On the Superior Activity of In(I) versus In(III) Cations Toward ortho-C-Alkylation of Anilines and Intramolecular Hydroamination of Alkenes

Abstract

An efficient ortho-C-alkylation of unprotected anilines with a variety of styrenes and alkenes using a univalent cationic indium(I) catalyst is reported. Mechanistic studies revealed that the reaction likely proceeds via a tandem hydroamination/ Hofmann−Martius rearrangement. The high compatibility between the cationic indium(I) complex and primary anilines led us to develop an In(I) + -catalyzed hydroamination of alkenes using unprotected primary and secondary alkenylamines. Computations support the catalytic activity of naked In(I) + ions, with an outer sphere mechanism for the C−N bond formation and a potentially inner sphere protodemetallation.

Hydroboration and Deoxygenation of CO2 Mediated by a Gallium(I) Cation

“…Spectroscopic data suggest that under hydroboration conditions, gallium remains in the +3 oxidation state after initial oxidation, although the mechanism, speciation, and true role of gallium and organoborane species in reduction of CO 2 to formate remain to be clarified. These results hint at the potential for further development of reactive gallium cations in catalysis. ,, The lack of reactivity of the hydridogallium dication [(Me 4 TACD)­GaH] 2+ toward CO 2 contradicts established reactivity patterns of electropositive metal hydrides and additionally prompts further studies of this unusual system.…”

“…These results hint at the potential for further development of reactive gallium cations in catalysis. 28,63,64 The lack of reactivity of the hydridogallium dication [(Me 4 TACD)GaH] 2+ toward CO 2 contradicts established reactivity patterns of electropositive metal hydrides and additionally prompts further studies of this unusual system.…”

Nickel(ii)/Lewis acid catalysed olefin hydroamination and hydroarylation under mild conditions

“…8,9 To date, catalytic addition of versatile olefins to anilines to construct the C-N bond for aniline derivative synthesis has been well documented, and a wide variety of noble metalbased catalysts, Lewis acid (LA) and Brønsted acid based catalysts have been explored. [10][11][12][13][14][15][16][17][18][19][20][21][22] For example, in 2000, Kawatsura and Hartwig reported a Pd(TFA) 2 catalysed hydroamination of styrene under acidic conditions (Scheme 1a). 23 In 2005, Bergman and co-workers developed a Brønsted acid catalysed synthesis with a PhNH 3 B(C 6 F 5 ) 4 •Et 2 O catalyst at an elevated temperature (135 °C) (Scheme 1b), 24 and in 2011 Li reported a Lewis acid, that is, Zn(OTf ) 2 , catalysed synthesis also at an elevated temperature (130 °C) (Scheme 1c).…”

Selective Acid-Catalyzed Hydroarylation of Nonactivated Alkenes with Aniline Assisted by Hexafluoroisopropanol

“…On a large scale, the C-functionalization of aniline is thus restricted to the methyl group (Scheme ), which limits the possibility of tuning the physicochemical properties of polyurethanes, the biggest market share of aniline . Driven by increasing environmental concerns and associated stringent legislation, the chemical industry is seeking clean technologies to C-functionalize aniline. − In this context, the hydroarylation of alkenes with aniline has become a reaction of interest, as it provides an access to C-functionalized aniline derivatives in a 100% atom-economical fashion (Scheme ).…”