Xu

    Abstract:

    Alkylation reactions represent an important organic transformation to form C–C bonds. In addition to conventional approaches with alkyl halides or sulfonates as alkylating agents, the use of unactivated olefins for Alkylations has become attractive from both cost and sustainability viewpoints. This Review summarizes transition-metal-catalyzed Alkylations of various carbon–hydrogen bonds (addition of C–H bonds across olefins) using regular olefins or 1,3-dienes up to May 2016. According to the mode of activation, the Review is divided into two sections: Alkylation via C–H activation and Alkylation via olefin activation.

Ralph Allen Whitney – 3rd expert on this subject based on the ideXlab platform

  • Synthesis and characterization of ether derivatives of brominated poly(isobutylene‐co‐isoprene)
    Journal of Polymer Science Part A, 2020
    Co-Authors: Sergio A. Guillen-castellanos, J. Scott Parent, Ralph Allen Whitney

    Abstract:

    Variations of the Williamson ether synthesis were employed to prepare a range of new derivatives of brominated poly(isobutylene-co-isoprene) (BIIR). Unambiguous characterization of the polymeric products was accomplished by spectroscopic comparisons to low-molecular-weight analogues derived from brominated 2,2,4,8,8-pentamethyl-4-nonene, which served as a model for the reactive functionality found within BIIR. The substitution of bromide from BIIR occurred at moderate temperatures with stoichiometric amounts of quaternary ammonium phenoxide to yield O-Alkylation products in high yields. Simple mixtures of BIIR, KOH, and aliphatic alcohols generated the desired allylic ethers when heated above 110 °C in the absence of quaternary ammonium salts. Knowledge gained from these small-molecule Alkylations was used to prepare graft copolymers from BIIR and poly(ethylene oxide) through the exploitation of the apparent ability of polyethers to activate potassium alkoxides in nucleophilic substitutions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 983–992, 2006

  • Imidazolium bromide derivatives of poly(isobutylene-co-isoprene): A new class of elastomeric ionomers
    Polymer, 2011
    Co-Authors: J. Scott Parent, Anthony M.j. Porter, Monika R. Kleczek, Ralph Allen Whitney

    Abstract:

    New imidazolium bromide ionomers are prepared by halide displacement from brominated poly(isobutylene-co-isoprene) (BIIR) with a variety of imidazole-based nucleophiles. N-Alkylation of butylimidazole (BuIm) by the allylic halide functionality within BIIR provides stable imidazolium bromide functionality in high yields. Characterization of the resulting thermoformable ionomer by dilute solution viscosity and solid-state rheology shows the effects of ion-pair aggregation on material properties over a range of ionomer composition. Knowledge of BuIm Alkylations is extended to produce thermoset ionomer derivatives through solvent-free reactions of BIIR with 1,1′(1,4-butanediyl)bis(imidazole) and imidazole, whose physical properties stem from both a covalent network and a network of ion-pair aggregates. A novel method of preparing these thermosets is described, wherein a poly(isobutylene-co-isoprene) derivative bearing pendant imidazole functionality is prepared, and heated with BIIR parent material to yield covalent crosslinks comprised of dialkylated imidazole moieties. © 2011 Elsevier Ltd. All rights reserved.