Butatrien durch Thermolyse von Propiolsaeure-(2-propinyl)ester

Article abstract of DOI:10.1002/hlca.19830660743

Flow thermolysis of 2-propynyl propiolate (5) at 580 deg C afforded butatriene (6) (ca. 50percent) and as by-products, 4-methylene-2-cyclobuten-1-one (7), 2-ethynylpropenal (8), 1-penten-4-yn-3-one (9), 4-penten-2-ynal (10) (tottal ca. 10percent), along with some propynal, acetylene, CO2 and CO.In the same way, propiolic acid (1,1-D2)-2-propynyl propiolate (11) led to (1,1-D2)-butatriene (12) and a litle 4-((D2)methylene)-2-cyclobuten-1-one (13).A mechanism is proposed for the transformation of 5 into 6 and of 11 into 12, which also accounts for the formation of 7, 8, 9 and 10, as well as 13.The position of one of the published 13C-NMR signal of butatriene (6) must be revised.Thermolysis of methyl-(1) and ethyl propiolate (2) resulted in small yields of 2-buten-4-olide (3) and 2-penten-4-olide (4).