Strained cyclic molecules. I. The crystal and molecular structure of trans-3-tert-butyl-4-cyanocyclohexanone: a twist conformation

An axialtert-butyl group in strained cyclohexene: X-ray analysis and theoretical calculations of 2-(2-tert-butylcyclohex-3-enyl)propan-2-ol

“…Thus, we have shown that cis-2-tert-butylcyanocyclohexane is more stable than its trans isomer by 1.5 kcal mol À1 (Aycard & Bodot, 1973) (1 kcal mol À1 = 4.184 kJ mol À1 ). For cyclohexanones Viani et al, 1978) and trans-3-tert-butyl-4-X-cyclohexenes in solution, large conformational heterogeneities have been detected and the existence of a pseudo-axial tert-butyl has been postulated (Aycard & Bodot, 1975;Lafrance et al, 1977;Bouteiller-Prati et al, 1976). X-ray analysis of a series of congested 3-tert-butyl-4-X-cyclohexene derivatives (X = CN or CO 2 CH 3 ) has shown that trans stereoisomers exhibit a sofa conformation which is expected to be only 0.8 kcal mol À1 higher than for the half-chair conformation (Bucourt, 1974) with a pseudo-equatorial tert-butyl group (Viani et al, 1978;Cossu et al, 1981).…”

“…We can see that the absolute value of the torsion angle È 23 [À6.6 (2) ] is smaller than the half-chair value. In fact, the ring has a quasi-pure sofa conformation with a minor twisting of the double bond [À2.8 (3) ], as observed in other trans stereoisomers of 3-tert-butyl-4-X-cyclohexene derivatives (Viani et al, 1978(Viani et al, , 1981. Atoms C1±C4/C6 are coplanar to within 0.06 A Ê .…”

Structure et réactivité. III., Evolutions stéréochimiques et chemins réactionnels des radicaux cyclohexyles substitués en 2 et cyclohexényles substitués en 3 (réaction de Kochi)

“…1). La structure du deuxieme conformere n'a pas Ct C prouvCe mais elle est tr&s raisonnable compte tenu des donnkes rtcentes (17). Un calcul analogue au prCctdent permet d'acctder aux differences d'enthalpie libre entre Ctats de transition.…”

Di-tert-butyl-3,5 cyclohexanone-trans

“…ph6nom+ne a d6jh 6t6 observ6 pour d'autres compos6s cyclohexaniques substitu6es en position 3 par un groupement tert-butyle (Viani, Lapasset, Aycard, Lafrance & Bodot, 1978;Lectard, 1976). En se r6f6rant aux Figs.…”