Fig. 4: Mechanistic studies.
From: Catalytic asymmetric synthesis of cannabinoids and menthol from neral
a, 1H NMR reaction monitoring to determine the reaction order in catalyst following Burés’ method29. b, Temporal 1H NMR concentration profiles31 of the reaction under different conditions. The rate differences show strong product inhibition in the cyclization reaction. c, Top, deuterium-labelled experiments with 85% C-8 labelled substrate 25. *The yield is determined by 1H NMR spectroscopy using mesitylene as an internal standard and is calculated on the basis of neral present in the sample (Z:E ratio = 70:30). Bottom, 2H NMR of the product mixture. d, Proposed catalytic cycle of the Brønsted acid-catalysed cyclization of neral. e, Free-energy profile for the cyclization reaction and the diastereo- and enantio-determining transition state TSAB. The strongest stereocontrolling interactions, C−H···F, are highlighted. f, Computed structure D, adduct of protonated product and catalyst 5.
