The gold(I)-catalyzed reaction of N-Boc-protected 6-alkynyl-3,4-dihydro-2H-pyridines, which affords synthetically useful vinylogous amides (beta-enaminones), has been studied in detail in order to optimize the reaction conditions, enlarge the scope and have insights into the mechanism and the structural features that selectively favor the 6-endo dig oxyauration of the triple bond. Experimental studies and DFT calculations demonstrate that the 6-endo dig approach is exclusive with substituted alkynes, whereas with terminal alkynes the 5-exo dig cyclization prevails despite the large angle (120°) at C6. The same selectivity is observed with N-Cbz-protected 2-alkynyl piperidines. With these, beta-amino ketones are obtained as a consequence of the 6-endo dig attack to a substituted triple bond. Sedamine alkaloids are easily obtained by this approach.

Gold-catalyzed Synthesis of Exocyclic Vinylogous Amides and beta-Amino Ketones. A Detailed Study on the 5-exo/6-endo dig Selectivity, Methodology and Scope / Dina Scarpi; Stefano Begliomini; Cristina Prandi; Alberto Oppedisano; Annamaria Deagostino; Enrique Gómez-Bengoa; Béla Fiser; Ernesto G. Occhiato. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1099-0690. - STAMPA. - 2015:(2015), pp. 3251-3265. [10.1002/ejoc.201500205]

Gold-catalyzed Synthesis of Exocyclic Vinylogous Amides and beta-Amino Ketones. A Detailed Study on the 5-exo/6-endo dig Selectivity, Methodology and Scope

SCARPI, DINA;OCCHIATO, ERNESTO GIOVANNI
2015

Abstract

The gold(I)-catalyzed reaction of N-Boc-protected 6-alkynyl-3,4-dihydro-2H-pyridines, which affords synthetically useful vinylogous amides (beta-enaminones), has been studied in detail in order to optimize the reaction conditions, enlarge the scope and have insights into the mechanism and the structural features that selectively favor the 6-endo dig oxyauration of the triple bond. Experimental studies and DFT calculations demonstrate that the 6-endo dig approach is exclusive with substituted alkynes, whereas with terminal alkynes the 5-exo dig cyclization prevails despite the large angle (120°) at C6. The same selectivity is observed with N-Cbz-protected 2-alkynyl piperidines. With these, beta-amino ketones are obtained as a consequence of the 6-endo dig attack to a substituted triple bond. Sedamine alkaloids are easily obtained by this approach.
2015
2015
3251
3265
Dina Scarpi; Stefano Begliomini; Cristina Prandi; Alberto Oppedisano; Annamaria Deagostino; Enrique Gómez-Bengoa; Béla Fiser; Ernesto G. Occhiato...espandi
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/983620
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