Nickel‐Catalyzed C_sp2−OMe Functionalization for Chemoselective Aromatic Homologation En Route to Nanographenes

Abstract

A Ni‐catalyzed Csp2−OMe ortho‐functionalization methodology to form chemoselectively alkyne monoannulation or aromatic homologation products is reported as a novel protocol towards the valorisation of substrates containing Csp2−OMe units. Double activation of Csp2−OMe and Csp2−F bonds is also demonstrated. Further use of aromatic homologation products towards the synthesis of nanographene‐like compounds is described.

Luminescent Chiral Furanol‐PAHs via Straightforward Ni‐Catalysed Csp2−F Functionalization: Mechanistic Insights into the Scholl Reaction

“…A more facile C sp2 À F over C sp2 À OMe functionalization was found in obtaining the aromatic homologation compounds 1 a and 1 b in good yields (63 % and 44 %, respectively). [16] Due to their facile synthesis, we took 1 a and 1 b as standard precursors for studying their ring-fusion in a variety of reported experimental conditions where we thoroughly analysed the nature of the oxidant and its concentration, the concentration of triflic acid and the reaction time. We previously reported that 1 a underwent double ring fusion along with hydrolysis and esterification of the AQ directing group.…”

“…We previously reported that 1 a underwent double ring fusion along with hydrolysis and esterification of the AQ directing group. [16] We have revisited the experimental conditions and found that under 5.0 equivalents of chloranil as oxidant and 429 equiv. of triflic acid the doubly fused compound 2 a was obtained in 32 % yield, where the AQ is left intact (Scheme 1).…”

“…We started our endeavour by taking advantage of the synthesis of aromatic homologation compounds via one‐step Ni‐catalysed C sp2 −F functionalization coupled with double insertion of diphenyl acetylenes. A more facile C sp2 −F over C sp2 −OMe functionalization was found in obtaining the aromatic homologation compounds 1 a and 1 b in good yields (63 % and 44 %, respectively) [16] . Due to their facile synthesis, we took 1 a and 1 b as standard precursors for studying their ring‐fusion in a variety of reported experimental conditions where we thoroughly analysed the nature of the oxidant and its concentration, the concentration of triflic acid and the reaction time.…”

“…[14] Here we take advantage of a straightforward chemoselective Ni-catalysed C sp2 À F activation of readily available substrates bearing the aminoquinoline (AQ) directing group (DG) for the synthesis of aromatic homologation compounds, [15] which are valid precursors for Scholl-like ring fusion (Figure 1). [16] Moreover, we took these aromatic homologation compounds as basic models and subjected them to a variety of Scholl-type experimental conditions (via oxidant and strong Lewis or Brønsted acid) to obtain a wide array of chiral PAHs as racemates, and we include their photophysical characterization as proof of the rich luminescent properties easily at hand. Remarkably, we report for the first time the synthesis of benzochryseno-furanol species, for which we provide full structural, as well as a mechanistic proposal for their formation, obtaining valuable insight into the highly unpredictable Scholl reaction.…”

“…Here we take advantage of a straightforward chemoselective Ni‐catalysed C sp2 −F activation of readily available substrates bearing the aminoquinoline (AQ) directing group (DG) for the synthesis of aromatic homologation compounds, [15] which are valid precursors for Scholl‐like ring fusion (Figure 1). [16] …”