1453496-69-9Relevant 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
