Stereoselectivity of cyclization of substituted 5-hexen-1-yllithiums: regiospecific and highly stereoselective insertion of an unactivated alkene into a carbon-lithium bond

doi:10.1021/JA00015A028

Paper

Stereoselectivity of cyclization of substituted 5-hexen-1-yllithiums: regiospecific and highly stereoselective insertion of an unactivated alkene into a carbon-lithium bond

Published Jul 1, 1991 · W. Bailey, A. Khanolkar, K. Gavaskar

Journal of the American Chemical Society

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88

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Abstract

Substituted 5-hexen-1-yllithiums, which were prepared in solutions of n-C 5 H 12 -Et 2 O (3:2 by vol) by low-temperature lithium-iodine exchange between t-BuLi and the appropriate iodide, undergo clean, 5-exo-trig cyclization upon warming to give substituted (cyclopentyl)methyllithiums, in good yield and with a high degree of stereocontrol. In each case, the major product is the same isomer as that observed in studies of the isomerization of analogously substituted 5-hexen-1-yl radicals, but the organolithium cyclizations are invariably much more stereoselective than radical-mediated processes. Lewis base additives such as THF, TMEDA, and PMDTA serve to increase the rate of cyclization of the substituted 5-hexen-1-yllithiums, but such additives do not reduce the high stereoselectivity of the process. The observed regioselectivities and stereoselectivities of the intramolecular addition of a C-Li bond to an unactivated alkene suggest that the closure of the anion proceeds via a transition state that resembles a chair cyclohexane in which substituents preferentially occupy pseudoequatorial positions

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Study Snapshot

Substituted 5-hexen-1-yllithiums undergo clean, 5-exo-trig cyclization to give substituted (cyclopentyl)methyllithiums with high stereoselectivity, suggesting a transition state resembling a chair cyclohexan

PopulationOlder adults (50-71 years)

Sample size24

MethodsObservational

OutcomesBody Mass Index projections

ResultsSocial networks mitigate obesity in older groups.

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Paper

Stereoselectivity of cyclization of substituted 5-hexen-1-yllithiums: regiospecific and highly stereoselective insertion of an unactivated alkene into a carbon-lithium bond

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References

Citations

Computational insight into 1,2-diamine, -diether, and -amino ether chiral ligands-mediated carbolithiation: a case of enantioinduction reversal.

Diether and amino ether ligands show high enantioselectivities in asymmetric intramolecular carbolithiation of olefinic aryllithiums, with the most efficient ones resulting from favorable weak interactions between the ligand and substrate.

Lithium–Olefin π-Complexes and the Mechanism of Carbolithiation: Synthesis, Solution Behavior, and Crystal Structure of (2,2-Dimethylpent-4-en-1-yl)lithium

Lithium-olefin -complexes show potential for accelerating olefin carbolithiation reactions, with THF displacent olefin interactions and accelerating the rate of carbolithiation.

Organolithium-mediated cyclization reactions: a practical way to access hetero- and carbocycles

Organolithium-mediated cyclization reactions offer a practical method for designing and synthesizing new hetero- and carbocyclic compounds using simple and commercially available organolithium reagents.

Sulfone-Metal Exchange and Alkylation of Sulfonylnitriles.

Sulfone-metal exchange and alkylation of sulfonylnitriles can rapidly produce quaternary nitriles with minimal organometallic reagents.

Synthesis of (R)‐(−)‐Muscone from (R)‐5‐Bromo‐4‐methylpentanoate: A Chiron Approach

This study presents a chiral approach for the synthesis of (R)-muscone, a valuable musk odorant, using methyl (R)-5-bromo-4-methylpentanoate and ring-closing metathesis.

Intramolecular carbolithiation cascades as a route to a highly strained carbocyclic framework: competition between 5-exo-trig ring closure and proton transfer

Intramolecular carbolithiation cascades can produce highly strained carbocyclic frameworks, but they are limited by proton transfer, preventing the formation of the stellane framework.