STEREOSELECTIVE SYNTHESIS OF 7-MEMBERED CARBOCYCLES FROM 2-AMINO-1,3-BUTADIENES AND VINYL CHROMIUM FISCHER-TYPE CARBENES

Seven-membered ring carbocycles are prepared by reaction of easily avaliable 2-amino-1,3-butadienes with vinyl Fischer carbenes. Hydrolysis of the cycloadduct initially formed gives rise to cyclohepta-1,3-diones with total regio- and stereoselectivity in a one-pot process. When 2-aminobutadienes bearing a prolinol derivative as a chiral auxiliary are used, the corresponding cyclic diketones are obtained with very high enantiomeric excesses. The absolute configuration of the stereogenic centers generated was determined with the aid of ROESY and CD measurements.