An electron spin resonance study of pentenynyl and pentadiynyl radicals

Synthesis of N-unsubstituted 1,2,3-triazoles via a cascade including propargyl azides, allenyl azides, and triazafulvenes

“…The starting compounds 2w,bb, 55 and 2dd 56 were described in literature and prepared by simple treatment of the corresponding bromides or mesylates with sodium azide. Similarly, the azide 2v was available from the appropriate and known 57 mesylate, whereas 2x was synthesized from hexa-4,5-dien-2-yn-1-ol 58 and phosphorus tribromide followed by the reaction of the resulting propargyl bromide with sodium azide. 59 The amine 2y was accessible by treating 4-chlorobut-2-yn-1-ylamine hydrochloride 60 with an excess of sodium azide.…”

ESR studies of acyclic delocalised radicals

“…The hfs of H 5 is much less than that of H I in propynyl radicals and altogether the pattern of spin distribution is consistent with the idea that triple bonds transmit spin density less effectively than double bonds. The ltrimethylsiloxy derivatives of 39 and 40 have been observed [115] and also the pentenynyl radical obtained on H-abstraction from methyl octadeca-9E-en-12-ynoate [18].…”

“…The hfs (Table VII) illustrate conformers were indistinguishable by ESR spectroscopy, although anomalous temperature dependencies in the hfs of the radical may be an indication of the presence of both [115].…”

“…A useful procedure is to obtain optim~ geometries for the radical in question by the MINDO/3 and UMNDO procedures and then use them in INIX) calculations of spin densities. [124,130,115], propynyl [115], pentadienyl [131,115,132], pentenynyl [115], and pentadiynyl radicals [115]. ~¢DO or U~[NXX) calculations have been reported for allyl [126,131], pentadienyl [131] and propynyl radicals [102].…”

“…For conversion of the barriers to rotation in l-cyanoallyl radicals [94] and pent-2-en-4-ynyl radicals [115] Table X. B. Variation of stabilisation energies with the extent of delocalisation…”