ChemInform Abstract: Gold‐Catalyzed Synthesis of Exocyclic Vinylogous Amides and β‐Amino Ketones: A Detailed Study on the 5‐exo/6‐endo‐dig Selectivity, Methodology and Scope.

Abstract

Gold-Catalyzed Synthesis of Exocyclic Vinylogous Amides and -Amino Ketones:A Detailed Study on the 5-exo/6-endo-dig Selectivity, Methodology and Scope. -The Au(I)-catalyzed reaction of N-Boc-protected 6-alkynyl-3,4-dihydro-2H-pyridines, giving vinylogous amides (-enaminones), is studied in detail. Experimental studies and DFT calculations demonstrate that the 6-endo-dig approach is exclusive with substituted alkynes, whereas with terminal alkynes 5-exo-dig cyclization prevails. The same selectivity was observed with N-Cbz-protected 2-alkynylpiperidines to afford -amino ketones due to a 6-endo-dig attack onto a substituted triple bond. Sedamine alkaloids become easily accessible based on this method. -(SCARPI*, D.; BEGLIOMINI, S.; PRANDI, C.; OPPEDISANO, A.; DEAGOSTINO, A.; GOMEZ-BENGOA, E.; FISER, B.; OCCHIATO, E. G.; Eur. J. Org. Chem. 2015, 15, 3251-3265, http://dx.doi.org/10.1002/ejoc.201500205 ; Dip. Chim., Univ. Stud. Firenze, I-50019 Sesto Fiorentino, Italy; Eng.) -T. Stabingis 37-172Cl -