Quantum chemical calculations indicate that the kinetic stability of an earlier proposed elegant planar ‘triangular’ benzene dication is very low. The kinetic stability of its methylated derivative ...is even lower.
Quantum chemical calculations indicate that the kinetic stability of an earlier proposed elegant planar ‘triangular’ benzene dication
1a is very low. The kinetic stability of its methylated derivative
2a is even lower.
3b,4-
exo
,4a,5-Tetramethyl-3b,4,4a,5-tetrahydro-4
H
-cyclopropa
a
phenalen-5-yl cation and its
endo
-epimer were proved by NMR method to belong to a new kind of homoaromatic systems: homophenalenyl ...carbocations.
A strong temperature dependence was observed of chemical shifts in the
13
C NMR spectra of 3b,4-
exo
-4a,5-tetramethyl-3b,4,4a,5-tetrahydro-4
H
-cyclopropa
a
phenalen-5-yl cation and its
endo
-epimer ...revealing their stereochemical nonrigidity.
The reactions of (+)‐car‐2‐ene (1) and (+)‐car‐3‐ene (2) with aldehydes in the presence of montmorillonite clay were studied for the first time (Schemes 3 and 5). The major products of these ...reactions are optically active, substituted hexahydroisobenzofurans, probably formed as a result of an attack of the protonated aldehyde at the cyclopropane ring. Quite unexpectedly, the products are cis‐configured at the ring‐fusion site; the fact was established by means of quantum‐chemical calculations and NMR data. It appeared that the behavior of the 2 : 3 mixture 1/2 in reactions with aldehydes in the presence of K10 clay differed substantially from the reactivities of the corresponding individual monoterpenes.
