Deconstructing the Catalytic, Vicinal Difluorination of Alkenes: HF-Free Synthesis and Structural Study of p-TolIF2.

Recently, contemporaneous strategies to achieve the vicinal difluorination of alkenes via an I(I)/I(III) catalysis manifold were independently reported by this laboratory and by Jacobsen and co-workers. Both strategies proceed through a transient ArI(III)F2 species generated by oxidation of the ArI catalyst. Herein, an efficient synthesis of p-TolIF2 from p-TolI and Selectfluor is presented, together with a crystallographic and spectroscopic study. To mitigate safety concerns and simplify reaction execution, an HF-free protocol was devised employing CsF as a substitute fluoride source. The study provides insight into the initial I(I)→I(III) oxidation stage of the catalytic protocol using Selectfluor.

Iridium(I) N-Heterocyclic Carbene (NHC)/Phosphine Catalysts for Mild and Chemoselective Hydrogenation Processes.

The directed chemoselective hydrogenation of olefins has been established by using iridium(I) catalysts, which feature a tuned NHC/phosphine ligand combination. This selective reduction process has been demonstrated in a wide array of solvents, including more environmentally acceptable media, also allowing further refinement of hydrogenation selectivity.

Hydrogen isotope exchange with highly active iridium(I) NHC/phosphine complexes: a comparative counterion study.

Herein, we present a range of substrates that undergo hydrogen isotope exchange with an iridium(I) N-heterocyclic carbene/phosphine complex bearing the less coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]borate counterion and compare these with labelling using the equivalent, more established hexafluorophosphate complex. The changes in reactivity and selectivity of these complexes in a series of solvents are examined. Copyright © 2016 John Wiley & Sons, Ltd.

Iridium(I)-catalyzed regioselective C-H activation and hydrogen-isotope exchange of non-aromatic unsaturated functionality.

Isotopic labelling is a key technology of increasing importance for the investigation of new CH activation and functionalization techniques, as well as in the construction of labelled molecules for use within both organic synthesis and drug discovery. Herein, we report for the first time selective iridium-catalyzed CH activation and hydrogen-isotope exchange at the ß-position of unsaturated organic compounds. The use of our highly active [Ir(cod)(IMes)(PPh3 )][PF6 ] (cod=1,5-cyclooctadiene) catalyst, under mild reaction conditions, allows the regioselective ß-activation and labelling of a range of α,ß-unsaturated compounds with differing steric and electronic properties. This new process delivers high levels of isotope incorporation over short reaction times by using low levels of catalyst loading.

Gold(I)-catalyzed addition of thiols and thioacids to 3,3-disubstituted cyclopropenes.

Gold(I)-catalyzed reactions of thiols, thiophenols, and thioacids with 3,3-disubstituted cyclopropenes occur in a regioselective and chemoselective manner to produce either vinyl thioethers or primary allylic thioesters in good yields. A survey of commonly used gold(I) catalysts shows Echavarren's cationic gold(I) catalyst to be most tolerant of deactivation by sulfur. A novel digold with bridging thiolate complex is characterized by X-ray crystallography, shedding light on a possible deactivation pathway.

Divergent outcomes of gold(I)-catalyzed indole additions to 3,3-disubstituted cyclopropenes.

Depending on the conditions employed, gold(I)-catalyzed addition of indoles to 3,3-disubstituted cyclopropenes can be controlled to yield either 3-(E)-vinylindoles (3) or bis-indolylalkanes (4). If the cyclopropene substituents are sterically bulky, unprecedented gold-catalyzed oxidation under air occurs to yield bis-indolylalkene (5) and epoxide (6) at room temperature.