Catalyst-controlled selectivity in the C–H borylation of methane and ethane

Abstract

The C-H bonds of methane are generally more kinetically inert than those of other hydrocarbons, reaction solvents, and methane functionalization products. Thus, developing strategies to achieve selective functionalization of CH4 remains a major challenge. Here, we report transition metal-catalyzed C-H borylation of methane with bis-pinacolborane (B2pin2) in cyclohexane solvent at 150°C under 2800 to 3500 kilopascals of methane pressure. Iridium, rhodium, and ruthenium complexes all catalyze the reaction. Formation of mono- versus diborylated methane is tunable as a function of catalyst, with the ruthenium complex providing the highest ratio of CH3Bpin to CH2(Bpin)2 Despite the high relative concentration of cyclohexane, minimal quantities of borylated cyclohexane products are observed. Furthermore, all three metal complexes catalyze borylation of methane with >3.5:1 selectivity over ethane.

Ruthenium(II)-catalysed remote C–H alkylations as a versatile platform to meta-decorated arenes

“…Since the substrates of interest display a variety of C–H bonds with close dissociation energies, achieving positional selectivity in intermolecular C–H transformations is paramount1112131415. Thus, chelation assistance has proven particularly instrumental for proximity-induced ortho -C–H functionalizations16171819.…”

Rare‐Earth Catalyzed C−H Bond Alumination of Terminal Alkynes

“…[1] Moreover,o rganoaluminumsc ombine nucleophilicitya nd Lewis acidity to offer reactivityp atterns, such as conjugate addition andf acile transmetalation, that are complementary to other useful reagents, including organomagnesium, -zinc, -copper and -lithium compounds.U nfortunately,s yntheses of complex organoaluminum compounds typicallyi nvolves alt-metathesis reactions that rely upon other alkylating agents and corrosive aluminumh alides. Ideally, direct metalationo fC ÀHb onds by inexpensive trialkylaluminums could greatly increase the availability of functionalgroup-containing organoaluminum compounds, but CÀH bond alumination is underdeveloped compared to otherc atalytic CÀHb ond functionalization methodss uch as borylation [2][3][4][5][6][7] or silylation. [8][9][10] Instead, mostC ÀHb ond alumination reactions rely on the inherentr eactivity of organoaluminum species.…”

Photocatalytic conversion of ethane: status and perspective

“…5 Most of ethane conversion processes are thermodynamically unfavorable at 298 K due to the positive ΔG 0 , except for ethane combustion with oxygen. 9 Given the harsh reaction condition and relatively high cost, a wide application of ethane functionalization in these homogeneous processes is rather difficult. Two pathways have been applied to catalytic ethane conversion to liquid fuels.…”