SNi′ displacements with main group organometallics

Devambatla, Ravi Kumar Vyas; Velagaleti, Ranganadh; Yarravarapu, Nageswari; Fleming, Fraser F.

doi:10.1016/j.tet.2012.02.001

Cited by 19 publications

(22 citation statements)

References 110 publications

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“…S N i′ displacements with propargyllic electrophiles are rare, 10 in large part because of the difficulty in generating anionic nucleophiles in the presence of reactive propargylic electrophiles. Metalated nitriles, although not used previously for S N i′ displacements, are ideal because of their facile formation through deprotonation, 11 halogen-metal, 12 sulfoxide-metal, 13 and sulfide-metal 14 exchange and because their formation is highly tolerant of delicate functionality.…”

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confidence: 99%

Metalated nitriles: SNi′ cyclizations with a propargylic electrophile

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Pakkala

Evanseck

et al. 2015

Tetrahedron Letters

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A rare 5-exo-dig SNi′ cyclization with magnesiated and lithiated nitriles affords a cis-fused hydrindane bearing an exocyclic allene. The cyclization of the dilithiated nitrile pits a stereoelectronic preference for a trans-hydrindane against a cyclization through a less strained transition structure to the corresponding cis-hydrindane. Computational modeling suggests that the dilithiated nitrile cyclizes to a cis-hydrindane because the preferred transition structure positions the lithium cation in a cone of electron density that bridges the nitrile-bearing carbon, an alkoxide, and an electron-rich alkyne functionality.

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confidence: 99%

Metalated nitriles: SNi′ cyclizations with a propargylic electrophile

Lü

Pakkala

Evanseck

et al. 2015

Tetrahedron Letters

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“…[10] The S N i displacements via 5a and 7a and the S N i' displacements via 5b and 7b , correspond to favorable 6-exo-tet and 6-endo-trig processes, respectively. [11] Conceptually, the greater flexibility imparted from the single, rotatable bonds in the forming cyclohexane rings of 5a and 7a , allows an optimal orbital alignment for the S N i displacement.…”

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confidence: 99%

“…No prior mechanistic analysis has probed the relative preference for S N i versus S N i' displacements of metalated nitriles, despite the potential use of the strategy for installing hindered quaternary centers. [10] …”

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confidence: 99%

“…[17] Potentially, the small size and high nucleophilicity of metalated nitriles might overcome the propensity for a competitive S N i' resulting from the increased steric demand, [10] and instead favor S N i displacement. The strategy is attractive because numerous terpenoids contain decalins having contiguous quaternary-tertiary centers.…”

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confidence: 99%

“…[10] Deprotonation of the E/Z -mixture of 34 at −78 °C afforded the dilithiated nitrile 35 which, upon warming to rt for 15 min, afforded the trans -decalin-nitrile 36 bearing contiguous quaternary centers (Scheme 10). Although the reaction was not as clean as prior S N i displacements, there was no evidence for cis -diastereomers or diastereomers arising from competitive S N i displacement.…”

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confidence: 99%

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