MODEL REACTIONS FOR STERICALLY CONTROLLED SYNTHESES OF CYCLOHEX-2-ENONES WITH 4,4- OR 5,5-QUATERNARY CENTERS: A DIRECT CHIRAL SYNTHESIS OF 4-ALLYL-4-CYANOCYCLOHEX-2-ENONE FROM THE ANION OF (+)-TRICARBONYL(5-CYANO-2-METHOXYCYCLOHEXA-1,