Dimerization McMurry-type

The synthesis of the dioxaporphycene 3.49 has also been reported by Vogel and coworkers. To prepare this new derivative, the mixed furan-pyrrole dialdehyde 3.46 was subject to reductive McMurry-type dimerization. This afforded the air-stable intermediate 3.47 free of isomeric species such as 3.48. Accordingly, oxidation, effected by treating with concentrated nitric acid and 70% perchloric acid, afforded the dioxaporphycene salt 3.49 in 94% yield (based on 3.47) (Scheme 3.1.7). As in the case of the tetraoxaporphycene 3.45 above, H NMR and UV-vis spectroscopic analyses supported the contention that this new dioxaporphycene derivative (shown in its diprotonated form as structure 3.49) is aromatic. 

The stretched porphycene 4.142 ([26]-porphyrin-(6.0.6.0)) was also recently reported by Vogel, et al. This macrocycle was prepared in 50% yield via a McMurry-type dimerization of dialdehyde 4.140, followed by a spontaneous dehydrogenation of the presumed non-aromatic intermediate (Scheme 4.3.11). The free-base form of [26]-porphyrin-(6.0.6.0) (4.142a) proved to be rather fluctional in a variety of solvents over the temperature range of 25 to -50 °C. This hindered... 

The octaethyl-derivative of [24]tetrathiaporphyrin-(2.2.2.2) has also been prepared via two differing synthetic routes." In the first of these, 3,4-diethyl-2,5-thio-phenedicarboxaldehyde 4.170 was cyclo-condensed under reductive McMurry-type conditions to afford 4.171 in 0.3% yield (Scheme 4.4.8). The other approach involved the reductive carbonyl dimerization of the diformyl dithiophenylethene 4.172 to afford macrocycle 4.171 in 0.6% yield. ... 

---