226895-75-6Relevant academic research and scientific papers
Gold-catalyzed regioselective hydration of propargyl acetates assisted by a neighboring carbonyl group: Access to α-acyloxy methyl ketones and synthesis of (±)-actinopolymorphol B
Ghosh, Nayan,Nayak, Sanatan,Sahoo, Akhila K.
supporting information; experimental part, p. 500 - 511 (2011/04/17)
A general atom-economical approach for the synthesis of α-acyloxy methyl ketone is demonstrated through regioselective hydration of a wide range of propargyl acetates. Readily available catalyst comprising of 1% Ph 3PAuCl and 1% AgSbF6 in dioxane-H2O efficiently hydrolyzes the terminal alkynes of the propargyl acetate in the absence of acid promoters at ambient temperature within a short time. Effective regioselective hydration is facilitated by the neighboring carbonyl group as demonstrated through 18O-labeling study. Compatibility of functional moieties and tolerance to various acid-labile protecting groups are observed. The catalytic condition is also suitable to perform hydration of TMS-substituted propargyl acetates, even though it requires prolonged reaction time for completion. Stereointegrity of the propargylic acetate is preserved during the hydration. The robustness of the system is successfully demonstrated through gram scale preparation of the product in nearly quantitative yield. The common α-acyloxy methyl ketone is transformed to 1,2-diol and 1,2-amino alcohol derivatives. Synthesis of actinopolymorphol B is achieved for the first time involving hydration of the propargyl acetate as the key step.
[(NHC)AuI]-catalyzed formation of conjugated enones and enals: An experimental and computational study
Marion, Nicolas,Carlqvist, Peter,Gealageas, Ronan,De Fremont, Pierre,Maseras, Feliu,Nolan, Steven P.
, p. 6437 - 6451 (2008/02/13)
The [(NHC)AuI]-catalyzed (NHC = N-heterocyclic carbene) formation of α,β-unsaturated carbonyl compounds (enones and enals) from propargylic acetates is described. The reactions occur at 60°C in 8 h in the presence of an equimolar mixture of [(NHC)AuCl] and AgSbF6 and produce conjugated enones and enals in high yields. Optimization studies revealed that the reaction is sensitive to the solvent, the NHC, and, to a lesser extent, to the silver salt employed, leading to the use of [(ItBu)AuCl]/ AgSbF6 in THF as an efficient catalytic system. This transformation proved to have a broad scope, enabling the stereoselective formation of (E)-enones and -enals with great structural diversity. The effect of substitution at the propargylic and acetylenic positions has been investigated, as well as the effect of aryl substitution on the formation of cinnamyl ketones. The presence or absence of water in the reaction mixture was found to be crucial. From the same phenylpropargyl acetates, anhydrous conditions led to the formation of indene compounds via a tandem [3,3] sigmatropic rearrangement/intramolecular hydroarylation process, whereas simply adding water to the reaction mixture produced enone derivatives cleanly. Several mechanistic hypotheses, including the hydrolysis of an allenol ester intermediate and SN2′ addition of water, were examined to gain an insight into this transformation. Mechanistic investigations and computational studies support [(NHC)AuOH], produced in situ from [(NHC)AuSbF6] and H 2O, instead of cationic [(NHC)AuSbF6] as the catalytically active species. Based on DFT calculations performed at the B3LYP level of theory, a full catalytic cycle featuring an unprecedented transfer of the OH moiety bound to the gold center to the C≡C bond leading to the formation of a gold-allenolate is proposed.
