RESUMEN
Gold catalysis is a convenient tool to oxidatively functionalize alkyne into a range of valuable compounds. In this article, we report a new access to isochroman-4-one and 2H-pyran-3(6H)-one derivatives that involves a gold-catalyzed oxidative cycloalkoxylation of an alkyne in the presence of a pyridine N-oxide. The reaction proceeds under mild conditions, is relatively efficient and exhibits a high functional group compatibility.
Asunto(s)
Alquinos/química , Cromanos/química , Oro/química , Piranos/química , Catálisis , Cromanos/síntesis química , Ciclización , Oxidación-Reducción , Piranos/síntesis química , Piridinas/químicaRESUMEN
A study of the reaction of easily accessible 2-propynyloxy-6-fluoropyridines with arylamines under gold or silver catalysis is described. It has been shown that two types of isomeric oxazolopyridine imine derivatives, which represent unusual heterocyclic motifs, can be selectively obtained in moderate to excellent yields depending on the nature of the metal employed.
RESUMEN
2H-Azirines are easily synthesized from the corresponding ketones and, despite possessing a CN bond embedded in a strained three-membered cycle, they are sufficiently stable to be isolated, stored, and manipulated. 2H-Azirines can be regarded as valuable synthetic equivalents of alkenyl nitrenes, however, reactions capitalizing on the cyclic strain of the heterocyclic motif and involving the cleavage of the CN single bond remain surprisingly limited. A gold-catalyzed reaction that allows the formation of polysubstituted functionalized pyridines from easily accessible 2-propargyl 2H-azirine derivatives was developed. This transformation, which corresponds to an unprecedented intramolecular transfer of an alkenyl nitrene to an alkyne, proceeds with low catalyst loading, is efficient, and exhibits a high functional-group tolerance and a wide substrate scope.