Various 1,1-difluoro-1-alkenes such as monosubstituted 1,1-difluoro-1-alkenes, 2-bromo-1,1-difluoro-1-alkenes, and 3,3-difluoroallylic alcohols are synthesized in two simple steps from 1-trifluoromethylvinylsilane: (i) its SN2' reaction with nucleophiles to construct 2,2-difluorovinylsilanes and (ii) the subsequent substitution of electrophiles for the vinylic silyl group. The combination of these two processes allows a one-pot synthesis of the functionalized 1,1-difluoro-1-alkenes starting from 1-trifluoromethylvinylsilane, which functions as a CF2=C(-)-CH2+ synthon.
Catalytic
imidation using NFSI as the nitrogen source has become
an emerging tool for oxidative carbon–nitrogen bond formation.
However, the less than ideal benzenesulfonimide moiety is incorporated
into products, severely detracting its synthetic value. As a solution
to this challenge, we report herein the development of a novel N-fluorinated imide, N-fluoro-N-(fluorosulfonyl)carbamate (NFC), by which the attached imide
moiety acts as a modular synthetic handle for one-step derivatization
to amines, sulfonamides, and sulfamides. Furthermore, this study revealed
the superior reactivity of NFC as showcased in a copper-catalyzed
imidation of benzene derivatives and imidocyanation of aliphatic alkenes,
overcoming the limitation of NFSI-mediated reactions.
Efficient methods for the synthesis of fluorinated compounds have been intensively studied, recently. Development of practical fluorinating reagents is indispensable for this purpose. Herein, bench‐stable electrophilic fluorinating reagents were synthesized as N‐fluorobenzenesulfonimide (NFSI) substitutes. Reagents obtained by replacing one of the NFSI sulfonyl groups with an acyl group led to the highly selective monofluorination of silyl enol ethers with suppression of undesired overreaction, that is, difluorination. On the other hand, reagents bearing electron‐withdrawing substituents at NFSI benzenesulfonyl groups efficiently facilitated the difluorination of silyl enol ethers under base‐free conditions. Thus, both mono‐ and difluorinated target materials were prepared from the same substrate.
A drastic increase in catalyst turnover number (TON) was accomplished in the cross-metathesis of tetrafluoroethylene (TFE) and vinyl ethers. Under a continuous flow of TFE, catalyst Ru7, which contains a seven-membered N-heterocyclic carbene (NHC) ligand, reached a TON of 4100; this is 2 orders of magnitude higher than the highest hitherto reported value. Mechanistic studies revealed that the expanded NHC successfully destabilizes the stable intermediates with a difluorocarbene structure, which strongly promotes the reaction.
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