Highly stereoselective ring expansion of enantiopure α-hydroxyalkyl azetidines

Couty, François; Durrat, François; Prim, Damien

doi:10.1016/s0040-4039(03)01227-9

Cited by 46 publications

(25 citation statements)

References 20 publications

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“…They can furthermore be expanded into other kinds of heterocycles including other heteroatoms. [25,30] We confirmed its stereospecificity and made some calculations [31] to examine the energetic profile of this rearrangement, and thus, it was confirmed that 58 is a viable (albeit never observed) intermediate. Ring expansion to pyrrolidines can be achieved by various strategies.…”

Section: Ring Expansion Of Azetidinesmentioning

confidence: 53%

2‐Cyanoazetidines and Azetidinium Ions: Scaffolds for Molecular Diversity

et al. 2013

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Ring strain in azetidines and azetidinium ions can be efficiently used to promote ring‐expansion and ring‐opening reactions, and this renders these four‐membered heterocycles ideal scaffolds for diversity oriented synthesis. This microreview focuses on 2‐cyanoazetidines, which are easily prepared from β‐amino alcohols through a ring‐closing reaction involving C–C bond formation. The azetidines can be readily expanded to five‐ to eight‐membered nitrogen heterocycles after suitable functionalization and/or activation. Alternatively, N‐alkylated derivatives, namely, azetidinium ions, are easily prepared and displayed rich reactivity as new electrophilic building blocks and as sources of nitrogen ylides.

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Section: Ring Expansion Of Azetidinesmentioning

confidence: 53%

2‐Cyanoazetidines and Azetidinium Ions: Scaffolds for Molecular Diversity

et al. 2013

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“…In our group, having devised a method for the stereocontrolled preparation of α-(hydroxymethyl)azetidines, we studied the behavior of a set of primary, secondary, and tertiary azetidinic alcohols involved in this ring expansion after transformation of the hydroxyl group into a leaving group (chloride or mesylate). This reaction [134,135] was found to occur in a stereospecific way and was general when primary and secondary alcohols were involved, as shown with several examples showing structures 292-299 in Scheme 74. However, it failed to produce any rearranged product in the case of tertiary alcohols.…”

Section: Expansions Into Pyrroles Pyrrolidin-2-ones and Pyrrolidinesmentioning

confidence: 82%

Ring Expansions of Nonactivated Aziridines and Azetidines

Couty

David

2015

Topics in Heterocyclic Chemistry

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Ring expansions promoted by ring strain in aziridines and azetidines are reviewed in this chapter, putting emphasis on recent applications from the last decade. This vast subject cannot be surveyed here exhaustively, and the reader will be guided to relevant precedent reviews or key reports. Rather, special attention will be put on selected examples and their mechanistic details, aiming to demonstrate that high selectivity can be reached in these reactions. In this issue, this fastgrowing topic has been divided into two distinct chapters, this one dealing with "nonactivated" aziridines and azetidines. Therefore, the reader will only find here examples involving NH-or N-alkylaziridines and N-azetidines as substrates for ring expansions, while N-acyl, N-carbamoyl, or N-tosyl compounds, defined as "activated" substrates, will be presented in the next chapter. This distinction can appear quite arbitrary at first sight but is amply justified by the great difference in reactivity of these distinct substrates. The first part focuses on the ring expansions of nonactivated aziridines into up to seven-membered rings and is further divided into expansions involving the incorporation of one (or more) heteroatoms, followed by ring expansions involving only incorporation of carbon atoms. The same model is then followed for azetidines.

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“…Compounds 3 and 4 were treated with tetrabutylammonium fluoride in dry THF. Whereas amino ethers 4 were desilylated to afford a complex mixture of products,16,17 azetidines 3 , under the same conditions gave bicyclic compounds 5 . The product 5a (R = Ph) was recrystallized and an X‐ray analysis18 of this compound (Figure 3) showed a cis relative configuration for each heterocycle, thus establishing an ( S ) absolute configuration at the ring junction (Scheme ).…”

Section: Resultsmentioning

confidence: 99%