Gold(I)-Catalyzed Cycloisomerization of β-Alkynylpropiolactones to Substituted α-Pyrones

Abstract

Substituted α-pyrones were straightforwardly synthesized in good to excellent yields by a new gold(I)-catalyzed rearrangement of β-alkynylpropiolactones.

Ring Expansions of β-Lactams and β-(thio)lactones

“…β-Lactones with strong electron-withdrawing substituents are stable enough under the reaction conditions and are obtained in good yields. However, β-lactones without electron-withdrawing groups on the aromatic The synthesis of α-pyrones has been accomplished in good to excellent yields via rearrangement of β-alkynylpropiolactones catalyzed by gold complexes (Scheme 62) [65]. In order to find the optimal reaction conditions, various gold catalysts have been tested.…”

Gold‐Catalyzed Migrations and Ring Expansions

“…β-Alkynylpropiolactones can produce α-pyrones in high yields by a gold(I)-catalyzed cycloisomerization which involves the ring expansion of the four-membered ring lactone as shown in Scheme 96 164 .…”

Mechanistic insights and functionalization of alkynes in homogeneous gold catalysis.

“…[14][15][16][17][18][19] Unlike many transition metal catalyzed reactions, gold catalysis does not require anhydrous and air free conditions.…”

“…[68][69][70][71][72][73][74] In most gold catalyzed reactions, catalyst loadings in the 1-5% range are the norm. [14][15][16][17][18] One reason for the low turnover numbers (TON) is the relatively fast decay of cationic gold and its conversion into non-reactive species (e.g., Au [75][76][77][78][79] Despite this drawback, there has been no comprehensive systematic investigations on the decay of homogeneous gold catalysis, a stark contrast with the extensive work reported on catalyst deactivation in heterogeneous catalysis. 80 In this chapter, we answer some fundamental and intriguing questions on gold(I) decay, such as the effects of starting material, nucleophile, solvent, counterion and additives, and we offer a probable pathway for gold(I) decay.…”