The diketoester 3 was synthesized from 2,4-pentanedione (1). After bis-allylation of 1 (NaH, s-BuLi, TMEDA, allylbromide, cyclohexane), [9] compound 2 was obtained in 34% yield (Scheme [2] ). Treatment of 2 with NaH, followed by addition of ethyl bromoacetate furnished an inseparable mixture of the desired monoalkylated compound 3 and the dialkylated product 3′. The mixture of 3/3′ was treated with Noyori's catalyst (R,R)-I, under hydrogen transfer conditions ...
