Mechanistically Diverse Copper‐, Silver‐, and Gold‐Catalyzed Acyloxy and Phosphatyloxy Migrations: Efficient Synthesis of Heterocycles via Cascade Migration/Cycloisomerization Approach.

Abstract

Cycloisomerization Approach. -The cycloisomerization of alkynyl ketones and cyclic imines proceeds with concurrent migration of acyloxy and phosphatyloxy groups, respectively, to produce multisubstituted furans and fused pyrroles (to be continued). -(SCHWIER, T.; SROMEK, A. W.; YAP, D. M. L.; CHERNYAK, D.; GEVORGYAN*, V.; J. Am. Chem. Soc. 129 (2007) 32, 9868-9878; Dep. Chem., Univ. Ill., Chicago, IL 60607, USA; Eng.) -Bartels 50-120

Expanding the frontier of gold-catalyzed cyclizations and rational ligand design.

“…17,27,[75][76][77][78][79][80]142 However, the fact that the oxygen-transfer reaction of 2-alkynyl-1,5-diketones or 2-alkynyl-5-ketoesters could be completed in minutes at room temperature, and with higher yields than previously reported oxygen transfer prompted us to propose an alternative [4+2] mechanism (Scheme 20, bottom). We envisioned that a five-membered ring furanium C 8,20,[143][144][145][146][147][148][149][150][151][152] would be much easier to form than the seven-membered ring oxonium A, this action is followed by a [4+2] upfield chemical shift [153][154][155] was found on carbon 1 in the substrate, whereas no chemical shift change occurred on carbon 2. The 2-1b- 18 O substrate was subjected to the goldcatalyzed oxygen transfer reaction and the product 2-2b- Alongside our experimental studies, we turned to quantum chemical calculations to seek further verification that the proposed [4+2] mechanism was the preferred pathway and to understand the origins of this selectivity.…”