In a different approach (Scheme 2) for the synthesis of lb, we explored the direct introduction of diethylcarbamoyl group on compound 5.16 Thus, 3-isopropyl-lmethoxybenzene was acylated with diethylcarbamoyl chloride in the presence of aluminum chloride to furnish a mixture of 3b and 3c in a 70: 30 ratio. Our efforts to improve this ratio under a variety of reaction conditions were unsuccessful. Since the separation of the two isomers 3b and 3c ...
