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Asymmetric synthesis from solid state photochemical asymmetric induction to catalytic asymmetric hydrogenation Liu, Zhaoqing
Abstract
A number of phosphine oxides were synthesized via different routes. Grignard displacement of menthyl phosphinates afforded different enantiopure monophosphine oxides. By coupling the monophosphine oxides, bisphosphine dioxides I were prepared. 1,2-Ethynediylbis(diphenylphosphine oxide) was reacted with anthracene and its derivatives to give Diels-Alder adducts ethenoanthracenes, and two of them were further reduced to ethanoanthracenes by magnesium in methanol. A new enantiopure bisphosphine ligand, anthraphos (II), was prepared. Dibenzobarrelene derivatives III form well defined crystalline complexes with triphenylphosphine oxide as well as with bisphosphine dioxides I. Irradiation of the complexes in the solid state led, via the di-π-methane rearrangement, to pairs of regioisomeric dibenzosemibullvalene photoproducts. The ratio in which these products are formed was found to vary markedly with the structure of the phosphine oxide. Low to moderate photoproduct enantioselectivities were observed in the complexes with enantiopure diphosphine dioxides. Five of the complexes studied had their crystal and molecular structures determined by X-ray crystallography. Correlations between the photochemical behavior of the complexes in the solid state and their crystal structures are discussed. The new host IV forms crystalline inclusion complexes with a wide variety of aliphatic solvent molecules. The molecular and crystal structures of these complexes were analyzed by X-ray crystallography. The crystal structures show that the complexes with ethanol, 1-propanol and 2-propanol have the chiral space group P2,2,2], where the absolute configuration of IV was assigned. The inclusion complexes can undergo the di- π-methane rearrangement to result in dibenzosemibullvalene derivative product V in solution and the solid state. In the case of the complexes with ethanol, 1-propanol and 2-propanol, the solid state photoreaction gave product V in more than 90% e.e.; this reaction was used for the asymmetric synthesis of bisphosphine ligand VI. The absolute configuration of dibenzosemibullvalene V was also determined. By correlating the absolute configuration of reactant IV with that of its photoproduct V, the key structural features responsible for the enantiospecific solid state photorearrangement were elucidated. Other ethenoanthracene phosphine oxide derivatives were also examined for inclusion complex formation as well as for solid state photochemical asymmetric induction. 9,10-Dihydro-9,10-ethenoanthracene-11-(diphenylphosphine oxide)-12-carboxylic acid and its ethyl ester were photolysed in different media including the solid state, and two regioisomers were obtained in each case. The medium-dependent regioselectivity was considered to result from the conformations in which the phosphinoyl group could be free or hydrogen bonded. Two different mechanisms were applied to rationalize the regioselectivity. The reactivity was correlated with the crystal structures of the starting material. An active asymmetric catalyst, [Rh(COD)(R,R-anthraphos)]BF₄, was prepared from enantiopure anthraphos (II). The molecular and crystal structure of this catalyst was analyzed by X-ray crystallography and compared with the known structures of chiraphos and norphos. Use of [Rh(COD)(R,R-anthraphos)]BF₄ to hydrogenate (Z)-α-acetamidocinnamic acid gave (S)-(+)-N-acetylphenylalanine in 90% e.e. Bisphosphine VI was also used for the same purpose, but gave lower enantioselectivity. Different ruthenium-anthraphos complexes were also synthesized by ligand exchange reactions in an attempt to use them as asymmetric catalysts in the hydrogenation of C=C, C=O and C=N bonds. [chemical compound diagrams]
Item Metadata
Title |
Asymmetric synthesis from solid state photochemical asymmetric induction to catalytic asymmetric hydrogenation
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1995
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Description |
A number of phosphine oxides were synthesized via different routes. Grignard
displacement of menthyl phosphinates afforded different enantiopure monophosphine
oxides. By coupling the monophosphine oxides, bisphosphine dioxides I were prepared.
1,2-Ethynediylbis(diphenylphosphine oxide) was reacted with anthracene and its
derivatives to give Diels-Alder adducts ethenoanthracenes, and two of them were further
reduced to ethanoanthracenes by magnesium in methanol. A new enantiopure
bisphosphine ligand, anthraphos (II), was prepared.
Dibenzobarrelene derivatives III form well defined crystalline complexes with
triphenylphosphine oxide as well as with bisphosphine dioxides I. Irradiation of the
complexes in the solid state led, via the di-π-methane rearrangement, to pairs of
regioisomeric dibenzosemibullvalene photoproducts. The ratio in which these products
are formed was found to vary markedly with the structure of the phosphine oxide. Low
to moderate photoproduct enantioselectivities were observed in the complexes with
enantiopure diphosphine dioxides. Five of the complexes studied had their crystal and
molecular structures determined by X-ray crystallography. Correlations between the
photochemical behavior of the complexes in the solid state and their crystal structures are
discussed.
The new host IV forms crystalline inclusion complexes with a wide variety of
aliphatic solvent molecules. The molecular and crystal structures of these complexes
were analyzed by X-ray crystallography. The crystal structures show that the complexes
with ethanol, 1-propanol and 2-propanol have the chiral space group P2,2,2], where the
absolute configuration of IV was assigned. The inclusion complexes can undergo the di-
π-methane rearrangement to result in dibenzosemibullvalene derivative product V in
solution and the solid state. In the case of the complexes with ethanol, 1-propanol and
2-propanol, the solid state photoreaction gave product V in more than 90% e.e.; this
reaction was used for the asymmetric synthesis of bisphosphine ligand VI. The absolute
configuration of dibenzosemibullvalene V was also determined. By correlating the
absolute configuration of reactant IV with that of its photoproduct V, the key structural
features responsible for the enantiospecific solid state photorearrangement were
elucidated. Other ethenoanthracene phosphine oxide derivatives were also examined for
inclusion complex formation as well as for solid state photochemical asymmetric
induction.
9,10-Dihydro-9,10-ethenoanthracene-11-(diphenylphosphine oxide)-12-carboxylic
acid and its ethyl ester were photolysed in different media including the solid state, and
two regioisomers were obtained in each case. The medium-dependent regioselectivity
was considered to result from the conformations in which the phosphinoyl group could
be free or hydrogen bonded. Two different mechanisms were applied to rationalize the
regioselectivity. The reactivity was correlated with the crystal structures of the starting
material.
An active asymmetric catalyst, [Rh(COD)(R,R-anthraphos)]BF₄, was prepared from
enantiopure anthraphos (II). The molecular and crystal structure of this catalyst was
analyzed by X-ray crystallography and compared with the known structures of chiraphos
and norphos. Use of [Rh(COD)(R,R-anthraphos)]BF₄ to hydrogenate (Z)-α-acetamidocinnamic
acid gave (S)-(+)-N-acetylphenylalanine in 90% e.e. Bisphosphine
VI was also used for the same purpose, but gave lower enantioselectivity. Different
ruthenium-anthraphos complexes were also synthesized by ligand exchange reactions in
an attempt to use them as asymmetric catalysts in the hydrogenation of C=C, C=O and
C=N bonds.
[chemical compound diagrams]
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Extent |
11199578 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-06-09
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0061500
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1995-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.