A Persistent α‐Fluorocarbanion and Its Analogues: Preparation, Characterization, and Computational Study

Abstract

Starkes Fluor: In Einklang mit theoretischen Studien zu α‐Fluorcarbanionen ergab eine Röntgenstrukturanalyse für das α‐Fluorbis(phenylsulfonyl)methid‐Anion eine pyramidale Konfiguration (siehe Bild). Anspruchsvolle Rechnungen und NMR‐spektroskopische Studien zeigten, dass elektronenziehende Substituenten die Eigenschaften von Bis(phenylsulfonyl)methid‐Anionen entscheidend beeinflussen.

Nucleophilic Fluoromethylation of Aldehydes with Fluorobis(phenylsulfonyl)methane: The Importance of Strong Li–O Coordination and Fluorine Substitution for CC Bond Formation

“…Secondly [6] These proton affinity data indicate that among these three anions, (PhSO 2 ) 2 CF À possesses the highest basicity and the lowest leaving-group ability, which is in good agreement with our experimental result that 3 is the most stable lithium carbinolate species among 3-5. [14] Thirdly, we investigated the gas-phase Gibbs free energies of three addition reactions between carbanions 8-10 (9 = (PhSO 2 ) 2 CH À Li + ; 10 = (PhSO 2 ) 2 CCl…”

From Difluoromethyl 2‐Pyridyl Sulfone to Difluorinated Sulfonates: A Protocol for Nucleophilic Difluoro(sulfonato)methylation

“…As depicted in Table 6, all the nucleophilic substitution reactions are shown to be thermodynamically favorable at the B3LYP/6-311 + G level. [14] Moreover, the reactions of CH 3 Br with 12 b and 12 c are of substantial energetic preference over those involving 12 d-12 f, and is in good agreement with the experimental outcomes. The cleavage of the SÀCX 2 bond was also found to be thermodynamically allowed in light of the dimerization of the carbenes; however, in comparison with 12 d-12 f, the decomposition of 12 b,c is less likely to occur due to the formation of thermodynamically less stable sulfinates.…”

“…Finally, to manifest the structure-reactivity relationship observed for various aryl sulfones, computational studies based on the density functional theory (DFT) were performed at the B3LYP/6-311 + G(2d,p) level. [14] As shown in Table 6, significantly lower bond orders were found to be associated with difluoromethides (12 b-12 f), thus indicating weaker SÀCX 2 bonds compared with the non-fluorinated analogue (12 a). In contrast with the S À CH 2 bond in 12 a that possesses partial double bond character, the S À CF 2 bond lengths are calculated to be much longer than that of the typical C sp 3 ÀSO 2 bonds (1.764-1.790 ), [15] thus suggesting the absence of resonance.…”

“…The addition of hexamethylphosphoramide (HMPA) was found to be necessary, which improved the yield to 45 % when lithium hexamethyldisilazide (LiHMDS) was used as the base (Table 1, entries 5 and 6). Further lowering the temperature to À98 8C gave a considerably higher yield ( [13][14][15]. With exhaustive optimization of the proportion of the substrates, the best reaction conditions were established as 1.0 equivalent of iodide reacting with 1.3 equivalents of sulfone 1 b and 1.5 equivalents of LiHMDS in THF/ HMPA (10:1, v/v) 11 and 12) revealed that LiHMDS was the most suitable base.…”

Development of Shelf-Stable Reagents for Fluoro-Functionalization Reactions

“…We estimated that the fluorination reaction with Me-NFSI under Lewis acid catalysis should occur more smoothly due to the higher basicity of sulfonyl oxygens of Me-NFSI than those of NFSI. In addition, methanesulfonimide (41) Figure 3. Shelf-stable reagents for fluorination and fluorofunctionalization designed by our group.…”