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This review article comprehensively profiles all literature reports (2015-2018) related to the detrifluoroacetylative in situ generation of fluorine-containing enolates and their reactions with electrophilic reagents. The innovative facets of this unconventional methodology and its synthetic generality for the preparation of fluorine-containing compounds of high medicinal value are highlighted.

Mannich-type addition of 1,3-dicarbonyl compounds to (SS)-N-tert-butanesulfinyltrifluoroacetaldimine has been carried out under dramatically different conditions. The stereochemical outcome was quite different when the reaction was carried out under solvent-free conditions, at high temperature and without any catalyst or additive, compared with the DBU catalyzed reaction in dichloromethane solution at low temperature. Mechanistic aspects of the reaction under both the conditions are discussed. In this respect, vibrational (VCD) and electronic circular dichroism (ECD) and optical rotatory dispersion (ORD) experiments proved to be valuable tools for determining the absolute configurations of the reaction products.

Elimination from 3α-chloro-3β-methyl-(1) and 3β-chloro-3α-methyl-5α-cholestane (2) to give 3-methylene-5α-cholestane (exo-olefin) and 3-methyl-5α-cholest-2-ene (endo-olefin) has been investigated in ButOK–ButOH solution. The exo:endo olefin ratio is affected by the ButOK concentration but does not depend significantly upon the conformation of the chlorine substituent. This also holds for the reaction rates since the endo-olefin is formed at 100° only 1.7 fold faster from (1)(axial chlorine) than from (2)(equatorial chlorine). In contrast, elimination from 3α-chloro-5α-cholestane (3) is ca. 500 fold faster than from the equatorial isomer (4). The small difference between (1) and (2) in the rate of formation of the endo-olefin is due to compensation between enthalpy and entropy factors. A similar situation is also observed when the exo-olefin forming reactions from (1) and (2) are considered. The kinetic data and the activation parameters support the hypothesis that both olefins are formed from (2) in an anticoplanar process involving a skew-boat conformation.

The lack of a significant leaving group effect and the preferential departure of the ‘poorer’ leaving group suggest an irreversible E1cb mechanism for the title reactions.

The oxidation of 1,2- diphenylethane and 2,3-dimethyl-2,3-diphenylbutane by cerium(IV) ammonium nitrate and Co(OAc)3 in acetic acid show that a radical cation mechanism is plausible only in the reaction of the former oxidant.