Alkynes as synthetic equivalents to stabilized Wittig reagents: intra- and intermolecular carbonyl olefinations catalyzed by Ag(I), BF3, and HBF4.
[reaction: see text] The first use of cationic silver (AgSbF4) as a catalyst for intra- and intermolecular alkyne-carbonyl coupling to form conjugated enones is described, and a comparison to corresponding Brønsted acid (HBF4) and Lewis acid (BF3) catalyst systems is made. Notably, intermolecular coupling proceeds stereoselectively to afford the corresponding trisubstituted enones as single geometrical isomers. This transformation represents a completely atom economical alternative to the use of stabilized Wittig reagents in carbonyl olefination and may be viewed as a formal alkyne-carbonyl metathesis.
Rhee
Jong Uk
JU
Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.
Krische
Michael J
MJ