We have developed a new method for the substitution of aromatic rings in calixarenes via lithiation of 25, 26, 27, 28-tetrapropoxycalixarenetricarbonylchromium (l∙Cr(CO)3). Since the Cr(CO)3 unit activates the coordinated benzene ring, functional groups (e. g. methyl, formyl, etc.) can be selectively introduced into the Cr(CO)3 complexed benzene ring of cone-l∙Cr(CO)3 and 1, 3-alternate-l-Cr(CO)3 in the yields of 75-96%. We also studied the reactivity of the 1: 2 complex, 1∙2 Cr(CO)3. In the distal isomer two methyl groups were introduced into the p, p-position in 81% yield whereas in the proximal isomer several methylated products were yielded as a mixture. The substitution reaction occurred selectively at the p-position. The high para selectivity was attributed to the structural characteristics of the complexes. Thus, the present study established the novel method for selective introduction of functional gruops into the upper rim of calix[4 jarenes.
All Science Journal Classification (ASJC) codes
- 化学 (全般)