IS THROUGH-BOND DIHYDROAROMATICITY ATTAINABLE - PREPARATION OF [4,5]DIHOMOTROPONE, INVESTIGATION OF ITS GROUND-STATE PROPERTIES, AND AN ATTEMPT TO GENERATE THE DIHOMOTROPYLIUM CATION
La. Paquette et al., IS THROUGH-BOND DIHYDROAROMATICITY ATTAINABLE - PREPARATION OF [4,5]DIHOMOTROPONE, INVESTIGATION OF ITS GROUND-STATE PROPERTIES, AND AN ATTEMPT TO GENERATE THE DIHOMOTROPYLIUM CATION, Journal of organic chemistry, 59(19), 1994, pp. 5700-5707
Construction of the first dihomotropone (6) has been accomplished. The
key elements of the synthesis were a regiocontrolled expansion of a [
4.1.1] bicyclic cr-bromo ketone and introduction of the dienone double
bonds by means of the Garbisch method. The spectral properties of 6 u
nder neutral and strongly acidic conditions are described and interpre
ted in terms of a lack of dihomoaromatic character. The parent bicyclo
[5.1.1]nonadienyl cation is unstable and experiences ready Wagner-Meer
wein rearrangement to the bicyclo[4.2.1]nonadien-7-yl cation. These fe
atures appear well suited to the ultimate evaluation of through-bond i
nteraction in tricyclic homologues of 6 that carry perpendicular pi ar
rays in the third ring.