Gold‐ and Silver‐Catalyzed Reactions of Propargylic Alcohols in the Presence of Protic Additives

Abstract

A wide range of primary, secondary and tertiary propargylic alcohols undergo a Meyer-Schuster rearrangement to give enones at room temperature in the presence of a gold(I) catalyst and small quantities of MeOH or 4-methoxyphenylboronic acid. The syntheses of the enone natural products isoegomaketone and daphenone were achieved using this reaction as the key step. The rearrangement of primary propargylic alcohols can readily be combined in a one-pot procedure with the addition of a nucleophile to the resulting terminal enone, to give β-aryl, β-alkoxy, β-amino or β-sulfido ketones. Propargylic alcohols bearing an adjacent electron-rich aryl group can also undergo silver-catalyzed substitution of the alcohol with oxygen, nitrogen and carbon nucleophiles. This latter reaction was initially observed with a batch of gold catalyst that was probably contaminated with small quantities of silver salt.

Synthesis, Characterization, and Catalytic Activity of Cationic NHC Gold(III) Pyridine Complexes

“…TLC: R f 0.63 (EA/cyclohexane 40%). 1 1-(Hex-1-yn-1-yl)cycloheptanol (12) (ref 39). To a solution of n BuLi (1.6 M in hexanes, 6.1 mmol) in THF (10 mL) was added 1-hexyne (6.1 mmol) at −78°C under argon.…”

Gold‐Catalyzed Migrations and Ring Expansions

“…Interestingly, α,β-unsaturated amides and esters could also be obtained with this method. The reaction was later reported in the absence of molybdenum 104 . More stabilized gold(I) catalysts such as IPrAuCl/AgSbF 6 can also promote the Meyer-Schuster reaction 105 .…”

Complexity-generating hydration reactions via gold-catalyzed addition of boronic acids to alkynes

“…Whilst there are numerous reports of the Au-catalyzed Meyer-Schuster rearrangement of propargylic alcohols [44][45][46][47][48][49], many of these reactions are carried out in MeOH as solvent and require heating for prolonged periods. Under our optimized conditions, the rearrangement of a wide range of propargylic alcohols 46 could be achieved at room temperature using 2 mol % Au catalyst in toluene, in the presence of either 20 mol % of boronic acid 43 or 1 equiv of MeOH as an additive (Scheme 11) [43,50].…”

“…Interestingly, the boronic acid appears to accelerate isomerization of the enone to the more stable isomer. Upon addition of boronic acid 43 to a rearrangement reaction carried out with MeOH as the additive, the (E:Z) ratio of the enone product 47j increased over the course of 6 h from 3:1 to 30:1 (Scheme 12) [50].…”