Sonnenenergie in der Organischen Chemie: Photokatalytische Elektrosynthese eines Pheromons

Abstract

A completely sun-powered photocatalytic electrosynthesis of the pheromone (±)-4-methyl-3-heptanone (1) from ethyl bromide (2) and 2-methyl-1-penten-3-one (3) is described. Solar energy is used simultaneously 1. for homogeneous photochemistry using vitamin B₁₂ as photo- and electrocatalyst, 2. for biasing the cell voltage with Si solar cells, and 3. for solvent convection. The sun-reactor produced 1 at an average rate of ca. 170 mmol per m² of total sun-exposed surface area and per day (24 h, August in Bern). This corresponds to an efficiency of ca. 1∙10^-8 mol/J at an average solar radiation input of ca. 200 W/m². Selective C–C-bond formation in the sun-reactor is supposed to be of general applicability.