Trialkylsily(trifluoromethyl)diazenes as Tailored Reagents for Nucleophilic Trifluoromethylation

Abstract

bond in 4 fulfills several useful functions by (i) providing a site for silver nitrate complexation, thus allowing easy separation, purification and storage of oily 4 ; (ii) introducing tricyclic strain, thus holding the labile rnethylene double bond in the exo-position, without danger of isomerization into the otherwise more stable endocyclic 5,6-p0sition~'~.~]; (iii) allowing access to new analogues of zizaene which have not yet been encountered in any natural products. Received: January 18, 1982 [Z 99 IE] German version: Angew. Chem. 94 (1982) 464 [ I ] Cf. P. Golitz, A. de Meijere, Angew. Chem. 89 (1977) 892; Angew. Chem. Int. Ed. Engl. 16 (1977) 854, and references cited therein. 121 According to a recent report, CF,I reacts with zinc metal in dimethylformamide when exposed to ultrasonic sound, forming a reagent which transfers CF? to carbonyl compounds. Cf. T. Kitazume, N. Ishikawa, Chem. Lett. 1981. 1679, and references cited therein.

Perfluoroalkylation with Organosilicon Reagents

“…Absence of the byproducts derived from singlet difluorocarbene supports such a masked nature of the “CF 3 - ” in this case. Relatively low efficiency of labile (trialkylsilyl)(trifluoromethyl)diazenes as trifluoromethylating agents reported by de Meijere et al can be explained in this context: CF 3 group in these species is further separated from the silicon center by two nitrogen atoms 46a…”

“…It is noteworthy that despite the fact that a plethora of hypercoordinate silicon species have been observed and fully characterized,46b all attempts to detect a putative pentavalent intermediate formed upon nucleophilic activation of 2 were unsuccessful. This is best explained by the kinetic instability of “CF 3 - ” anion and its preference for α-elimination and proton abstraction from the medium generating gaseous CF 3 H. Proton abstraction was observed even from acetonitrile or propionitrile when these solvents were employed in NMR experiments (eq 9).…”

Strategies for nucleophilic, electrophilic, and radical trifluoromethylations

“…For example, De Meijere and Hartkopf designed the trialkylsilyl(trifluoromethyl)diazenes 1 (Fig. 1) as tailored reagents for nucleophilic trifluoromethylation of carbonyl compounds to afford tertiary alcohols in moderate yields [10]. Following this pioneering work, trifluoromethylsilicon compounds 2-4 were prepared by Ruppert's group from the not yet banned trifluoromethyl bromide (Halon 1301) [11,12].…”

Research progress on trifluoromethyl-based radical reaction process

“…Thanks to the advent of Ruppert-Prakash reagent (Me 3 SiCF 3 ), now a tame nucleophilic trifluoromethylation is not a dream. (7)), and they introduced trialkylsilyl reagent in oranic field for the first time, and this reagent as was expected afforded tertiary alcohols in moderate yields [15]. Following this pioneering work, Ruppert and his coworkers prepared three trifluoromethylsilicon compounds ( Figure 2(8,9,10)) [16,17], but neither De Meijere nor Ruppert synthetically explored this new reagent until Prakash lucubrated what would later become extremely useful transformations and found it worked equally well with a wide array of aldehydes, ketones, enones, etc [18].…”