Base-induced rearrangements of bicyclo[2.2.1] and bicyclo[2.2.2]alkene-derived epoxides to ketones and alcohols

Hodgson, David M.; Marriott, Robert E.

doi:10.1016/s0040-4039(96)02432-x

Cited by 9 publications

(7 citation statements)

References 7 publications

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“…Lithium amide-induced rearrangement of exo-norbornene oxide 43 gave nortricyclanol 44 in up to 90 % yield, depending on the base employed (Scheme 5.11) [15,21,22]. Lithium amide-induced rearrangement of exo-norbornene oxide 43 gave nortricyclanol 44 in up to 90 % yield, depending on the base employed (Scheme 5.11) [15,21,22].…”

Section: Transannular C-h Insertions In Epoxides Of Polycyclic Alkenesmentioning

confidence: 99%

“…Similarly, epoxides 45 and 47 gave alcohols 46 and 48, respectively [21,23]. An intriguing reaction was found to occur with exo,exo-norbornadiene dioxide 51; presumably epoxide 52, the direct result of transannular insertion, was highly strained and so was reduced by the excess of LDA present to give meso-diol 53 [15,22]. An intriguing reaction was found to occur with exo,exo-norbornadiene dioxide 51; presumably epoxide 52, the direct result of transannular insertion, was highly strained and so was reduced by the excess of LDA present to give meso-diol 53 [15,22].…”

Section: Transannular C-h Insertions In Epoxides Of Polycyclic Alkenesmentioning

confidence: 99%

“…Whereas exo-norbornene oxide rearranges to nortricyclanol on treatment with strong base through transannular C-H insertion (Scheme 5.11), endo-norbornene oxide 64 gives norcamphor 65 as the major product (Scheme 5.14) [15,22]. This product arises from 1,2-hydrogen migration; very little transannular rearrangement is observed.…”

Section: Isomerization Of Epoxides To Ketonesmentioning

confidence: 99%

“…This product arises from 1,2-hydrogen migration; very little transannular rearrangement is observed. In comparison, the sense of product distribution is reversed for the related substrate bicyclo[2.2.2]octadiene oxide 70 on treatment with LDA [15,22], alcohol 72 being the favored product. 15), which once again indicates that close proximity between the carbenoid center and the C-H bond into which it may insert is important if such an insertion is to occur [30].…”

Section: Isomerization Of Epoxides To Ketonesmentioning

confidence: 99%

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Metalated Epoxides and Aziridines in Synthesis

Hodgson

Bray

2006

Aziridines and Epoxides in Organic Synthesis

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The chemistry of epoxides and aziridines is dominated by reactions that involve cleavage of the strained heterocyclic ring by nucleophiles (see Chapters 7 and 12). However, a less well known aspect of the chemistry of epoxides and aziridines is that which occurs upon reaction with a strong base. Abstraction of a b-proton may occur, resulting in the formation of allylic alcohols or amines, a process termed belimination [1a]. However, the b-hydrogens are not usually the most acidic; due to the electron-withdrawing effect of the oxygen/nitrogen and the acidifying nature of the three-membered ring, removal of an a-proton can occur to give an a-metalated epoxide (oxiranyl anion) or aziridine (aziridinyl anion) 1 (Scheme 5.1).The chemistry of a-metalated epoxides and aziridines (the a prefix will from now on not be included but should be assumed) has been reviewed previously [1], but in this chapter it is our intention to focus on those reactions involving them that are useful in synthesis, rather than just of pedagogical interest. Beginning with metalated epoxides, since the greater amount of work has involved them, we intend to present carefully chosen examples of their behavior that delineate the diverse nature of their chemistry. We will then move on to metalated aziridines, the chemistry of which, it will become apparent, closely mirrors that of their epoxide cousins.

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Section: Transannular C-h Insertions In Epoxides Of Polycyclic Alkenesmentioning

confidence: 99%

Section: Transannular C-h Insertions In Epoxides Of Polycyclic Alkenesmentioning

confidence: 99%

Section: Isomerization Of Epoxides To Ketonesmentioning

confidence: 99%

Section: Isomerization Of Epoxides To Ketonesmentioning

confidence: 99%

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Metalated Epoxides and Aziridines in Synthesis

Hodgson

Bray

2006

Aziridines and Epoxides in Organic Synthesis

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“…For the related bicyclo[2.2.2]octadiene oxide (58), under similar reaction conditions to above, the main product was tricyclic alcohol (59, Scheme 20). 22,41 Preferential generation of 59 might be explained by a p-s* C-H orbital overlap that promotes the C-H insertion both at the lithiated epoxide and/or carbene stage.…”

Section: Scheme 19mentioning

confidence: 99%

Recent Developments in the Chemistry of Lithiated Epoxides

Hodgson¹,

Gras²

2002

Synthesis

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106

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Although the lithium base-induced b-elimination of epoxides to allylic alcohols is a well-known reaction, a-lithiation has also been described many times. The resulting lithiated epoxides, first postulated as intermediates by Cope in 1951, have been invoked in a wide range of reactions, with their carbenoid properties allowing for very different reactivities. This review covers the recent advances (~1996-mid 2002) in the rich chemistry of these main-group metal carbenoids, especially their generation by enantioselective a-deprotonation.

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