Gold-catalysed reactions, room temperature

In 2006, Gagosz reported the gold-mediated stereoselective synthesis of 2,5-dihydrofurans from butynediol monobenzoates at room temperature. The transformation involved two sequential gold-catalysed reactions the formation of an allene derivative followed by a cyclisation. The reaction was... 

With another change of scene, we note the ability of gold to catalyse transformation of polycyclic hydrocarbons having fascinating structures (Scheme 13.4) 19 the reactions depicted there were catalysed either in the vapour phase using a gold-lined reactor at temperatures between 373 and 543 K and contact times of 10-20 s they were also effected by the complex Au(DCP)2C1 (DCP = dicyclopentadiene) in solution over 1 day at room temperature. 

Krause reported the gold-catalysed cycloisomerisation of functionalised allenes in water at room temperature (Scheme 16.30)7 This reaction was catalysed by 5 mol% of HAuCU and 1 equivalent of lithium chloride was added to prevent catalyst decomposition. The reaction gave access to five- or six-membered ring oxygen or nitrogen heterocycles. The chirality of the starting material was fully transferred to the heterocycle in all the cases. 

One of the principles of Green Chemistiy is the reduction of the energy requirements to perform a reaction, that is, reactions that can be conducted at room temperature are preferred. For this reason, in this section we will discuss relevant examples of gold-catalysed transformations at room temperature. The selected protocols are grouped by transformations. 

Larock reported another protocol for the synthesis of furans at room temperature using 2-(l-allq nyl)-2-alken-l-ones and various nucleophiles to form highly substituted furans (Scheme 16.57). The reaction was catalysed by 1 mol% of gold(m) chloride and proceeded at room temperature, in short... 

Genet, Michelet and coworkers reported the gold-promoted cyclisation of bis homopropargylic diols to afford bicyclic ketals at room temperature. The transformation was catalysed by 2 mol% of gold(i)- or gold(iii)-chloride in methanol and the final products were isolated in very good to excellent yields after short reaction times (Scheme 16.58). 

Nakamura and coworkers reported an intramolecular carbothiolation of allq nes catalysed by gold(i) chloride at room temperature. The protocol allowed for the synthesis of 2,3-disubstituted benzothiophenes in short reaction times, with excellent yields when 2 mol% of the catalyst was used (Scheme 16.62). 

Echavarren reported the cycloisomerisation of 1,7-enynes catalysed hy a cationic gold(i) species at room temperature. The reaction proceeded using 2 mol% of XXXI in dichloromethane. Remarkably, most of the transformations required only 5 min (Scheme 16.68). 

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