Competing ring-photoisomerization pathways in the 1,2,4-oxadiazole series. An unprecedented ring-degenerate photoisomerization.
The irradiation of some 5-alkyl-3-amino-1,2,4-oxadiazoles at lambda = 254 nm in methanol in the presence of triethylamine (TEA) gave ring-photoisomerization both into 2-alkyl-5-amino-1,3,4-oxadiazoles and, unprecedently, into the ring-degenerate 3-alkyl-5-amino-1,2,4-oxadiazoles. The competing ring contraction-ring expansion route and the internal cyclization-isomerization mechanism explain the results.
Buscemi
Silvestre
S
Dipartimento di Chimica Organica E. Paternò, Università degli Studi di Palermo, Viale delle Scienze-Parco d'Orleans II, I-90128 Palermo, Italy.
Pace
Andrea
A
Pibiri
Ivana
I
Vivona
Nicolò
N