Adaptation of the Rothemund Reaction for Carbaporphyrin Synthesis: Preparation of meso-Tetraphenylazuliporphyrin and Related Benzocarbaporphyrins

Metalation of Carbaporphyrinoid Systems

“…[38,39] Tetraarylazuliporphyrins 44 similarly react with t BuOOH and KOH to give the analogous benzocarbaporphyrins 54, and it is noteworthy that this is currently the only known route to tetraaryl benzocarbaporphyrins. [50,53] In the tetraaryl benzocarbaporphyrin series 54, the signal of the inner CH is still shifted upfield to beyond -5 ppm and the UV-vis spectra are porphyrin-like showing the presence of a strong Soret band and several Q absorptions. [50,53] However, X-ray crystallography shows that the indene unit is significantly tilted from the mean plane of the macrocycle .…”

“…[48] The synthesis of 43 resembles a Rothemund-type porphyrin synthesis, [49] and this lead us to speculate that the same approach might be used to prepare azuliporphyrins 44. [50] Using conditions adapted from Lindsey's methods for preparing tetraarylporphyrins, [51,52] a 1:3:4 molar ratio of azulene, pyrrole and arylaldehydes were stirred with BF 3 . Et 2 O in chloroform for 16 hours.…”

“…Following oxidation with DDQ and column chromatography, the tetraarylazuliporphyrins 44 were isolated in good yields (generally 10-20%). [50,53,54] A similar approach to benziporphyrins was also reported. [55] Benzene dicarbinols 45 were reacted with pyrrole and aromatic aldehydes using catalytic BF 3 ×Et 2 O in dichloromethane to give, following oxidation with DDQ, Figure 2.…”

“…[50,53] In the tetraaryl benzocarbaporphyrin series 54, the signal of the inner CH is still shifted upfield to beyond -5 ppm and the UV-vis spectra are porphyrin-like showing the presence of a strong Soret band and several Q absorptions. [50,53] However, X-ray crystallography shows that the indene unit is significantly tilted from the mean plane of the macrocycle . X-ray crystal structure of tetraphenylbenzocarbaporphyrin 54.…”

Oxidative Metalation of Azuliporphyrins with Copper(II) Salts: Formation of a Porphyrin Analogue System with a Unique Fully Conjugated Nonaromatic Azulene Subunit

“…[8] Our recent studies have focused on the synthesis and chemistry of azuliporphyrins 4 and 5-carbaporphyrinoids that show intermediary aromatic characteristics. [9][10][11][12] Azuliporphyrins react with nickel(ii), palladium(ii), or platinum(ii) salts under mild conditions to afford the corresponding organometallic derivatives (for example, 6-8). [6] We now report that azuliporphyrins 5 give an unusual oxidative metalation with copper(ii) acetate to form a new porphyrinoid ligand system with highly modified spectroscopic properties.…”