Nicolas Roques

BiCl3-catalyzed Friedel–Crafts acylation reactions: bismuth(III) oxychloride as a water insensitive and recyclable procatalyst

Abstract The Friedel–Crafts acylation of activated and polycyclic aromatics is efficiently catalyzed by bismuth(III) chloride which is generated in situ from bismuth(III) oxychloride, a water insensitive and eco-friendly material. Bismuth(III) oxychloride is easily recovered in near quantitative yields after an aqueous work-up.

Nucleophilic perfluoroalkylation of diaryldisulfides with perfluorocarboxylate salts

Abstract A new industrial and economical route to trifluoromethyl aryl sufides by thermal decarboxylation of trifluoroacetate salts has been recently developed. The possibility of generalising this reaction of “trifluorodecarboxylation” to R f CO 2 K (R f : CCl 3 , CF 2 Cl, CF 3 CF 2 , CF 3 CF 2 CF 2 ) in order to synthesise R f SAr has been studied. Thus, the reaction was effective with R f CO 2 K (R f =CCl 3 , CF 3 CF 2 ) and a new route to aryl pentafluoroethyl sufides CF 3 CF 2 SAr has been briefly exemplified.

N-Fluorocinchonidinium tetrafluoroborate F-CD-BF4: purification and structure elucidation of this novel enantioselective electrophilic fluorinating agent

Abstract The first ever enantiopure N -fluoro quaternary ammonium salt of cinchonidine (F-CD-BF 4 ) was prepared as an enantioselective fluorinating agent. A one-step transfer-fluorination of the quinuclidine moiety with Selectfluor® gave the [NF] + reagent. The X-ray structure of F-CD-BF 4 was determined, which shows the NF distance (1.409(7) A) close to that found in other NF compounds.

Metal triflates–methanesulfonic acid as new catalytic systems: application to the Fries rearrangement

A surprising synergistic effect has been discovered between metal triflates (Mg, Ca, Sc, Cu, Zn, Y, Ln, Bi) and methanesulfonic acid, leading to active catalytic systems for the Fries rearrangement. In particular, the systems based on yttrium and copper(II) triflate proved to be very active and much cheaper than scandium triflate. The efficiency of these systems might result from the catalytic Lewis acid activation of Bronsted acids.

Hemiaminals of trifluoroacetaldehyde, as trifluoromethylating agents

Abstract Hemiaminals of trifluoroacetaldehyde are new trifluoromethylating agents. These reagents are synthesised from amines and gaseous trifluoroacetaldehyde. tBuONa is able to deprotonate the hemiaminals to form trifluoromethyl anion equivalents CF 3 CH(O − )NMe 2 . The trifluoromethyl anion has been transferred from such intermediates to benzaldehyde yielding phenyl (trifluoromethyl) methanol.

Molar scale electrosynthesis of ethyl-2,2-difluoro-2-trimethylsilylacetate, a difluoromethylene building block precursor

Abstract Ethyl-2,2-difluoro-2-trimethylsilylacetate has been prepared by electrolysis of ethyl-2-chloro-2,2-difluoroacetate in one step, at a molar scale, in the presence of a large excess of chlorotrimethylsilane. The transfer of the ethyl-2,2-difluoroacetate moiety to various electrophiles has been achieved.

Selective electrochemical synthesis and reactivity of functional benzylic fluorosilylsynthons

Abstract Electrochemical reductive silylation of meta -(trifluoromethyl)arenes by the sacrificial anode technique selectively led to meta -trimethylsilyldifluoromethylarenes (ArCF 2 TMS), in the presence of an excess of TMSCl and in a THF/cosolvent mixture (cosolvent=DMPU or HMPA). In the case of meta -(trimethylsilyldifluoromethyl)trifluoromethylbenzene, the influence of the cosolvent on the silylation selectivity was studied. A cyclic voltammetry study allowed an explanation of the difference in the results obtained between the trifluoromethylbenzene and meta -bistrifluoromethylbenzene series. ArCF 2 TMS (Ar=Ph, m -CF 3 C 6 H 4 ) species were found efficient for ArCF 2 -group transfer to diverse electrophiles under Fuchigami’s conditions (KF catalysis in DMF).

Bismuth(III) bis(trifluoromethanesulfonyl)amide

Abstract Bismuth(III) bis(trifluoromethanesulfonyl)amide (Bi(NTf 2 ) 3 , 3 ) has been prepared from the reaction of protiodemetallation of tri- p -tolylbismuth by a stoichiometric amount of bis(trifluoromethanesulfonyl)amine ( 1 ). The intermediates BiPh 3− n (NTf 2 ) n ( n =2 ( 4 ), 1 ( 5 )) resulting from the reaction of 1 with triphenylbismuth have also been isolated. The amide 3 was able to catalyze the benzoylation and the benzenesulfonylation of toluene.

Non-defluorinative electrochemical silylation of ethyl trifluoroacetate: a practical synthesis of trifluoroacetyltrimethylsilane via its ethyltrimethylsilyl ketal

Abstract An efficient method for the preparation of original trifluoroacetyltrimethylsilane, CF 3 COSiMe 3 ( 3 ), in two steps from readily available ethyl trifluoroacetate is described. Electrochemical reduction of this ester using a sacrificial anode and performed on a semimolar scale afforded the unprecedented corresponding ketal, CF 3 C(SiMe 3 )(OSiMe 3 )OEt ( 2 ) in 30–56% isolated yield. Treated with concentrated sulphuric acid at room temperature, the latter directly led to pure acylsilane 3 in 86% yield.