The First Gold‐Catalyzed CS Bond Formation: Cycloisomerization of α‐Thioallenes to 2,5‐Dihydrothiophenes

Abstract

One good ring deserves another: A highly efficient and stereoselective cycloisomerization of α‐thioallenes to 2,5‐dihydrothiophenes is the first example of a gold‐catalyzed carbon–sulfur bond formation (see scheme, X=Cl, I). Both gold(I) and gold(III) salts can be used as the precatalyst, with AuCl and AuI giving the best yields. The method is of interest for the stereoselective synthesis of biologically active 2,5‐disubstituted dihydro‐ or tetrahydrothiophenes.

Organometallic Approaches to Carbon–Sulfur Bond Formation

“…Pd(PPh 3 ) 4 allene hydrothiolation carbonylation sequence [183] In 2006, Krause and Nakamura independently reported the first examples of Aucatalyzed transformations of sulfur-containing reagents [11,247]. These reports are particularly notable, as they dispel the myth of sulfur-gold incompatibility.…”

“…Indeed, the use of metal catalysts, including copper, palladium, rhodium and gold, now represents a widely employed synthetic strategy for installation of C-S bonds. The functional group compatibility of these processes continues to increase [11][12][13][14][15], which has led to applications of metal-mediated C-S bond formation in complex molecule synthesis [16][17][18]. Despite these advances, there is continued pressure to develop more efficient and versatile methods.…”

Reactions of Cycloaliphatic Thioketones and Their Oxo Analogues with Lithiated Methoxyallene: A New Approach to Vinylthiiranes

“…As key conclusion can be stated that the allenyl thiols derived from alkoxyallenes and thioketones do not require an external Brønsted or Lewis acidic catalyst for the cyclizations. [20] By contrast, the allenyl alcohols obtained from the corresponding ketones can be isolated and they lead either to vinyloxiranes or to 2,5-dihydrofurans depending on the substrate and on the type of the catalyst applied. Whereas in certain cases traces of acid lead to slow 1,3-cyclization, addition of catalytic amounts of Au I /pyridine-complex or of base leads preferentially to the five-membered product.…”

Transition-Metal-Catalyzed S–H and Se–H Bonds Addition to Unsaturated Molecules

“…AuBr 3 -catalyzed regioselective hydrothiolation of aromatic allenes with arenethiols affords the corresponding dithioketals in good yields under mild conditions [79]. Intramolecular hydrothiolation of a-thioallenes to 2,5-dihydrothiophenes is successfully catalyzed by AuCl (Scheme 24) [80].…”