Synthesis of SF₅CF₂-Containing Enones and Instability of This Group in Specific Chemical Environments and Reaction Conditions

Abstract

The chemistry of the SF5CF2 moiety has been scarcely investigated. In this report, we present synthetic pathways to a variety of SF5CF2-substituted compounds starting from vinyl ethers and SF5CF2C(O)Cl. In specific chemical environments and under particular reaction conditions, the SF5CF2 moiety is unstable in downstream products resulting in the elimination of the SF5(-) anion and its decomposition to SF4 and F(-). Surprisingly, the formed F(-) can attack the intermediate difluorovinyl moiety to form trifluoromethyl substituted products. This appears to happen when an intermediate neighboring group participation involving a double bond is possible. Under slightly different conditions, the reaction stops at the stage of a difluorovinyl compound.

Regioselective Gold-Catalyzed Hydration of CF3- and SF5-alkynes

“…Considered as a “super CF 3 ”, the pentafluorosulfanyl group (SF 5 ) has also recently attracted its share of attention for its unique and interesting properties including, among others, a large dipole moment, a high lipophilicity, and a strong electron-withdrawing capacity . Not surprisingly, this substituent has started to find use in various fields. , Contrary to the trifluoromethyl variant, access to α-SF 5 ketone compounds, despite their potential utility as SF 5 -containing building blocks, is far less developed, and only five single examples have been reported up to now (Scheme , eq 3) …”

Synthesis of α-(Pentafluorosulfanyl)- and α-(Trifluoromethyl)-Substituted Carboxylic Acid Derivatives by Ireland–Claisen Rearrangement

“…Subsequent conversion of the acids 8 into the methyl esters 15 allowed for a simpler isolation and purification of the γ,δ-unsaturated α-substituted carboxylic esters by column chromatography. Surprisingly, the initially used alkylation method (K 2 CO 3 , MeI, DMF, 0 °C, 3 h) did not exclusively give the target methyl esters 15 , since the SF 5 -group served as a leaving group and was partially substituted by a formate group, probably via an intermediate α-lactone (see SI). Therefore, the carboxylic acids 8 were treated with methanol in the presence of DCC and a catalytic amount of DMAP (Table ).…”

“…In the literature, several examples have been reported where the SF 5 group served as a leaving group, 38 and we found other examples more recently. 24 The decomposition of the SF 5 − anion to generate fluoride and SF 4 and subsequent decomposition of SF 4 might be a driving force for the reaction. 39 Procedure for Methylation of Carboxylic Acids 8f with MeI/K 2 CO 3 in DMF.…”

Silver-Promoted Synthesis of 5-[(Pentafluorosulfanyl)methyl]-2-oxazolines

“…For instance, palladium-catalyzed Suzuki–Miyaura cross-coupling of 3f with 4-methoxyphenylboronic acid under the standard conditions provided the desired product 5 in 84% yield. It is interesting to note that the pentafluorosulfanyl group is stable under the basic conditions used, even though elimination of a SF 5 group has been observed by others . Also, acid-promoted opening of oxazoline 3a with water followed by a treatment with acetyl chloride gave the fully protected SF 5 -containing amino alcohol 6 in 83% yield over two steps.…”