*3.6. NMR Spectroscopy*

NMR analyses were conducted to validate the presence and amount of the main reaction products and to obtain insight into the nature of major byproducts. For NMR analyses, samples were condensed on a rotary evaporator at 40 ◦C and re-dissolved in deuterated acetonitrile (>99.8 atom% deuterium). NMR spectra were recorded on an 800 MHz Bruker Avance II spectrometer equipped with a 18.7 T magne<sup>t</sup> (Oxford, United Kingdom) and a TCI z-gradient cryoprobe (Bruker, Karlsruhe, Germany) at 25 ◦C. The 2D NMR spectra included TOCSY with a 10 kHz spin lock field that was applied for 60 ms (2048 × 256 complex data points with 640 ms and 80 ms acquisition times), a sensitivity enhanced 1H-13C HSQC (1024 × 1024 complex points, sampling 128 ms and 73 ms acquisition times), 1H-13C HMBC (2048 × 256 complex data points, sampling 213 and 11 ms acquisition times) and a 1H-13C HSQC TOCSY (1024 × 512 complex points with 107 ms and 42 ms acquisition times). Identification of byproducts in reaction mixtures were done by comparison to pure reference standards (e.g., acetic and benzoic acid) or by de novo structure determination (e.g., 2-methoxy-1,4-benzoquinone). All spectra were acquired in Bruker Topspin and processed in the same software with extensive zero filling in all dimensions.
