Hydrovinylation Reactions in Organic Synthesis

Codimerization of ethylene and various functionalized vinylarenes, 1,3-dienes, or strained alkenes can be carried out in the presence of nickel, ruthenium, or cobalt complexes in very high yields and exceptional regio- and stereoselectivities. Nickel appears to provide the most active catalyst, even though more recent work indicates that the other metals may have unique advantages of their own. Many of these reactions proceed under exceedingly mild conditions (-50. °C to 25. °C, 1. atm of ethylene) to produce valuable intermediates including 3-arylbutenes and skipped 1,4-dienes with a chiral carbon at the benzylic or bis-allylic center. The 3-arylbutenes can be transformed into nonsteroidal antiinflammatory drugs such as ibuprofen, naproxen, and fenoprofen in two steps. Cyclic and acyclic 1,3-dienes also undergo efficient addition of ethylene and terminal alkenes catalyzed by either Ni(II), Ru(II), or Co(II) complexes. The regio- and stereoselectivities of many of these reactions can be controlled by judicious choice of metals and ligands. In addition, the hydrovinylation reaction can be used to generate molecules with an all-carbon quaternary center. These discoveries open expeditious routes to several biologically relevant classes of compounds including bisabolanes, herbindoles, trikentrins, steroid-. D-ring 20(. S) or 20(. R)-derivatives, pyrrolidinoindolines, pseudopterosins, and various members of the serrulatane and amphilectane classes of compounds. © 2014 Elsevier Ltd. All rights reserved.