Regioselective C–H amination of free base porphyrins via electrogenerated pyridinium-porphyrins and stabilization of easily oxidized amino-porphyrins by protonation

Abstract

Four free base aminoporphyrins were synthesized in two steps via regioselective anodic nucleophilic substitution with pyridine followed by ring opening of the electrogenerated pyridinium with piperidine.

Stepwise Oxidative C–C Coupling and/or C–N Fusion of Zn(II) meso-Pyridin-2-ylthio-porphyrins

“…As first evidence that the C−N fusion reaction worked, a new irreversible reduction peak was observed near −0.8/−1.0 V (E pc (R1) = −0.97 V on the CV of Zn-8 + ,PF 6 − , Figure 6). This potential range is typical of pyridinium reduction, 25,27,31,32 in particular for C−N fused porphyrin cations. 23 The MALDI-TOF mass spectrometry 23 This high selectivity lies on the significant potential difference observed for the first oxidations of Ni-8 and Ni-8 + (ca.…”

“…For Zn-6 + ,PF 6 − and Zn-8 + ,PF 6 − , the newly formed C−N bonds measure 1.425(6) (porphyrin 1), 1.423(6) (porphyrin 2), and 1.420(3) Å that are shorter than other unfused C meso − N pyridinium porphyrins (1.458 ≤ d(C meso −N pyridinium ) ≤ 1.500 Å). 97,98,32 The C meso −S distances are 1.764(5) (porphyrin 1), 1.763(5) (porphyrin 2), and 1.756(2) Å. The C meso −S−C pyridine angles measure 106.5(2) (porphyrin 1), 106.3(2) (porphyrin 2), and 106.28(10)°, respectively.…”

Recent advances in electrochemical meso- and β-functionalization of porphyrins and electrografting of diazonium porphyrins

“…As aforementioned for the β-substitution, Devillers and co-workers reported a new regioselective C-H amination of free base porphyrins via electrogenerated pyridiniumporphyrins [36]. The reaction was successfully tested on free base porphine, 2,7,12,17-tetratert-butylporphyrin and 5,15-di-p-tolylporphyrin providing first the meso-pyridinium derivatives (61-85% yield, Scheme 2A) and then the corresponding amino-porphyrins (81-87% yield).…”

“…More recently, inspired by Yoshida and coll. [35], a new pathway towards the synthesis of amino-porphyrins was developped by Devillers and co-workers [36]. Thus 5,10,15,20-tetraphenylporphyrin (H2TPP) was oxidized in presence of a pyridine excess (100 eq.)…”

“…Scheme 2. Functionalization of porphyrin monomers (A, [11,36,38,41,42]); preparation of oligomers (B, [37]); synthesis of copolymers (C, [43][44][45][46][47][48][49][50]).…”