An Asymmetric Hydrovinylation of 1,4-Substituted Linear 1,3-Dienes

An Asymmetric Hydrovinylation of 1,4-Substituted Linear 1,3-Dienes

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Main Author: Gordon, Jonanthan Paul
Language:English
Published: The Ohio State University / OhioLINK 2018
Subjects:
Chemistry
Hydrovinylation
Catalysis
Cobalt
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=osu1535035303696191
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-osu15350353036961912021-08-03T07:08:18Z An Asymmetric Hydrovinylation of 1,4-Substituted Linear 1,3-Dienes Gordon, Jonanthan Paul Chemistry Hydrovinylation Catalysis Cobalt Even though hydrovinylations (HV) of 1,3-dienes have been extensively studied, a class of substrates that has not received much attention are the 1,4-disubstituted derivatives. The work described in this thesis addresses the gap in this area. A variety of 1,3-dienes were prepared using existing methods starting from an a,b-unsaturated aldehyde. Thus, Wittig reactions provided: (2E,4E)-deca-2,4-diene and (2Z,4E)-deca-2,4-diene, (4E,6E)-dodeca-4,6-diene and (4Z,6E)-dodeca-4,6-diene, (1E,3E)-1-methoxynona-1,3-diene and (1Z,3E)-1-methoxynona-1,3-diene, and (1E,3E)-1- bromonona-1,3-diene and (1Z,3E)-1-bromonona-1,3-diene. The remaining substrates were synthesized from an intermediate alcohol (2E,4E)-hexa-2,4-dien-1-ol obtained via diisobutylaluminum hydride (DIBAL) reduction of commercially available ethyl sorbate. Protection of this alcohol with t-butyldimethylsilyl (TBS) and benzyl (Bn) groups provided substrates which provedviable under modified reaction conditions for cobalt-catalyzed asymmetric HVestablished in our research group. This involves reduction of an (L’~L)CoX2 complex[L’~L = 1, n-bis-diphenylphosphinoalkane, phosphinooxazoline (PHOX)] with Znfollowed by activation by sodium teterakis-1,3-bis-triflurophenylborate (NaBArF) toprepare the active catalyst, and, subsequently adding the diene in the presence ofethylene. An achiral ligand [1,3-bis(diphenylphosphino)propane (dppp)] was usedexplore the feasibility of the catalytic HV and to identify the 4 possible chiral products(corresponding to 1,4-additions at each of the termini) by GC. Interestingly, the substrate functionalized at the C1 position with a halogen [(1E,3E)-1- bromonona-1,3-diene and (1Z,3E)-1-bromonona-1,3-diene] was unreactive. In the case of tert-butyl(((2E,4E)-hexa-2,4-dien-1-yl)oxy)dimethylsilane the reaction required additional optimization. Of the chiral ligands explored phenyl PHOX proved most effective giving enantiomeric excesses (>90%) in several instances even though the regioselectivity needs further improvement. Other chiral ligands explored [((2,2-dimethyl-1,3-dioxolane-4,5-diyl)bis(methylene))bis(diphenylphosphane)] (DIOP) and [((2S,4S)-pentane-2,4-diyl)bis(diphenylphosphane)] (BDPP) effected the reaction only slowly and with only modest yields and selectivities, sometimes with unacceptably high amounts of unwanted byproducts. The use of easily tunable PHOX ligands in these reactions is novel, and holds considerable promise for further development of a broadly applicable reaction. 2018 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1535035303696191 http://rave.ohiolink.edu/etdc/view?acc_num=osu1535035303696191 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection NDLTD
language English
sources NDLTD
topic Chemistry
Hydrovinylation
Catalysis
Cobalt
spellingShingle Chemistry
Hydrovinylation
Catalysis
Cobalt
Gordon, Jonanthan Paul
An Asymmetric Hydrovinylation of 1,4-Substituted Linear 1,3-Dienes
author Gordon, Jonanthan Paul
author_facet Gordon, Jonanthan Paul
author_sort Gordon, Jonanthan Paul
title An Asymmetric Hydrovinylation of 1,4-Substituted Linear 1,3-Dienes
title_short An Asymmetric Hydrovinylation of 1,4-Substituted Linear 1,3-Dienes
title_full An Asymmetric Hydrovinylation of 1,4-Substituted Linear 1,3-Dienes
title_fullStr An Asymmetric Hydrovinylation of 1,4-Substituted Linear 1,3-Dienes
title_full_unstemmed An Asymmetric Hydrovinylation of 1,4-Substituted Linear 1,3-Dienes
title_sort asymmetric hydrovinylation of 1,4-substituted linear 1,3-dienes
publisher The Ohio State University / OhioLINK
publishDate 2018
url http://rave.ohiolink.edu/etdc/view?acc_num=osu1535035303696191
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AT gordonjonanthanpaul asymmetrichydrovinylationof14substitutedlinear13dienes
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