Configuration of stilbene derivatives by 1H NMR and theoretical calculation of chemical shifts

Mechanistic analysis by NMR spectroscopy: A users guide

A 'principles and practice' tutorial-style review of the application of solution-phase NMR in the analysis of the mechanisms of homogeneous organic and organometallic reactions and processes. This review of 345 references summarises why solution-phase NMR spectroscopy is uniquely effective in such studies, allowing non-destructive, quantitative analysis of a wide range of nuclei common to organic and organometallic reactions, providing exquisite structural detail, and using instrumentation that is routinely available in most chemistry research facilities. The review is in two parts. The first comprises an introduction to general techniques and equipment, and guidelines for their selection and application. Topics include practical aspects of the reaction itself, reaction monitoring techniques, NMR data acquisition and processing, analysis of temporal concentration data, NMR titrations, DOSY, and the use of isotopes. The second part comprises a series of 15 Case Studies, each selected to illustrate specific techniques and approaches discussed in the first part, including in situ NMR (^1/2H, ^10/11B, ¹³C, ¹⁵N, ¹⁹F, ²⁹Si, ³¹P), kinetic and equilibrium isotope effects, isotope entrainment, isotope shifts, isotopes at natural abundance, scalar coupling, kinetic analysis (VTNA, RPKA, simulation, steady-state), stopped-flow NMR, flow NMR, rapid injection NMR, pure shift NMR, dynamic nuclear polarisation, ¹H/¹⁹F DOSY NMR, and in situ illumination NMR.

Synthesis of a Benvitimod Impurity: (Z)-3,5-Dihydroxy-4-Isopropylstilbene

(E)-3,5-dihydroxy-4-isopropylstilbene (Benvitimod), a new medicine for the treatment of psoriasis and eczema, belongs to the hydroxystilbene family. The synthesis leads to the E-isomer, (Z)-3,5-dihydroxy-4-isopropylstilbene being present as a major impurity in the preparation of Benvitimod. We describe a synthesis of the Benvitimod impurity: (Z)-3,5-dihydroxy-4-isopropylstilbene starting from 3,5-dihydroxybenzoic acid, through an isopropyl reaction, esterification and etherification, reduction, oxidation, Perkin condensation, decarboxylation and demethylation. The optimal reaction conditions were also determined.