Reactivity of Biomass‐Derived Olefins with Elemental Sulfur: Mechanistic Insight

The reactivity of biomass-derived aryl olefins with elemental sulfur was studied at 180 and 230 °C and at three different sulfur/organic substrate ratios. Products resulting from a range of mechanisms were unveiled, including inverse vulcanization, S−C_{allylic/benzylic} bond formation, S−C_aryl bond formation, intramolecular cyclization, C−C σ-bond scission, and C−O σ-bond scission.

Abstract

Lignocellulosic biomass remains underutilized despite its annual production in gigaton quantities. Sulfur is another vastly underutilized waste product of fossil fuel refining. New mechanistic insight into the reactions of sulfur unveiled since 2020 suggest a rich and hitherto unexplored chemistry between biomass-derived olefins and elemental sulfur. In this study, four biomass-derived olefins (eugenol (1), 4-allyl-2,6-dimethoxyphenol (2), o-eugenol (3), and 2-allyl-6-methylphenol (4)) were reacted with elemental sulfur to elucidate the S−C bond-forming and other reactivity of these compounds. Each of the compounds was reacted with elemental sulfur in three sulfur : organic reactant ratios (2 : 1, 4 : 1 and 9 : 1) and at two temperatures (180 °C or 230 °C). Product mixtures were characterized using ¹H NMR spectrometry and GC-MS analysis. Products resulting from a range of mechanisms were unveiled, including inverse vulcanization, S−C_{allylic/benzylic} bond formation, S−C_aryl bond formation, intramolecular cyclization, C−C σ-bond scission, and C−O σ-bond scission. It is anticipated that the insights from this study will support further synergy between the critical sustainability goals of biomass and sulfur utilization.

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