Electric Moments and Transannular Nitrogen-Carbonyl Interaction in Cyclic Aminoketones¹

The Boat Form in Six-Membered Rings.

“…These observations revealed beyond doubt the existence of interaction between XL the lone-pair electrons of nitrogen and the carbonyl group in XXXVIII. A similar interaction has been observed in a number of medium ring compounds (61). Therefore, XXXVIII may be assumed to exist in the boat conformation (XLI).…”

C‐13 chemical shifts of the carbonyl group—VI: Transannular interactions in mesocyclic compounds

“…* -.CO interaction, (6b) and non-interacted, crown forin (7) for X = S,2*4 evidence for a non-interacted, but folded form (6a) for X = O2 and for the strongly interacted form 5 for compound 4. 6 The effect of solvent on the infrared spectrum of 3 (X = S) was interpreted in terms of a shift of equilibrium toward the interacted form in hydrogen-bonding solvents,2 the hydrogen bonding stabilizing the polarity induced by the transannular interaction.…”

How applicable are geometrical criteria for analysis of the intramolecular N···C=O interaction in the peri-substituted naphthalene system?

“…Through space interactions between the tertiary amino and carbonyl groups in cyclic azaketones were first described in the 1950s. 1 Since then, the transannular N•••CO interaction has been found in a number of other bifunctional molecules including peri-substituted naphthalene systems. 2 Taking into account that with decreasing the N•••C distance the carbon atom becomes increasingly pyramidal, Bürgi, Dunitz and Schefter 3 proposed that such structures may be used for mapping nucleophilic addition reactions of the amine nitrogen to the carbonyl carbon atom of ketones.…”