Stereoselective gold(I)-catalyzed intermolecular hydroalkoxlation of alkynes
(Chemical Equation Presented) We report the use of cationic gold complexes [Au(NHC)(CH3CN)][BF4] and [{Au(NHC)}2(μ-OH)][BF4] (NHC = N-heterocyclic carbene) as highly active catalysts in the solvent-free hydroalkoxylation of internal alkynes using primary and secondary alcohols. Using this simple protocol, a broad range of (Z)-vinyl ethers were obtained in excellent yields and high stereoselectivities. The methodology allows for the use of catalyst loadings as low as 200 ppm for the addition of primary alcohols to internal alkynes (TON = 35 000, TOF = 2188 h-1).
Veenboer, Richard M. P.,Dupuy, Stphanie,Nolan, Steven P.
Chemistry of O-Alkyl Selenoesters. Reaction with Triethylphosphine
The reaction between triethylphosphine and a number of aliphatic and aromatic selenoesters under oxygen-free conditions have been investigated.The purple intermediate formed in the reaction with the aliphatic selenoesters was quenched with atmospheric oxygen and gave the corresponding esters, whereas quenching with methyl iodide gave the corresponding 1-alkoxy-1-iodoalkyltriethylphosphonium iodides (13)-(16).The 1-alkoxy-1-iodoalkyltriethylphosphonium iodides gave the 1-alkoxyalkyltriethylphosphonium iodides (17)-(20) upon treatment with methanol, and treatment with benzaldehyde at -70 deg C gave α-alkoxyalkyl phenyl ketones (22)-(25).The reaction between the selenobenzoates and triethylphosphine gave α-dialkoxy-stilbenes and -dibenzyls.When the reaction was carried out in cyclohexene 7-alkoxy-7-phenylbicycloheptanes were formed.The presence of benzaldehyde in the reaction mixture led to α-alkoxystilbenes.An explanation for these different reactions is presented.
Hansen, Per-Egil
p. 1627 - 1634
(2007/10/02)
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