Enediyne isomers of tetraethynylethene.
Three isomers of tetraethynylethene (1, C10H4) have been prepared by palladium-catalyzed Negishi coupling of a trimethylsilylbutadiynyl zinc reagent with a bromoalkene, followed by mild deprotection with potassium carbonate in methanol. The unsubstituted enynes, 3-ethynyloct-3-ene-1,5,7-triyne (2), trans-dec-5-ene-1,3,7,9-tetrayne (3), and cis-dec-5-ene-1,3,7,9-tetrayne (4), exhibit modest stability at -20 degrees C but decompose rapidly at room temperature. Electronic absorption spectra of 2, 3, and 4 reveal a characteristic vibronic progression at 260-320 nm. Spectral features at shorter wavelength discriminate among the isomers, and permit the assignment of 2 and 3 as apparent dimerization products of triplet carbene H-CC-C-CC-H in matrices at low temperature. Computed relative energies of these C10H4 isomers (MP2/6-31G) are 1 (14.0 kcal/mol), 2 (6.8 kcal/mol), 3 (0.0 kcal/mol), and 4 (1.0 kcal/mol).
Bowling
Nathan P
NP
Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, USA.
McMahon
Robert J
RJ
D019281:Dimerization; D053281:Enediynes / Q000138:chemical synthesis / Q000737:chemistry*; D007536:Isomerism; D015394:Molecular Structure; D013053:Spectrophotometry
D053281:Enediynes; C520450:tetraethynylethene