e.g. Filippa Pettersson or Cancer Res. 75(6) , 1102-12, (2015) or 10.1002/anie.201600521
Tetrahedron letters
Ethynyl ortho esters as precursors of propargyl cations: The low-temperature, ionic diels-alder addition of ethyl propiolate to 1, 3-dienes via ethynyl ortho esters
PG Gassman, SP Chavan
Index: Gassman, Paul G.; Chavan, Subhash P. Tetrahedron Letters, 1988 , vol. 29, # 28 p. 3407 - 3410
Abstract 3, 3, 3-Triethoxypropyne (triethyl orthopropiolate) was added to a series of 1, 3- dienes at low temperature in the presence of trimethylsilyl inflate to yield the 4π+ 2π products of the formal addition of ethyl propiolate to the 1, 3-dienes.