As global chemical manufacturing has historically relied on inexpensive feedstocks from the petrochemical industry, the identification of new naturally derived feedstocks represents an important and sustainable alternative. This review introduces Corymbia citriodora (Hook.) K.D.Hill & L.A.S.Johnson as an attractive renewable resource of natural compounds for organic chemical transformations. Although native to Australia, this plant species is now grown and harvested worldwide. The chemical composition of citriodora oils varies with location, harvesting season and age of leaves. Beyond their historic uses as fragrances or repellents, the more abundant terpenes found in citriodora oils such as citronellal, citronellol, and isopulegol have notable roles in the manufacture of fine chemicals. This review highlights several industrial processes intimately related to the citriodora terpenes, some advances in fragrances and repellents, as well as the use of these terpenes in the most recently reported synthesis of bioactive compounds. Where relevant, processes highlighting the adoption of green chemistry principles are presented and briefly discussed.

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Photooxygenations allow for the incorporation of molecular oxygen into substrates under mild and sustainable conditions. They only use light, oxygen and catalytic amounts of an organic dye to generate singlet oxygen (1O2), a short-lived reactive species, which can subsequently react with a multitude of functional groups within a substrate. Photooxygenations have found applications in fine chemical and pharmaceutical industries, for example in the manufacture of fragrances, building block chemicals and pharmaceuticals. Unlike batch processes, photooxygenations under flow conditions avoid accumulation of potentially explosive intermediates or products by continuously producing small amounts of materials, which can be subsequently quenched or converted safely. Continuous-flow reactors also allow for precise temperature control and the utilization of low-power light sources such as LEDs or OLEDs. The combination of flow operation, miniaturized dimensions and photooxygenations enables an environmentally friendly and safe adaptation to green organic synthesis. This chapter highlights various flow photoreactor technologies and successful examples of photooxygenations in flow.