Hashmi phenol synthesis

The resulting NAC-Au(I) chlorides, especially the one prepared from commercial available tert-butyl-isocyanide and diethylamine (R = tert-Butyl = R = Ethyl), were successfully tested in variations of the Hashmi phenol synthesis [14]. Further variations of the synthesis shown in Scheme 9.5 led to NAC-Au(I) chlorides, which can, in their catalytically active form, achieve remarkably high turnover numbers (up to 32000000) in intramolecular addition reactions of hydroxy groups to alkynes [17]. 

The Hashmi phenol synthesis is another example of a perfect atom-economical reaction. Hashmi and coworkers reported this transformation for the first time in 2000, and have been actively working on improving and developing more efficient catalytic processes ever since. As a result of this work, they have reported several extremely active catalytic systems for this transformation. In 2011, they reported TONs of 1900 and 1860 using catalysts VI and VII, respectively, in a comparative study between the use of KITPhos and SPhos ligands in the gold-catalysed phenol synthesis (Scheme 16.14). ... 

Scheme 16.14 Hashmi phenol synthesis catalysed by gold complexes bearing SPhos.

Phenol Synthesis A new method for obtaining arenes from easily available furans was reported by Hashmi et al. [19]. In this first paper, AuCl3 was used to produce a highly substituted phenol without side products. 

In a joint study by Corma and Hashmi, heterogeneous gold catalysts based on nanogold on nanocerium oxide support were employed for phenol synthesis [172]. 

An extension of Hashmi s Au(III)-catalyzed phenol synthesis [81] to furan substrates 9 bearing an additional alkyne moiety allowed the preparation of C6-C7-heterofused benzofuran 11 (Scheme 9.3) [82]. According to the proposed mechanism, the Au(III)-catalyzed arene formation reaction generates o-alkynylphenol 10. A subsequent Au(III)-catalyzed cycloisomerization of the latter, following the general mechanism for an intramolecular nucleophilic addition of heteroatom to transition metal-activated carbon-carbon multiple bonds, gives 11 (Scheme 9.3). 

Scheme 9.21 Optimized conditions for Echavarren s intermolecular applications of the phenol synthesis of Hashmi et al. [40].

Hashmi s group surveyed a modular library of 21 Au-ADC complexes prepared by the isocyanide method in the catalytic phenol synthesis using alkyne-... 

Recently, Hashmi and coworkers reported a selective Diels-Alder synthesis of phenolic compounds catalysed by Au(III) (equation 130). The mechanism has proven to include an intramolecular migration of the oxygen atom of the furan ring. Several other transition metals with d configuration (Pd , Pt , Rh , Ir ) allow this conversion, but Au is shown to be the most active catalyst giving the cleanest conversion. 

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