10.1021/jo202183u.s001 Heather K. Lenker Heather K. Lenker Marcia E. Richard Marcia E. Richard Kyle P. Reese Kyle P. Reese Anthony F. Carter Anthony F. Carter Jason D. Zawisky Jason D. Zawisky Eric F. Winter Eric F. Winter Timothy W. Bergeron Timothy W. Bergeron Krysta S. Guydon Krysta S. Guydon Robert A. Stockland Robert A. Stockland Phospha-Michael Additions to Activated Internal Alkenes: Steric and Electronic Effects American Chemical Society 2012 latter alkenes ditolylphosphinic acid Electronic EffectsThe addition ethyl cinnamate microwave reactor addition reaction ditolylphosphine oxide substrate phosphine oxide Activated Internal Alkenes methyl crotonate room temperature 2012-02-03 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Phospha_Michael_Additions_to_Activated_Internal_Alkenes_Steric_and_Electronic_Effects/2553469 The addition of P­(O)–H bonds to internal alkenes has been accomplished under solvent-free conditions without the addition of a catalyst or radical initiator. Using a prototypical secondary phosphine oxide, a range of substrates including cinnamates, crotonates, coumarins, sulfones, and chalcones were successfully functionalized. Highly activated acceptors such as isopropylidenemalononitrile and ethyl 2-cyano-3-methyl-2-butenoate underwent the phospha-Michael reaction upon simple trituration of the reagents at room temperature, whereas less activated substrates such as ethyl cinnamate and methyl crotonate required heating (>150 °C) in a microwave reactor to achieve significant consumption of the starting alkenes. For the latter alkenes, a competing reaction involving disproportionation of the ditolylphosphine oxide into ditolylphosphinic acid and ditolylphosphine was observed at the high temperatures needed to promote the addition reaction.