Practical Synthesis of ( E )‐α,β‐Unsaturated Carboxylic Acids Using a One‐Pot Hydroformylation/Decarboxylative Knoevenagel Reaction Sequence

Combining the regioselective room temperature/ambient pressure hydroformylation and a modification of the Doebner–Knoevenagel reaction allowed for the development of an efficient, one‐pot procedure for the synthesis of ( E )‐α,β‐unsaturated carboxylic acids. The reaction proceeds under mild conditions, tolerates a variety of functional groups and gives ( E )‐α,β‐unsaturated carboxylic acids in good yields and with excellent regio‐ and stereocontrol. The practicability of this process has been demonstrated by a short protecting group‐free synthesis of the queen honeybee pheromones 9‐ODA [( E )‐9‐oxodec‐2‐enoic acid] and 9‐HDA [( E )‐9‐hydroxydec‐2‐enoic acid].