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)-alpha,beta-unsaturated carboxylic acids. The reaction proceeds under mild conditions, tolerates a variety of functional groups and gives (E)-alpha,beta-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].