A Facile Palladium‐Mediated Contraction of Benzene to Cyclopentadiene: Transformations of Palladium(II) p‐Benziporphyrin

Benziporphyrins, a unique platform for exploring the aromatic characteristics of porphyrinoid systems

“…that the naphthalene subunit is tilted relative to the rest of the macrocycle by 71°and 68°, respectively. 40 Initially, a palladium(II) complex 57 was generated but upon treatment with potassium carbonate a ring contraction reaction took place affording palladium(II) carbaporphyrins 58. 30 More interesting results were obtained when PdCl 2 was reacted with 47 in acetonitrile (Scheme 24).…”

“…39 p-Benziporphyrins have been shown to form complexes with Cd(II), Ni(II) and Zn(II), and evidence for weak η 2 -interactions has been noted. 40 The reaction appears to involve the initial formation of the hydroxy derivative 59 (Scheme 24). 40 Initially, a palladium(II) complex 57 was generated but upon treatment with potassium carbonate a ring contraction reaction took place affording palladium(II) carbaporphyrins 58.…”

“…30 More interesting results were obtained when PdCl 2 was reacted with 47 in acetonitrile (Scheme 24). 40 Aromatic palladium complexes related to 58 have also been prepared from benzocarbaporphyrins 41 and a carbachlorin. 40 The reaction appears to involve the initial formation of the hydroxy derivative 59 (Scheme 24).…”

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.…”

Phenanthriporphyrin: An Antiaromatic Aceneporphyrinoid as a Ligand for a Hypervalent Organophosphorus(V) Moiety

“…[1][2][3][4][5][6][7][8][9][10] Such compounds can demonstrate peculiar electronic and molecular structures and create au nique macrocyclic environment for coordination forcing atypical intermolecular reactivity.F or instance,acontraction of p-phenylene to cyclopentadiene is triggered by insertion of palladium(II) or gold(III) into p-benziporphyrin. [6,11,12] Herein, we report the synthesis and properties of an ew member of the aceneporphyrinoid class,n amely phenanthriporphyrin 4-H 3 (Scheme 1). Formally, 4-H 3 can be classified as adicarbaporphyrinoid, [13,14] that is,asaporphyrinoid with two carbon atoms in the core {CCNN}, but also as ap rototypical system containing the rigid phenathrenylene unit.…”