A non-tetradecarboxylative synthesis of 2,7,12,17-tetraphenylporphycene

Abstract

ABSTRACT:A new synthetic method for 2,7,12,17-tetraphenylporphycene (2e, TPPo) which avoids tetradecarboxylation by sublimation of the intermediate tetracarboxylic acid 8 is reported. Thus, the use of a pyrrol 13a bearing two orthogonal ester groups allows the synthesis of bipyrrol 12a, from which the benzyl ester groups are selectively removed to afford diester 11. The latter is transformed to dialdehyde 10 by using the McFayden-Stevens reaction, thus avoiding the unstable bipyrrol 9 formed during the tetradecarboxylation of 8.

Porphycenes: Facts and Prospects in Photodynamic Therapy of Cancer

“…Two main strategies (Scheme 1) have been devised to obtain the precursor 5,5'-diacyl substituted 2,2'-bipyrroles (2): acylation (Y=alkyl group) [85,123] (or formylation, Y=H) [62,66,124,125] of an adequately 4,4'-disubstituted or 3,3',4,4'-tetrasubstituted 2,2'-bipyrrole (3 or 4, respectively), in one side, or transformation of 2,2'-bypyrroles bearing two latent formyl groups to aldehydes 2 (Y=H), two ester groups in the case of 5 [126] or two 4,4,6-trimethyl-1,3-dioxan-2-yl groups in the case of 6 (G=C 7 H 13 O 2 ), on the other side [127].…”

“…The first example of such approach was the synthesis of 2,7,12,17-tetraphenylporphycene 1 (R 1 =Ph, R 2 =Y=H) [126] (Scheme 1) starting from a iodopyrrole (10) bearing two orthogonal ester groups (R 1 =Ph, G=CO 2 Et, R 2 =CO 2 Bn, Z=H), which was transformed to the corresponding bipyrrole 8 (R 1 =Ph, G=CO 2 Et, R 2 =CO 2 Bn, Z=H). The benzyl ester groups were selectively removed to afford diacid 11 (R 1 =Ph) that was subsequently decarboxylated to diester 5 (R 1 =Ph).…”

“…This feature forces bulky metal ions out of the macrocycle plane. The electron lone pairs are not oriented towards the centre of the molecule and therefore, the ability of porphycenes to form metallo- azaporphycenes, is beyond the scope of this review, though the interested reader may want to refer to the original literature [63,99,110,121,124,126,165,[167][168][169][170][171].…”

Palladium(0) catalyzed 2,2′-bipyrrole syntheses

“…They are also well-known common components in molecular recognition and self-assembly processes [1]. Recently, bipyrrole-containing macrocycles have attracted increased attention as therapeutic agents in combination with visible light for the treatment of tumors, especially in connection with extended pyrrole systems [2] such as porphycenes [3, 4] and sapphyrins [5]. However, a key potential synthetic precursor for these compounds, namely 2,2′-bipyrroles, have only limited synthetic methods available [4–7].…”

2,7,12,17‐Tetra(p‐butylphenyl)‐3,6,13,16‐tetraazaporphycene: The First Example of a Straightforward Synthetic Approach to a New Class of Photosensitizing Macrocycles

“…This is particularly true for arylsubstituted porphycenes. [11,12] Moreover, whenever new substituents need to be introduced -in order to modulate properties such as solubility, absorption spectra or redox potential -more often than not a de novo synthesis needs to be developed. When taken together, these are the main reasons precluding the use of combinatorial chemistry techniques for the development of novel photosensitizers.…”