1. The Curtius rearrangement in isomeric β- and γ-cycloheptatrienecarboxylic acids and norcaradlenecarboxylic acid was studied. It was shown that rearrangement goes without isomerization of the migrating hydrocarbon radical under the conditions employed. 2. The following were synthesized for the first time: 1,3,5-, 1,3,6- and 2,4,6-cycloheptatrienyl isocyanates, norcaradienyl isocyanates, 1,3,5-, 1,3,6- and 2,4,6-cycloheptatrienyl ureas, norcaradienyl urea, N-phenyl-N′-1,3,5-,-1,3,6-, and -2,4,6-cycloheptatrienyl ureas, and N-phenyl-N′-norcaradienyl urea. 3. The absorption spectra in the near ultraviolet (25,000–50,000 cm−1 of 22 derivatives of cycloheptatriene and norcaradeene were examined. It was shown that in nocaradiene derivatives (IV, R = COON, LOCI, CONH2, NCO) the three-membered ring transmits conjugation in a similar manner to a double bond.