Diverse continuous photooxygenation reactions of (+) and (−)-α-pinenes to the corresponding pinocarvones or trans-pinocarveols

Abstract

In this study, the continuous photooxygenation reactions of (+) and (−)-α-pinenes are described. The corresponding hydroperoxides were continuously processed under mild conditions using Ac₂O and a base to yield (−) or (+) pinocarvones in up to 79–83% yield and a 12–13 g-scale. Alternatively, the hydroperoxides were reduced with Ph₃P giving pinocarveols in up to 61% yield and a 10.8 g-scale. Our protocols proved to be efficient, easily scaled up and safe while processing unstable hydroperoxides in the g-scale (24 h experiments). Additionally, we describe a variable we named efficiency (E) which was useful to rationalize the best reaction conditions for the best yield, also including the productivity and non-processed starting materials.