Fig. 4: Computed C–H activation pathways in the synthesis of carbohelicenes.
From: A C–H activation-based enantioselective synthesis of lower carbo[n]helicenes
C–H activation pathways calculated at the PCM(toluene)-B3LYP(D3)/SDD+def2-TZVP//B3LYP(D3)/SDD+def2-SVP level of theory (values in parentheses are ΔG (in kcal mol−1)). Two C–H activation pathways (red and blue arrows) starting from intermediates I-Ln and I*-Ln, that arise from oxidative addition and displacement of the bromide with the carboxylate group of the ligand, proceed with similar energy barriers and both contribute to the observed enantioselectivity. Subsequent deprotonation by caesium bicarbonate and coordination of Cs+ is exergonic and leads to intermediates III-Ln and III*-Ln, respectively. The Cartesian coordinates for the optimized structures are provided in the Supplementary Information.
