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Investigations relevant to semipinacol rearrangements for the formation of 1-azaspirocycles Easton, Leah Pearl
Abstract
Investigations related to semipinacol rearrangements for the formation of 1-azaspirocycles including substrate synthesis, reaction scope, and application to the Erythrina alkaloid skeleton are reported. Nickel(II) and chromium(II) salts are used to promote the addition of enol triflates derived from δ-valerolactam to aldehydes to produce substrates such as A. The use of N-Boc-protected triflate 1.21 results in higher yields than the corresponding N-Ts or N-Bz-protected analogues. Additions to aliphatic aldehydes are most efficient while electron-rich aldehydes prove less reactive. The optimized reaction conditions are also applicable to additions of 1.21 to cyclobutanone. The scope of the semipinacol rearrangement of siloxy-epoxides is extended to include substrates with larger rings. Using Lewis acid tin(IV) chloride the 6 to 7-membered and 7 to 8-membered ring expansions of the corresponding epoxides, 2.33 and 2.37, are possible. Two general strategies towards the Erythrina alkaloid skeleton which feature a sernipinacol rearrangement to form the spirocyclic ring junction are explored. However, both approaches are yet to provide a means to the total synthesis of the desired framework. During the course of investigations the semipinacol rearrangement of epoxide 3.59 involving a migration to a benzylic position is attained. [ Fomulas omitted ]
Item Metadata
Title |
Investigations relevant to semipinacol rearrangements for the formation of 1-azaspirocycles
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2007
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Description |
Investigations related to semipinacol rearrangements for the formation of
1-azaspirocycles including substrate synthesis, reaction scope, and application to the
Erythrina alkaloid skeleton are reported.
Nickel(II) and chromium(II) salts are used to promote the addition of enol
triflates derived from δ-valerolactam to aldehydes to produce substrates such as A.
The use of N-Boc-protected triflate 1.21 results in higher yields than the
corresponding N-Ts or N-Bz-protected analogues. Additions to aliphatic aldehydes
are most efficient while electron-rich aldehydes prove less reactive. The optimized
reaction conditions are also applicable to additions of 1.21 to cyclobutanone.
The scope of the semipinacol rearrangement of siloxy-epoxides is extended to
include substrates with larger rings. Using Lewis acid tin(IV) chloride the 6 to
7-membered and 7 to 8-membered ring expansions of the corresponding epoxides,
2.33 and 2.37, are possible.
Two general strategies towards the Erythrina alkaloid skeleton which feature
a sernipinacol rearrangement to form the spirocyclic ring junction are explored.
However, both approaches are yet to provide a means to the total synthesis of the
desired framework. During the course of investigations the semipinacol
rearrangement of epoxide 3.59 involving a migration to a benzylic position is
attained. [ Fomulas omitted ]
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Genre | |
Type | |
Language |
eng
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Date Available |
2011-02-22
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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 |
10.14288/1.0059832
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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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.