Gold(III) Triggered Transformations of 22‐Methyl‐m‐benziporphyrin Involving an Effective Contraction of Benzene to Cyclopentadiene

Abstract

A structurally prearranged carbaporphyrin, 22-methyl-m-benziporphyrin, provided the perfect macrocyclic platform to form gold(III) 22-methyl-m-benziporphyrin, which facilitates the specific m-benzene ring contraction yielding gold(III) 21-methyl 21-carbaporphyrin with remarkably high yield.

A meso‐Tetraaryl‐21‐carbaporphyrin: Incorporation of a Cyclopentadiene Unit into a Porphyrin Architecture

“…[16] Ar ational synthesis of the 10,15-dimesityl-21carba-23-thiaporphyrin 6 and a2 1-carba-23-thiaporphyrin dimer with the dihydrofulvalene bridging motif were also elaborated. [19][20][21][22][23][24] Thus 7 has been trapped as am acrocyclic ligand in the course of palladium(II), gold(III), and rhodium(III) benziporphyrin rearrangements involving the facile intramolecular contraction of the embedded benzene into ac yclopentadiene (Scheme 2). Paradoxically,s ome insight into its remarkable coordination/ organometallic chemistry has been provided by exploration of p-benziporphyrin and m-benziporphyrin reactivity.…”

“…[17,18] Incorporation of ac yclopentadiene ring into the archetypal meso-substituted porphyrin pattern is expected to create an original class of meso-tetraaryl-21-carbaporphyrins( 7; Scheme 1), which to date has not been synthesized. [19][20][21][22][23][24] Evidently this approach is far from being general and is hitherto limited to ar ather small number of transition-metal ions.I na ddition, the demetallation of 7-M (M = Pd II ,A u III ,Rh III )t o7 is not feasible. [19][20][21][22][23][24] Thus 7 has been trapped as am acrocyclic ligand in the course of palladium(II), gold(III), and rhodium(III) benziporphyrin rearrangements involving the facile intramolecular contraction of the embedded benzene into ac yclopentadiene (Scheme 2).…”

“…[10,11,25] As apart of our research to explore the reactivity of carbaporphyrinoids, [19][20][21][22][23][24][25] herein we report on the rational synthesis of 7. [10,11,25] As apart of our research to explore the reactivity of carbaporphyrinoids, [19][20][21][22][23][24][25] herein we report on the rational synthesis of 7.…”

Expanded Porphyrin Contraction: From [22]Triphyrin(6.6.0) to [22]Triphyrin(6.5.0)

“…A 1 H NMR‐monitored contraction in heterogeneous conditions (Figure S2, Supporting Information) proceeded very slowly, the reaction required 5 days for completion, and solely the substrate and the product signals were detected. Alumina‐promoted ring contractions of porphyrinoids have been already observed for rhodium(III) and gold(III) complexes of m ‐benziporphyrin to form 21‐carbaporphyrin complexes, and very recently for uranyl(VI) pyrihexaphyrin, yielding another contracted macrocycle . In the reported chemistry the central metal ions played crucial roles.…”

“…Skeletal rearrangements are encountered rather rarely; they may be exemplified by a core heteroatom replacement or extrusion, macrocyclic fusion, and ring expansion or contraction. For porphyrinoid aromatic macrocycles a contraction may take place at both—a meso ‐link or at a cyclic subunit, like a pyrrole in a regular porphyrin, a phenylene ring in benziporphyrin or naphthiporphyrin, or at the outer heptacyclic ring of azuliporphyrinoids as well . The meso ‐link extrusion promoted by rhenium coordination was observed in an electron‐deficient tetrakis(trifluoromethyl)porphyrin .…”