Studies in the Structure of Colchicine. An Infrared Study of Colchicine Derivatives and Related Compounds^1,2

Colchiceine Complexes with Lithium, Sodium and Potassium Salts − Spectroscopic Studies

“…It was supposed that in the tropolone ring C, the active hydrogen was statically located between the two oxygen atoms (on hydroxyl and carbonyl group) in such a way that the resonance was possible without zwitterion formation by shifts of the double bond and OH bonds as indicated. [33] The FT-IR spectra of colchiceine complexes 3-8 show the bands assigned to the stretching vibrations of amine group and hydroxyl group in the region of 3650-2500 cm −1 . These bands are shifted towards higher wavenumbers in comparison to their position in the spectrum of 2, which is a result of the presence of water molecules in the crystalline structure of colchiceine complexes 3-8.…”

Tropones and Tropolones

“…A strong maximum is invariably found between 1600 and 1650 cm.-1 This has been regarded as due to the carbonyl group; its exceptionally low wave number (i.e., high wave length) is regarded as the result of the high degree of conjugation, of the high polarity, and of ring strain, all of which should shift the maximum in this direction. The following positions which have been recorded for several tropone derivatives and three other seven-membered ring ketones invite comparison: (399) 1638 (93) 1625 (96) 1615 (192) 1600 (214) 1595 (192) The significant shift of this absorption by ca. 30 cmy1 towards even lower frequency for tropolone as compared to 3-hydroxytropone must be due largely to hydrogen bonding, which is demonstrated much more clearly by the low frequency of the hydroxyl absorption.…”

“…(b) The infrared spectra The infrared spectra have been investigated and discussed extensively (12,192,194,399,437), with emphasis on the carbonyl and hydroxyl bands. In the tables of compounds in subsequent sections, the papers containing spectra are marked accordingly.…”

Heterocyclic Studies. XIV. Some Further Rearrangements in the Dihydro-1,2-diazepinone Series*,1,2

“…The reaction is presumed to occur via the extended enolate anion 15 which undergoes /3-elimination to the acyclic intermediate 16 followed by cyclization to the aromatic system. Experimental15 1,4-Dimethyl-S-phenyl-l ,6-dihydropyridazine-3-carboxaldehyde (8).-A suspension of 535 mg. of the diazepinone 4s in 8.0 ml. of 6 A hydrochloric acid was warmed to 65^-70°.…”