The author of ãReactions of alkyl 4-hydroxybut-2-ynoates with arenes under superelectrophilic activation with triflic acid or HUSY zeolite: Alternative propargylation or allenylation of arenes, and synthesis of furan-2-onesã?were Devleshova, Natalia A.; Lozovskiy, Stanislav V.; Vasilyev, Aleksander V.. And the article was published in Tetrahedron in 2019. Safety of Ethyl propiolate The author mentioned the following in the article:
Reactions of alkyl 4-aryl(or 4,4-diaryl)-4-hydroxybut-2-ynoates [Ar(H or Ar’)(OH)C4-C3â¡C2-CO2Alk], (Ar = Ar’ = Ph, 4-MeC6H4, 4-MeOC6H4, 4-BrC6H4, etc.; Alk = Me, Et) with arenes under the action of triflic acid TfOH or HUSY zeolite result in the formation of two main compounds, aryl substituted furan-2-ones I (Ar1 = Ar2 = Ph, 4-MeC6H4, 4-MeOC6H4, 4-BrC6H4, etc.; Ar3 = 2,5-di-MeC6H3, 3,4-di-MeC6H3, 3-F,4-MeC6H3, etc.) or products of propargylation II (Ar1 = Ph, 4-MeC6H4, 4-MeOC6H4, 4-BrC6H4, etc.; Ar3 = 2,5-di-MeC6H3, 3,4-di-MeC6H3, 3-F,4-MeC6H3, etc.; Alk = Me, Et) of electron rich arenes. Key reactive intermediates in these transformations are the corresponding O,O-diprotonated forms of starting butynoates, Ar(H or Ar’)(+OH2)C4-C3â¡C2-C(=O+H)(OAlk), dehydration of which gives rise to mesomeric propargyl-allenyl cations Ar(H or Ar’)(OH)4C+-C3â¡C2-C(=O+H)(OAlk) â?Ar(H or Ar’)(OH)4C = C3 = 2C+-C(=O+H)(OAlk), having two electrophilic centers on the carbons C4 and C2 resp. Reactions of these species with arenes at C4 lead to products of arene propargylation, alternatively, reactions at C2 result in allenylation of arenes, followed by further transformation into furan-2-ones. Using quantum chem. calculations by the DFT method, it has been shown that the reactivity of such propargyl-allenyl cations is mainly explained by orbital factors. Plausible reaction mechanism is discussed.Ethyl propiolate(cas: 623-47-2Safety of Ethyl propiolate) was used in this study.
Ethyl propiolate(cas: 623-47-2) is a clear colorless to pale yellow liquid that is soluble in ethanol, ether and chloroform. It an important organic chemical raw material and pharmaceutical intermediate. Ethyl propargylate is obtained by oxidation of propargyl alcohol to propargylic acid followed by esterification.Safety of Ethyl propiolate
Referemce:
Ester – Wikipedia,
Ester – an overview | ScienceDirect Topics