Combined Transition-Metal- and Organocatalysis: An Atom Economic C3 Homologation of Alkenes to Carbonyl and Carboxylic Compounds

A combination of regioselective room-temperature/ambient-pressure hydroformylation (transition-metal catalysis) and decarboxylative Knoevenagel reactions (organocatalysis) allowed for the development of an efficient, one-pot C3 homologation of terminal alkenes to (E)-alpha,beta-unsaturated acids and esters, (E)-beta,gamma-unsaturated acids, (E)-alpha-cyano acrylic acids, and alpha,beta-unsaturated nitriles. All reactions proceed under mild conditions, tolerate a variety of functional groups, and furnish unsaturated carbonyl compounds in good yields and with excellent regio- and stereocontrol. Further, an iterative C2 homologation of (E)-alpha,beta-unsaturated carboxylic acids is possible through a combination of decarboxylative hydroformylation employing a supramolecular catalyst followed by decarboxylative Knoevenagel condensation with an organocatalyst.