Gold(I)‐Catalyzed Cyclizations of 1,6‐Enynes: Alkoxycyclizations and exo/endo Skeletal Rearrangements

Abstract

Gold(I) complexes are the most active catalysts for alkoxy- or hydroxycyclization and for skeletal rearrangement reactions of 1,6-enynes. Intramolecular alkoxycyclizations also proceed efficiently in the presence of gold(I) catalysts. The first examples of the skeletal rearrangement of enynes by the endocyclic cyclization pathway are also documented. Iron(III) is also able to catalyze exo and endo skeletal rearrangements of 1,6-enynes, although the scope of this transformation is more limited. The gold(I)-catalyzed endocyclic cyclization proceeds by a mechanism different from those followed in the presence of PdII, HgII, or RhI catalysts.

Gold and Platinum Catalysis of Enyne Cycloisomerization

“…[11,28] The minor product 162 corresponded to the expected cycloisomerization process, which was discussed above. The major product, however, was determined to be methylenecyclohexene 161, corresponding to a new reaction manifold.…”

“…In 2004, as a part of their comprehensive study of gold-based catalysis of enyne cycloisomerizations, Echavarren and co-workers reported that cationic gold complexes were exceedingly effective in promoting alkoxycarbocyclizations of a wide range of 1,6-enynes. [11,28] A representative scope of this process, as well as the typical reaction conditions, is shown in Scheme 27.…”

Cycloisomerisierungen von 1,n‐Eninen: faszinierende metallkatalysierte Umlagerungen und mechanistische Einblicke

“…[168] Malacria et al [132] hatten schon früher die Reaktivität von Eninamiden in Gegenwart von Platin untersucht und eine ähnliche Reaktivität festgestellt, wenn auch bei höherer Temperatur [siehe Gl. [149,150,173] oder auf Gold(III)-Vorstufen [115,174] [Gl. (152) + zu erzeugen.…”

Gold(I) Complexes of KITPHOS Monophosphines: Efficient Cycloisomerisation Catalysts

“…[8] The similarity be- tween KITPHOS and Buchwalds biaryl monophosphines, combined with the fact that the latter have proven to be very successful ligands for a vast array of gold-catalysed transformations [9] prompted us to synthesise gold complexes of these KITPHOS monophosphines and investigate their applications in a selection of gold-catalysed cycloisomerisations.…”