1379804-66-6Relevant academic research and scientific papers
Electrophilic addition of propargylic cations to allenes: Formation of crowded chloro- and azido-enynes by trapping of the resulting allylic cations with TMSX (X = Cl, N3): A synthetic and computational study
Laali, Kenneth K.,Nandi, Ganesh C.,Borosky, Gabriela L.,Kumar, G.G.K.S. Narayana
, p. 5455 - 5463 (2013/09/02)
Propargylic cations, generated by the ionization of propargyl alcohols with catalytic amounts of Bi(OTf)3, react with aryl-substituted allenes to generate incipient allylic cations that are quenched in the presence of TMSCl to form a number of sterically crowded chloro-enynes as a mixture of Z and E isomers with a strong preference for the Z alkenes. Several other metallic triflates, M(OTf)3 (M = Sc, Yb, La), as well as bismuth nitrate Bi(NO3)3·5H2O also promote this reaction with similar conversions and stereoselectivity. Although trapping with TMSBr and TMSI gave intractable mixtures, trapping with TMSN3 in a couple of cases led to the isolation of the corresponding isomeric azido-enynes, albeit in lower isolated yields and lower stereoselectivity. Competitive formation of the Meyer-Schuster rearrangement products was also observed. Sterically crowded chloro-allenes did not form adducts with propargyl alcohols, instead they underwent a skeletal rearrangement under the influence of Bi(OTf)3 to form 2-chloro-butadienes. The results of DFT calculations indicated that the relative anti/syn energies of the propargyl cation and the energy difference between the Z/E isomeric products are too small to explain the stereochemical preference observed for the enynes. A study of the transition state in the crucial C-C bond-forming step by DFT indicated that rotation of the benzylic portion away from the propargyl cation may be a key factor in favoring the anti isomer of the allylic cation. Propargylic cations generated by the ionization of propargylic alcohols with metallic triflates react with aryl-allenes in the presence of TMSCl to form crowded chloro-enynes Copyright
Gold- and silver-catalyzed reactions of propargylic alcohols in the presence of protic additives
Pennell, Matthew N.,Turner, Peter G.,Sheppard, Tom D.
experimental part, p. 4748 - 4758 (2012/05/04)
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.
Triazole-gold-promoted, effective synthesis of enones from propargylic esters and alcohols: A catalyst offering chemoselectivity, acidity and ligand economy
Wang, Dawei,Zhang, Yanwei,Harris, Alexandria,Gautam, Lekh Nath S.,Chen, Yunfeng,Shi, Xiaodong
supporting information; experimental part, p. 2584 - 2588 (2011/12/01)
The air, moisture and thermally stable 1,2,3-triazole coordinated gold(I) complexes (TA-Au) were revealed as the effective catalysts in promoting propargylic ester rearrangement and sequential allene hydration, giving the enones with excellent yields (up to 97% yields, 0.2% loading). The catalysts could also catalyze the more challenging Meyer-Schuster rearrangement (0.5% loading, up to 98% yields). The reported reaction confirmed TA-Au as a chemoselective catalyst in promoting alkyne activation with high efficiency and improved ligand economy. Copyright
