Alkylation of Arenes with Benzylic and Propargylic Alcohols – Classical versus Fancy Catalysts

Abstract

Gold chloride and BF 3 · etherate were tested as Friedel-Crafts catalysts in the propargylation of electron-rich arenes: differences in reactivity of the catalysts can be used to achieve high selectivity either for monoalkylation or for multiple alkylation products. In the case of a macrocyclization towards a heterocalixarene, gold catalysts exhibited a pronounced selectivity, whereas p-toluenesulfonic acid as catalyst opened up a competing pathway to a structural isomer.

Direct Nucleophilic SN1‐Type Reactions of Alcohols

“…Quite interestingly, different selectivity is obtained as a function of the Lewis acid catalyst. [109] Prim and Campagne described the direct amination of benzylic alcohols 1 and 2 with Boc-amine, tosylamine, nitroaniline, and TMSN 3 in the presence of NaAuCl 4 (5 mol-%) as catalyst in CH 2 Cl 2 at room temperature. Generally, the workup of the reaction comprised filtration through a silica pad to give the corresponding benzylic amine in analytically pure form.…”

Reactivity of 3-silyloxy-1,4-enynes: Gold(III)-catalyzed regioselective nucleophilic substitution

“…Dyker and co-workers used AuCl 3 for the efficient propargylation of electron-rich arenes. [11] Further catalytic methodologies [12] for the propargylic substitution take use of ruthenium [13], rhenium [14], bismuth [15], or copper [16] catalysts. Simple Brønsted-acids such as p-toluenesulfonic acid were also found to catalyze the direct substitution of the hydroxyl group in propargylic alcohols [17].…”

Gold(III) Chloride‐Catalyzed Diastereoselective Alkylation Reactions with Chiral Benzylic Acetates

“…This electrophile 7 appears to be one of the synthetically most useful building blocks tested in the earlier series (5,(7)(8)(9)(10)(11), exhibiting a high diastereoselectivity for an otherwise difficult selective b-arylation of a carboxylate. We were delighted to note that the functional group tolerance of the catalyst was perfectly corroborated by these studies as was the previously observed diastereoselectivity.…”

“…Highly effective Lewis acids have been found which catalyze cleanly the reaction of various arenes with alcohols [3] and acetates. [4] The use of gold-A C H T U N G T R E N N U N G (III) chloride [5] for the catalytic Friedel-Crafts alkylation with benzylic acetates as described by Beller et al [6] and with benzylic alcohols as described by Dyker et al [7] is of particular relevance to the present work. [8] Hashmi et al [9] compared the reactivity of AuCl 3 with other catalysts for use in the condensation of carbonyl compounds with electron-rich arenes.…”