F. Fulop et al., SYNTHESIS AND RING-CHAIN TAUTOMERISM OF STEREOISOMERIC 1,3-OXAZINES CONDENSED WITH A TERT-BUTYL-SUBSTITUTED CYCLOPENTANE RING, ACH, models in chemistry, 131(3-4), 1994, pp. 435-443
In contrast with the striking differences observed in the reactivities
and spectroscopic properties of 1,2-difunctional 4-tert-butylcyclopen
tane derivatives and the corresponding compounds containing no tert-bu
tyl substituent, in the ring-chain tautomerism of cyclopentane-fused t
etrahydro-1,3-oxazines the tert-butyl group makes only a small constan
t electronic contribution. The ring-chain equilibria in each series ca
n be characterized by the equation log K-x = p sigma(+) + c.