Gold(I)‐Catalyzed Addition of Diphenyl Phosphate to Alkynes: Isomerization of Kinetic Enol Phosphates to the Thermodynamically Favored Isomers

Abstract

Gold, gold, or …︁ gold? It depends on the (gold) catalyst whether the product of thermodynamic or kinetic control is formed in an unprecedented hydrophosphoryloxylation approach to enol phosphates (see scheme). A third catalyst, [(C6F5)3PAuOTf], was found to be exceedingly effective for the previously unknown isomerization of kinetic enol phosphates to the thermodynamically favored isomers. Tf=trifluoromethanesulfonyl; R=alkyl, cyclohexyl, Ph.

Gold(I)‐Catalyzed Stereoselective Synthesis of Alkenyl Phosphates by Hydrophosphoryloxylation

“…[12] Among a panoply of reagents, alkynes currently exist as the most prevalent substrates. [13] It is therefore not surprising that recently, Lee et al [14] reported the gold(I)-catalyzed addition of diphenyl phosphates to terminal alkynes for the selective preparation of alkenyl phosphates using various phosphanebearing gold centres in conjunction with silver salts as activators (Scheme 1). The choice of reaction conditions and catalytic system allow preparation of either the kinetic or thermodynamic product.…”

“…When 1 is activated by a Brønsted acid (HX) to generate [AuA C H T U N G T R E N N U N G (IPr)]X, relative conversion to either the kinetic or the thermodynamic alkenyl phosphate is dependent on the nature of X. With HNTf 2 no new product is observed ( [14] HOTf and HBF 4 all the starting material is converted ( 4 or AgOTf (5 mol %) as co-catalyst and the best result using this protocol provided an 80 % conversion of the thermodynamic phosphate product after overnight stirring at 50 8C with 5 mol % each of IPrAuCl and AgOTf. These results highlight the higher reactivity of IPrAuOH in combination with acids and the superior selectivity of the protocol, allowing the preparation of either kinetic or thermodynamic alkenyl phosphates as a function of the nature of the activating acid.…”

Gold-catalyzed oxycyclization of allenic carbamates: expeditious synthesis of 1,3-oxazin-2-ones

“…A general trend can be deduced on the basis of these results: heterocycle 4 is the thermodynamically controlled product while heterocycle 3 is the kinetically controlled product [71–73]. Probably, double-bond migration in compounds 3 results in the formation of the 1,3-oxazin-2-one 4 .…”

Ambient gold-catalyzed O-vinylation of cyclic 1,3-diketone: A vinyl ether synthesis

“…No general protocol for vinyl ether synthesis using gold has been reported to date [17]. Nevertheless, there have been examples regarding the intermolecular addition of carboxylic acids [19–20], phenols [21–22] as well as phosphoric acids [23–25] to alkynes. In this context, we report a gold(I)-catalyzed O-vinylation of 1,3-diketones with unactivated alkynes at ambient temperature.…”