Evidence for regioselective Pt(II)-mediated hydroxylation of long linear alkanes in acetic acid

© 2018 Selective functionalization of hydrocarbons remains one of the most challenging reactions in organic chemistry. With respect to terminal C–H hydroxylation, electrophilic activation by late transition metals has been considered a promising route. We report the use of Shilov-chemistry inspired Pt catalysis in acetic acid as suitable solvent for the formation of primary alcohols from long linear alkanes. By reacting n-heptane with K2PtCl4 under an oxygen atmosphere, a positional selectivity of 18% was reached for 1-heptanol among the C7 alcohols at significantly high conversion (37%). Moreover, we provide evidence for the intrinsic activity of Pt(II), along with elucidation of the role of specific additives as coordinating ligands. Both acetic anhydride (AA), initially added as protecting agent, and sulfuric acid proved to be essential to obtain an active alkane hydroxylation system; via ESI-MS [Pt(AA)(OSO3H)3(H2O)]+ and [Pt(CH3COOH)(OSO3H)3(H2O)]+ were identified in the active catalytic system. Furthermore, nonselective overoxidation originates from various side reactions, for which a reaction network is proposed. Finally, the stability of the in situ formed esters was studied in detail by recording time-dependent profiles for the decomposition of different positional isomers of n-octyl acetate, as well as of its fluorinated analogues. Altogether, these results illustrate the clear potential of the proposed concept in forming primary alcohols directly from cheap and abundant alkanes.

Publication year:2018

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BOF-publication weight:10

CSS-citation score:1

Authors from:Higher Education

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