(2) with ethyl crotonate under a variety of conditions failed to afford 1. The reaction of the dianion of 2 (2.1 equiv of i-Pr2NLi, 0 OC or-78" C) with crotonoyl chloride furnished variable yields of 1. However, generation of keto ester 3 followed by reaction with the potassium tert- butoxidetert-butyl alcohol complex13 provided a 45% yield of 1. A distinctive feature of the proton NMR spectrum of 1 is a sharp singlet around 6 6.1 for the vinylic hydrogen at C-2. ...
