Lewis Acid Catalyzed Synthesis of α-Trifluoromethyl Esters and Lactones by Electrophilic Trifluoromethylation
An electrophilic trifluoromethylation of ketene silyl acetals (KSAs) by hypervalent iodine reagents 1 and 2 has been developed. The reaction proceeds under very mild conditions in the presence of a catalytic amount of trimethylsilyl bis(trifluoromethanesulfonyl)imide (up to 2.5 mol %) as a Lewis acid providing a direct access to a variety of secondary, tertiary, and quaternary α-trifluoromethyl esters and lactones in high yield (up to 98%).
Katayev, Dmitry,Matou?ek, Václav,Koller, Raffael,Togni, Antonio
Activation of C-F bonds in preference to C-I bonds: Difluoromethylation of lithium enolates with trifluoromethyl iodide
(Figure Presented) The l's have it: A conceptually new C-F activation/C-C formation and its mechanism are described. Surprisingly, a reaction with Li-enolates and trifluoromethyl iodide gave (alpha)-difluoromethyl product via C-F bond cleavage in preference to the weaker C-I bond of trifluoromethyliodide. This reaction proceeds without the use of any late transitionmetal catalyst (see scheme; LHMDS = lithium hexamethyldlsilaxide).
Mikami, Koichi,Tomita, Yuichi,Itoh, Yoshimitsu
supporting information; experimental part
p. 3819 - 3822
(2010/09/04)
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