2002
DOI: 10.1246/cl.2002.282
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The 5-endo-trig Cyclization of gem-Difluoroolefins with sp3 Carbon Nucleophiles: Synthesis of 1-Fluorocyclopentenes

Abstract: A disfavored 5-endo-trig cyclization is accomplished in gem-difluoroolefins with sp3 carbon nucleophiles, generated via the lithium–iodine exchange reaction of 1,1-difluoro-5-iodo-1-pentenes with tert-butyllithium, to afford 1-fluorocyclopentenes.

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Cited by 21 publications
(8 citation statements)
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“…Difluoroalkenes have recently attracted considerable attention as synthetic building blocks . Among the various transformations, the intramolecular 5‐ endo ‐trig cyclization with nucleophiles developed by Ichikawa has given access to a wide range of fluorinated heterocycles . In the case of substrates 4 , this cyclization may lead to the unprecedented formation of fluorinated heterocyclic spiroindenes .…”
Section: Methodsmentioning
confidence: 99%
“…Difluoroalkenes have recently attracted considerable attention as synthetic building blocks . Among the various transformations, the intramolecular 5‐ endo ‐trig cyclization with nucleophiles developed by Ichikawa has given access to a wide range of fluorinated heterocycles . In the case of substrates 4 , this cyclization may lead to the unprecedented formation of fluorinated heterocyclic spiroindenes .…”
Section: Methodsmentioning
confidence: 99%
“…Nitrogennucleophile attacks preferentially CF 2 -carbon rather than the carbonyl carbon in difluorinated oc,P-unsaturated ester 32. 17 On the other hand, reaction can occur at the carbonyl carbon in nonfluorinated oc,P-unsaturated ester 34, 18 leading to lactam 35.…”
Section: Figure 10 Remarkable Reactivity Difference At ^-Carbon Betweenmentioning
confidence: 99%
“…Since we have already accomplished this type of 5-endo-trig cyclization by sp 3 carbanions [26] (see also [27] for 5-endo carbocyclization of gem-difluoroalkenes in the presence of SnCl 4 ), a phenyl anion of an sp 2 carbon nucleophile was adopted to broaden the scope of the nucleophilic 5-endo-trig ring closures (for the nucleophilic 5-endo-trig cyclization, see [9] and references therein). We expected the nucleophilic 5-endo-trig cyclization to proceed due to the unique properties of gem-difluoroalkenes: (i) the electrostatic attraction between the cationic CF 2 carbon and nucleophilic center (anion) would allow initial ring formation and (ii) the successive elimination of fluoride ion could suppress the reverse ring opening, thus functioning as a ''lock''.…”
Section: Synthesis Of 3-fluorinated Indenementioning
confidence: 99%
“…Thus, we have accomplished the 5-endo-trig cyclization with an sp 2 carbon nucleophile as well as sp 3 carbon nucleophiles [26], providing a regioselective entry to less accessible 3-fluoroindenes (for the synthesis of indenes bearing a fluorine on the five-membered ring, see: 3-fluoroindene: [31], 1-fluoroindene: [32]). …”
Section: Synthesis Of 3-fluorinated Indenementioning
confidence: 99%