Aluminum Chloride Catalyzed Reaction of Acetanilide with Pivalyl Chloride

Product development was studied in the aluminum chloride catalyzed reaction of acetanilide with pivalyl chloride. 3-tert-Butylacetanilide is the major product because of its relative resistance to dealkylation by reaction-produced HCl. At long reaction times all alkylation products are converted back to acetanilide with the only survivor being 2,2-dimethyl-5-tert-butyl-7-acetamidoindanone. The crystal structure of this compound was determined. It crystallized in the space group P_nmawith cell constants a = 12.571 (3) Á, b = 7.302 (1) Å, c = 16.910 (3) Å, V = 1552.24 ų, z = 4. Refinement of the 1224 data with F²⩾ 3σF²) resulted in discrepancy indices R₁= 0.056 and R₂= 0.074. A novel mechanism for formation of this indanone is proposed, involving nucleophilic attack by alkene on a protonated arene ring.