On the reactivity of tetrakis(trifluoromethyl)cyclopentadienone towards carbon-based Lewis bases.

The reactivitiy of tetrakis(trifluoromethyl)cyclopentadienone towards different C-based Lewis bases, such as N-heterocyclic carbenes (NHC), ylides and isonitriles, are reported. While sterically not hindered carbenes were found to yield kinetic adducts by regiospecific nucleophilic attack at the position adjacent to the carbonyl group of the ketone, bulkier nucleophiles afforded the thermodynamically more stable O-bridged zwitterions. Interestingly, isonitriles were found to dimerize and trimerize under the same reaction conditions, forming bicyclic products that evolve differently depending on the nature of the substituents.

Tuning the Lewis acidity of boranes in frustrated Lewis pair chemistry: implications for the hydrogenation of electron-poor alkenes.

An analysis of the metal-free reduction of electron deficient olefins by frustrated Lewis pairs indicates that the rate-determining step might be either the heterolytic cleavage of H2 to form an -onium borohydride salt, or the subsequent transfer of the hydride moiety to the substrate following a Michael-type addition reaction. While the use of strong Lewis acids such as B(C6F5)3 facilitates the first of these processes, hydride transfer to the olefin should be contrarily favoured by the use of weak Lewis acids which, for this very same reason, might be unable to promote the prior H2 split. After systematic testing of several boranes of different Lewis acidity (assessed by using the Childs' method) and steric demand, an optimal situation that employs tris(2,4,6-trifluorophenyl)borane was reached.

Synthesis and reactivity of electron poor allenes: formation of completely organic frustrated Lewis pairs.

The synthesis of several electron poor allenes bearing electron withdrawing substituents is described and their use as Lewis acids in the field of frustrated Lewis pair (FLP) chemistry reported. At room temperature the combination of N-heterocyclic carbenes (NHC) with the allenes under study invariably afforded the corresponding Lewis adducts; however, at -78 °C this reaction is in most of the cases inhibited and kinetically induced organic FLPs are formed. Under these conditions the activation of S-S bonds in disulfides has been achieved in excellent yields.

A nonsymmetric pincer-catalyzed Suzuki-Miyaura arylation of benzyl halides and other nonactivated unusual coupling partners.

The catalytic activity of a PCN-type palladium pincer complex is evaluated in the construction of C(sp(2))-C(sp(2)) and C(sp(2))-C(sp(3)) bonds by Suzuki-Miyaura cross-couplings employing nontypical substrates such as benzyl halides, alpha-haloenones, or alkylboronic acids as coupling partners. Most of the reported reactions are achieved in aqueous media, with all of the advantages implied.