摘要
ABC-Type subporphyrins 5a-5h, which bear three different meso-aryl substituents, were rationally synthesized by condensation of AB-type tripyrranes and aroyl chlorides. ABC-Type subporphyrins 5i and 5j were synthesized by Pd-catalyzed amination reaction of 4-bromophenyl subporphyrins 5e and 5h, respectively. Comparative studies on these ABC-type subporphyrins with A(3)-type subporphyrins and A(2)B-type subporphyrins revealed that substituent effects are mostly simple superpositions of individual substituents but cooperative effects are recognized for subporphyrins which bear both electron-donating and electron-withdrawing substituents. Despite extensive attempts, enantiomeric separation of B-methoxy ABC-type subporphyrins was unsuccessful, whereas B-phenylated ABC-type subporphyrins were separated to pure enantiomers. Separated enantiomers showed weak but distinct CD signals reflecting the chiral clockwise/anticlockwise arrangements of the meso-aryl substituents. These results suggest facile racemization through S(N)1-type heterolysis of the B-OMe bond in solution.
- 出版日期2014-7