The 2,6-dimercaptoazulene motif: efficient synthesis and completely regioselective metallation of its 6-mercapto terminus

Abstract

2,6-Dimercapto-1,3-diethoxycarbonylazulene, a rare example of an unsymmetrical dimercaptoarene, was efficiently synthesized via two routes from common azulenic precursors. The SH-termini of this linear nonbenzenoid dimercaptan exhibit markedly different acidities, which permitted exclusively regioselective metallation of its 6-SH end with the [PPh₃PAu^I] fragment to afford the only mononuclear adduct (10) of a dimercaptoarene known to date. Subsequent metallation of the 2-SH terminus of 10 with another equivalent of [PPh₃PAu^I] gave the corresponding dinuclear Au^I complex featuring the 2,6-azulenedithiolate linker. The complex constitutes a unique unsymmetrical platform for probing the exchange of gold-bound thiolates within a single compound.