Carbocyclization reactions of terminally difluorinated alkenyl active methine compounds mediated by SnCl4 and amine

Phosphate esters as “tunable” reagents in organic synthesis

“…39 2,3-Allenyl phosphates were likewise suitable substrates for the palladium-catalyzed asymmetric amination or imidation reactions. 40 Benzyl phosphates, contrary to benzyl sulfonates, [41][42][43] were not reported to react either with cyanide ions or intermolecularly with other carbon nucleophiles such as malonate anion. An intramolecular nucleophilic substitution by the anion from a nitrile or by a tert-butyl ester enolate onto a benzyl phosphate, however, offered an interesting way for the formation of five-membered rings, as in the asymmetric synthesis of N-tert-butyl disubstituted pyrrolidines 44 and in building cyclopentane rings bearing three consecutive chiral centers.…”

Ring-fluorinated naphthalene and indene synthesis via 6- and 5-endo-trig cyclizations of gem-difluoroalkenes by carbon nucleophiles

“…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''.…”

Ring-size-selective construction of fluorine-containing carbocycles via intramolecular iodoarylation of 1,1-difluoro-1-alkenes

“…In the course of our studies on the cationic cyclization of 1,1-difluoro-1-alkenes, we undertook an investigation of their iodine-mediated cyclization. Three-membered iodonium intermediates generated in the reaction course were expected to exhibit switchable regioselectivities [ 22 ]. This is because their cationic charge might be less localized on the carbon atoms α to the fluorine substituents, as compared to the aforementioned cationic intermediates [ 23 – 27 ].…”