Lewis acid promoted intramolecular hetero-[2 + 2] cycloadditions of ynamides: An equivalent of yn–carbonyl metathesis

ORGN 620

Kimberly C. M. Kurtz, kurtz@chem.umn.edu1, Richard P. Hsung, hsung@chem.umn.edu1, and Yanshi Zhang, yanshi@chem.umn.edu2. (1) Department of Chemistry, University of Minnesota, Smith Hall, 207 Pleasant St. SE, Minneapolis, MN 55455, (2) Department of Chemistry, University of Minnesota-Twin Cities, 207 Pleasant St. SE, Minneapolis, MN 55455
In recent years, ynamide chemistry has emerged as a field of interest for the development of new synthetic methodologies. Here, we report a new intramolecular reaction of ynamides that leads to the formation of unsaturated carbocyclic systems. Upon treatment with BF3-Et2O, an aldehyde or ketone that is tethered to an ynamide undergoes a formal oxa-[2 + 2] cycloaddition with the alkyne and subsequent ring opening to yield carbocycles of varying ring size. This transformation, which is an equivalent of yn - carbonyl metathesis, occurs rapidly even at low temperatures and gives the product in excellent yields.

 

New Reactions and Methodology
8:00 AM-12:00 PM, Wednesday, 16 March 2005 Convention Center -- Ballroom 20 C-D, Oral

Division of Organic Chemistry

The 229th ACS National Meeting, in San Diego, CA, March 13-17, 2005