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Transition-Metal Complexes Catalyzed...

Li, Gang.

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Transition-Metal Complexes Catalyzed Hydrogen Atom Transfer: Kinetic Study and Applications to Radical Cyclizations.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Transition-Metal Complexes Catalyzed Hydrogen Atom Transfer: Kinetic Study and Applications to Radical Cyclizations./
作者:	Li, Gang.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2015,
面頁冊數:	178 p.
附註:	Source: Dissertation Abstracts International, Volume: 77-02(E), Section: B.
Contained By:	Dissertation Abstracts International77-02B(E).
標題:	Chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3723660
ISBN:	9781339065229

Transition-Metal Complexes Catalyzed Hydrogen Atom Transfer: Kinetic Study and Applications to Radical Cyclizations.
Li, Gang.

Transition-Metal Complexes Catalyzed Hydrogen Atom Transfer: Kinetic Study and Applications to Radical Cyclizations. - Ann Arbor : ProQuest Dissertations & Theses, 2015 - 178 p.

Source: Dissertation Abstracts International, Volume: 77-02(E), Section: B.

Thesis (Ph.D.)--Columbia University, 2015.

This item is not available from ProQuest Dissertations & Theses.

Radical cyclizations have been proven to be extremely important in organic synthesis. However, their reliance on toxic trialkyltin hydrides has precluded their practical applications in pharmaceutical manufacturing. Many tin hydride substitutes have been suggested but none of them are adequate alternates to the traditional tin reagent.

ISBN: 9781339065229Subjects--Topical Terms:

516420
Chemistry.

Transition-Metal Complexes Catalyzed Hydrogen Atom Transfer: Kinetic Study and Applications to Radical Cyclizations.
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245 1 0 $a Transition-Metal Complexes Catalyzed Hydrogen Atom Transfer: Kinetic Study and Applications to Radical Cyclizations.
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500 $a Source: Dissertation Abstracts International, Volume: 77-02(E), Section: B.
500 $a Adviser: Jack R. Norton.
502 $a Thesis (Ph.D.)--Columbia University, 2015.
506 $a This item is not available from ProQuest Dissertations & Theses.
520 $a Radical cyclizations have been proven to be extremely important in organic synthesis. However, their reliance on toxic trialkyltin hydrides has precluded their practical applications in pharmaceutical manufacturing. Many tin hydride substitutes have been suggested but none of them are adequate alternates to the traditional tin reagent.
520 $a Transition-metal hydrides have been shown to catalyze the hydrogenation and hydroformylation of unsaturated carbon-carbon bonds. Theses reactions begin with a Hydrogen Atom Transfer (HAT) from a metal to an olefin, generating a carbon-centered radical. The cyclization of that radical is an effective route to five- and six-membered rings. The HAT will be fastest if the M--H bond is weak. However, making the reaction catalytic will require that the hydride can be regenerated with H2. HCr(CO)3Cp has proven to be a good catalyst for such cyclizations, but it suffers from air sensitivity. The yield of the cyclization product depends on how the rate of radical cyclization compares with the rates of side reactions (hydrogenation and isomerization), so special substituents on a substrate are best installed to increase the cyclization rate.
520 $a In attempting to improve the efficiency of radical cyclization I have studied the effect of substituents on the target double bond on the rate of cyclization. A single phenyl substituent has proven to stabilize a radical better than two phenyls. This stabilization leads to faster cyclizations and a higher cyclization yield.
520 $a I also have found that Co(dmgBF2)L2 (L = THF, H 2O, MeOH...) under H2 is an effective hydrogen atom donor. I have monitored by NMR the catalysis by the system of the hydrogenation of stable radicals (trityl radical and TEMPO radical) and found the rate-determining step to be the activation of hydrogen gas by CoII. The reactive form of the complex is five-coordinated cobalt complex Co(dmgBF2) 2L.
520 $a The Co/H2 system can also transfer hydrogen atom to C=C bonds, thus initiate radical cyclizations. The resting state of the cobalt is the CoII metalloradical, so a cycloisomerization is obtained. Such a reaction neither loses nor adds any atom and has 100% atom economy.
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650 4 $a Inorganic chemistry. $3 3173556
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