The Lewis acid promoted reactions of 2‐substituted 2‐propenyl amides and the 2‐methylbuta‐2,3‐dienyl ester of ethenetricarboxylate have been examined. The reactions of 2‐substituted 2‐propenyl amides with AlCl3 gave 2‐oxo‐5,6‐dehydropiperidines as the major products. The reaction of 2‐methylbuta‐2,3‐dienyl ester with Lewis acids such as AlCl3 and SnCl4 gave 2‐oxo‐3,6‐dihydropyran as the major product. The preference for six‐ over five‐membered‐ring formation was observed.

Six-Membered Ring Formation from Lewis Acid Promoted Reactions of 2-Substituted 2-Alkenyl Amides and Esters of Ethenetricarboxylate. -Depending on the functionality of the substrates used, either saturated or unsaturated six-membered ring products are obtained selectively. The product formation is extensively investigated by DFT calculations. -(YAMAZAKI*, S.; UEDA, K.; FUKUSHIMA, Y.; OGAWA, A.; KAKIUCHI, K.; Eur. J. Org. Chem. 2014, 31, 7023-7033, http://dx.

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