17O chemical shifts and deuterium isotope effects on 13C chemical shifts of intramolecularly hydrogen-bonded compounds

O-17 chemical shifts were measured in 40 enamines activated in the beta-position by C=O, COO, NO2, SO and SO2 groups. Data for the oxygen-containing series of o-hydroxyacyl aromatics are also included for comparison. Intramolecular hydrogen bonding in the enamines is discussed in terms of the acceptor and donor groups and the separating link. O-17 chemical shifts, the two-bond deuterium isotope shifts on C-alpha C-13 shifts and H-1 NH or OH chemical shifts are correlated to show the interrelations of these parameters in elucidating intramolecular hydrogen bonds and their strength in a wide variety of compounds. O-17 chemical shifts in open-chain compounds are shown to reflect intramolecular hydrogen bonding by a change to lower frequency whereas for five-membered rings steric effects cause higher frequency chemical shifts. (C) 1998 John Wiley & Sons, Ltd.