82849-69-2Relevant academic research and scientific papers
THERMAL CONVERSION OF 1,5,9-TRIYNES. CYCLOADDITIONS OR SIGMATROPIC SHIFTS?
Dower, William V.,Vollhardt, K. Peter C.
, p. 1873 - 1882 (1986)
The gas phase pyrolyses of variously labeled 1,5,9-decatriynes (1) and 1,5,9-cyclododecatriynes (2) were investigated to determine possible modes of thermal isomerizations.Conditions included temperatures in the range 400-600 deg C, pressures of 40 -10E-4 Torr, and contact times of ca 1 ms to 15 s.The labeling patterns in 1 and 2 were chosen such as to be able to distinguish direct intramolecular cycloadditions of the alkyne units to form an aromatic ring (perhaps with subsequent rearrangements), and sigmatropic shifts of the 1,5-diyne moieties.Methods for synthesizing the isotopically (particularly (13)C) labeled triynes were devised and implemented.The route to 5,6-(13)C2-1,5,9-decatriyne (1c) made use of a new procedure for the synthesis of symmetrically disubstituted alkynes involving coupling between two equivalents of an alkyl copper reagent and diiodoacetylene-(13)C2.The synthesis of 1,10-(13)C2-1,5,9-cyclododecatriyne (2b) was accomplished starting with K(13)CN, elaboration to labeled diethyl succinate, a crucial bis-Wittig condensation to labeled 1,5,9-cyclododecatriene 10, and bromination-dehydrobromination of the latter (NaOH-ethylene glycol).Products from the pyrolysis of unlabeled 1a included dicyclobutabenzene, naphtalene and 3,4-dimethylidene-1-(but-3-ynyl)cyclobutene.Pyrolysis of 1b gave 3,6-dideuteriodicyclobutabenzene and partially deuterated naphthalene, that of 1c produced 1,2-(13)C2-dicyclobutabenzene and 9,10-(13)C2-naphthalene.While the pyrolysis of 2a resulted in hexamethylidenecyclohexane (hexaradialene), 2b furnished 1,4-(13)C2-hexaradialene.The results rule out the occurence of cycloadditions of the alkyne units, but are consistent with the intervention of a series sigmatropic shifts which connect starting materials with products.
