20
J. Oliver–Meseguer and A. Leyva–Pérez
Fig. 1.18 a Phenol synthesis catalyzed by AuCl 3 (0.4 mol%). b Yield time plot for the phenol
synthesis showed in scheme A above (c) and percentage of 3–4 atom Au clusters in solution
according to MALDI–TOF MS measurements (a). The inset shows a magnification of the induction
period when clusters formed. c Scheme for phenol synthesis by using AuCl as a catalyst in submolar amounts under two different reaction conditions (Fig. from Ref. [53]. Copyright © 2013 by
John Wiley & Sons, Inc.)
α carbons to carbonyl groups with alkynes, whereas AuCl 3 was a very unselective catalyst, and only 30% of the cyclopentane product was obtained with a higher
loading (10 mol%) of the Au salt after complete conversion [33]. Upon lowering the
amount of AuCl and AuCl 3 to 0.02 mol%, no conversion was observed (Fig. 1.19)
[53], but under acidic conditions (0.2 mol% of HOTf), the corresponding Au 3–6
clusters are formed to catalyze the reaction with similar results as AuPPh 3 OTf.
1.3.2 Carbon–Heteroatom Bond-Forming Reactions
1.3.2.1 (Ester-Assisted) Hydration of Alkynes (C–O)
This reaction is the first example of catalysis by Au clusters formed in solution, as
far as we know [49]. It can also be employed as a catalytic test to prove the presence
of Au 3–5 clusters since the reaction only proceeds when the Au clusters are present in
J. Oliver–Meseguer and A. Leyva–Pérez
Fig. 1.18 a Phenol synthesis catalyzed by AuCl 3 (0.4 mol%). b Yield time plot for the phenol
synthesis showed in scheme A above (c) and percentage of 3–4 atom Au clusters in solution
according to MALDI–TOF MS measurements (a). The inset shows a magnification of the induction
period when clusters formed. c Scheme for phenol synthesis by using AuCl as a catalyst in submolar amounts under two different reaction conditions (Fig. from Ref. [53]. Copyright © 2013 by
John Wiley & Sons, Inc.)
α carbons to carbonyl groups with alkynes, whereas AuCl 3 was a very unselective catalyst, and only 30% of the cyclopentane product was obtained with a higher
loading (10 mol%) of the Au salt after complete conversion [33]. Upon lowering the
amount of AuCl and AuCl 3 to 0.02 mol%, no conversion was observed (Fig. 1.19)
[53], but under acidic conditions (0.2 mol% of HOTf), the corresponding Au 3–6
clusters are formed to catalyze the reaction with similar results as AuPPh 3 OTf.
1.3.2 Carbon–Heteroatom Bond-Forming Reactions
1.3.2.1 (Ester-Assisted) Hydration of Alkynes (C–O)
This reaction is the first example of catalysis by Au clusters formed in solution, as
far as we know [49]. It can also be employed as a catalytic test to prove the presence
of Au 3–5 clusters since the reaction only proceeds when the Au clusters are present in