Ringing the Changes: A Remarkable Carbene‐Free Synthesis of Difluorocyclopropenes

Fluoroalkenyl, fluoroalkynyl and fluoroalkyl phosphines

“…The identity of this second product was initially inferred from multinuclear NMR data; the fluorine NMR spectrum displayed a doublet (J(PF) = 4 Hz) at À103.3 ppm whilst the 13 C{ 1 H} data showed triplets due to coupling with two fluorine nuclei at 106.2 (J(CF) = 273 Hz), 122.7 (J(CF) = 14 Hz) and 149.2 ppm (J(CF) = 10 Hz). These data are consistent with those previously observed for the gem-difluorocyclopropene unit obtained in a similar reaction on silicon based systems [60]. Because this cyclisation reaction is not observed for less sterically demanding RLi reagents we have suggested that steric congestion which resulted following the addition of t-BuLi across the triple bond resulted in elimination of LiF and concomitant cyclisation.…”

“…One other area where the greater reactivity of these compounds becomes obvious is on reaction with alkyl lithium reagents. Previously we have shown that reaction of a main-group trifluoropropynyl compound with t-BuLi results in two possible products after work-up, one of which corresponds to an unusual cyclisation process [60]. The reaction of t-BuLi with i-Pr 2 PCBBCCF 3 dissolved in ether was studied at a series of different temperatures.…”

M-CPOnes: Transition Metal Complexes with Cyclopropenone-Based Ligands for Light-Triggered Carbon Monoxide Release

“…Furthermore, the difluorocyclopropene derivatives were stable during purification by column chromatography on silica gel. This was surprising since other difluorocyclopropenes and related difluorocyclopropanes are susceptible to hydrolysis under relatively mild conditions, 38,56,74 including on silica gel, 56,81,86,88 giving the corresponding cyclopropenones and cyclopropanones, respectively. Indeed, attempted hydrolysis of 3a-c to cyclopropenones 1a-c on a small scale under a variety of mild conditions (wet CDCl3, Amberlyst ® 15 or silica gel at room temperature for 24 h) 38,56,74,80 revealed the stability of the difluorocyclopropenes (SI, Section 4); while there was no hydrolysis of 3c under these conditions (Figure S58, A-C), derivatives 3a-b showed partial hydrolysis using Amberlyst ® 15 and silica gel (Figures S56-S57, B-C) and no hydrolysis in CDCl3 (Figures S56-S57, A).…”

“…‡ The C=C bond length (1.33 Å) and C-F bond lengths (1.38 Å) in the cyclopropene ring are similar to those in related difluorocyclopropenes. 86,87 Although synthetic access to the desired difluorocyclopropenes was initially envisaged to be challenging, the cycloaddition strategy was tolerant of both the 2,2'-bipyridine coordination motif and a second heterocyclic 6-quinoline substituent. Furthermore, the difluorocyclopropene derivatives were stable during purification by column chromatography on silica gel.…”

Perfluoroalkylation

“…A mechanistically completely different method for obtaining difluorocyclopropenes (Scheme 3.80) does not depend on addition of difluoromethylene [153]. [153]. The resulting vinyllithium species has very close contact between lithium and one fluorine atom of the trifluoromethyl group, facilitating extrusion of lithium fluoride.…”