Table 1. Comparison of lignin^α–OX preparation protocols. Outcome of protocol assessed using 2D HSQC NMR and conversion assessed using semi-quantitative NMR analysis and reported as ratios with respect to the native β–O-4 unit A (oxidised state A′ and A′′) and the β–β unit C (for oxidised states C and D).38.

Method a	Temp. (time)	β–O-4 unit A : A′ : A′′	β–β unit C : D : E
DDQ stoich.	r.t (14 h)	1 : 1.4 : 2.2	1 : 0.6 : 0.4
	80 °C (2 h)	1 : 1.8 : 5.5	1 : 0.1 : 2.5
DDQ cat.8	80 °C (14 h)	1 : 0.6 : 1.2	1 : 0.1 : 0.2
TEMPO-MsOH stoich.30	65 °C (3 h)	1 : 1.3 : 1.6	1 : 0 : 0 b
Bobbitt's salt a stoich.9	r.t. (24 h)	1 : 1.4 : 2.4	1 : 0.2 : 0.1 b
	65 °C (3 h)	1 : 1.3 : 2.1	1 : 0.1 : 0.1 b

^aIt should be noted that although ref. 9 showed the oxidant Bobbitt's salt worked on model systems, this oxidant was not used on lignin in the original study. Unfortunately, several approaches could not be tested by us2,21,22 for reason that included challenges inherent in the use of high pressures of oxygen gas31 and the requirement for the use of electrochemistry equipment in a very recent report.32 See Fig. S18 and Table S6 for 2D HSQC NMR spectra. A and C integral values were normalised to a value of 1 for comparison. Values reported to one decimal place.

^bIn these reactions the starting β–β unit partially reacted but very little or no D or E was formed.