Synthesis of New Amino-Functionalized Porphyrins:Preliminary Study of Their Organophotocatalytic Activity

Abstract

The design, synthesis, and initial study of amino-functionalized porphyrins as a new class of bifunctional catalysts for asymmetric organophotocatalysis is described. Two new types of amine–porphyrin hybrids derived from 5,10,15,20-tetraphenylporphyrin (TPPH2), in which a cyclic secondary amine moiety is covalently linked either to a b-pyrrolic position (Type A) or to the p-position of one of the meso phenyl groups (Type B), were prepared by condensation, reductive amination, or amidation reactions from the suitable porphyrins (either formyl or methanamine derivatives) with readily available chiral amines. A preliminary study of the possible use of Type A amine–porphyrin hybrids as asymmetric, bifunctional organophotocatalysts was performed using the chiral, imidazolidinone-catalyzed Diels–Alder cycloaddition between cyclopentadiene 28 and trans-cinnamaldehyde 29 as a benchmark reaction. The yield and the stereochemical outcome of this process, obtained under purely organocatalytic conditions, under dual organophocatalysis, and under bifunctional organophotocatalysis, were compared.

Substituent Effects in the Photophysical and Electrochemical Properties of meso-Tetraphenylporphyrin Derivatives

“…The 5-(4'-benzoyl)-10,15,20-triphenylporphyrin 6 was easily obtained in two steps from the known [11] 5-(4'-formyl) derivative 10 (Scheme 1). Treatment of this compound with an excess of phenylmagnesium bromide in anhydrous THF produced the benzhydryl alcohol 11, that was subsequently oxidized by pyridinium chlorochromate to provide 6 in 63% overall yield, after chromatographic purification.…”

“…Treatment of this compound with an excess of phenylmagnesium bromide in anhydrous THF produced the benzhydryl alcohol 11, that was subsequently oxidized by pyridinium chlorochromate to provide 6 in 63% overall yield, after chromatographic purification. On the other hand, phenyl(5,10,15,20-tetraphenylporphyrin-7-yl)methanone 7 could be accessed either from the -formyl derivative 4 [11,20] or from the corresponding Cu-complex 5 [11,21] (Scheme 2). As in the case of 6 above, the -benzoyl derivative 7 was synthesized through addition of the phenyl Grignard reagent, and the resulting alcohol 12 was oxidized with PCC.…”

“…13 A 1M THF solution of phenylmagnesium bromide (1.4 mL, 1.4 mmol, 5 equiv.) was added dropwise to a flask containing a cold (-78ºC., dry-ice/acetone bath) solution of the known [11,20] 2formyl-5,10,15,20-tetraphenylporphyrin 4 (183 mg, 0.28 mmol) in anhydrous THF (60 mL) under an argon atmosphere. The reaction was allowed to warm up to room temperature and stirred for 4 h, at which time it was carefully quenched with 5 mL of aq.…”

“…In the context of our research in the use of porphyrins as macromolecular catalysts [9] and as switchable organocatalysts [10], we have been recently interested in the photocatalytic activity of functionalized porphyrins [11]. While several studies have been performed concerning the redox electrochemical behaviour of metalloporphyrins [12,13], much less quantitative data are available on the photophysical and electrochemical properties of free-base porphyrins [7,8,14,15], and a systematic study on the effect of the electronic nature and of the position of the substituents on both the ground-state and the excited-state redox potentials of these compounds is still lacking.…”

Synthesis, Characterization, X-ray Molecular Structure, Antioxidant, Antifungal and Allelopathic Activity of a new Isonicotinate-derived meso-Tetraarylporphyrin

“…The presence of porphyrins in myriad biological systems, coupled with the ability to finely tune their chemical and physical properties, position both free base porphyrins and metalloporphyrins as adaptable materials and as crucial for scientific investigations. The deep-rooted biological importance of these tetrapyrrolic macrocycles and their exceptional electronic and structural properties have spurred their widespread utilization, encompassing their use as photosensitizers in photodynamic therapy [1,2] and in functionalization reactions [3,4], as sensors [5,6], in solar cells [7,8], and more recently, as organocatalysts [9][10][11][12][13] and as photoredox catalysts [4,14,15]. The availability of a large number of porphyrins and metalloporphyrins in these applications is made possible mainly thanks Disclaimer/Publisher's Note: The statements, opinions, and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s).…”