β,β‐Diborylated Subporphyrinato Boron(III) Complexes as Useful Synthetic Precursors

Abstract

Iridium-catalyzed borylation of B-aryl meso-free subporphyrinato boron(III) complexes (hereinafter referred to simply as subporphyrins) with bis(pinacolato)diboron gave 2,13-diborylated subporphyrins regioselectively,w hich served as promising synthetic precursors for 2,13-diarylated subporphyrins and doubly b-to-b 1,3-butadiyne-bridged subporphyrin dimers.2 ,13-Diarylated subporphyrins display perturbed absorption spectra, depending upon the b-aryl substituents.D oubly 1,3-butadiyne-bridged syn and anti subporphyrin dimers thus prepared exhibit differently altered absorption spectra with split Soret-like bands,w hich have been accounted for in terms of exciton coupling.Subporphyrins are ring-contracted porphyrins possessing such intriguing characteristics as a1 4 p-aromatic system, bowl-shaped structures,and tunable absorption and emission properties.[1] Since the first synthesis of tribenzosubporphines in 2006, [2] various subporphyrins have been synthesized to explore their interesting optical, electronic,a nd structural attributes. [3,4] Despite these efforts,the development of novel synthetic methods that allow constructions of more elaborate subporphyrins still remains highly desired. In 2005, we reported iridium-catalyzed regioselective borylation of meso-free porphyrins at the b-positions adjacent to the free meso-position.[5a] This borylation has been demonstrated to be very effective,a llowing the synthesis of aw ide range of functional porphyrins including doubly butadiyne-bridged porphyrin dimers,s inglet biradicaloid doubly linked corrole dimer,a nd porphyrin belts.[5] Inspired by these rich progresses,w eplanned to develop b,b'-diborylated subporphyrins as precursors for further fabricated subporphyrins.Herein, we report borylation reactions of meso-free subporphyrins. [6] Initially,byfollowing the synthesis used for the porphyrin borylation, as olution of meso-free subporphyrin 1 (Scheme 1) and bis(pinacolato)diboron ((Bpin) 2 )i nT HF was refluxed for 9.5 hinthe presence of acatalytic amount of [{Ir(cod)OMe} 2 ]a nd 4,4'-di-tert-butyl-2,2'-bipyridyl (dtbpy). After the usual workup,however,weobtained an intractable mixture that contained b,b'-diborylated subporphyrins bearing aO -Bpin group at the axial position as am ajor product (55 %, 1 HNMR yield). [7] Since this product quickly decomposed on asilica gel column, the reaction mixture was directly subjected to reaction conditions (CuI and N-iodosuccinimide) that allowed the clean conversion of boronates to iodides. [8] This procedure yielded 2,13-diiodosubporphyrin 2 in 54 % yield after conversion of the axial group to am ethoxy group by heating in methanol. Thes tructure of 2 has been fully characterized including its X-ray crystal analysis (Figure 1a).These results indicated that the borylation took place with strict regioselectivity at the 2,13-positions,s imilarly to the borylation of meso-free porphyrins.To circumvent undesired borylation at the axial position, we employed B-aryl meso-free subporphyrins 3a and 3b as substrat...

Inhibition of the JAK2/STAT3/SOSC1 Signaling Pathway Improves Secretion Function of Vascular Endothelial Cells in a Rat Model of Pregnancy-Induced Hypertension

“…PIH causes the release of anti-angiogenic factors into the mother's circulation, resulting in endothelial injury [2,3]. Previous studies demonstrated that the combined treatment of anti-placental growth factor (PLGF) and vascular endothelial growth factor A (VEGF-A) could reduce ocular hemangiomas growth and choroidal neovascularization [28,29]. The activation of the SOCS/JAK/STAT signaling pathway is an essential pathogenic mechanism leading to endothelial cell dysfunction [30][31][32].…”

A meso–meso β‐β β‐β Triply Linked Subporphyrin Dimer

“…[19] Theabsorption spectrum of 15 was clearly different from that of doubly linked dimer 8 but rather similar to that of triply linked dimer 6,s uggesting substantial interaction through the Pt II -linkage. [15] Thee lectrochemical properties of 6, 9,a nd 15 were examined by cyclic voltammetry and differential pulse voltammetry ( Supporting Information, Figures S21-S23). Then arrow optical HOMO-LUMO gap clearly suggests the effective conjugation extending over the whole molecule.T he absorption bands at 315, 403, and 500 nm will be assigned as split Soret-like bands.T hese spectral features are different from those of triply linked porphyrin oligomers 5,w hich generally exhibit two split Soret-like bands.Asimilar trend was also observed in b-to-b doubly butadiyne bridged subporphyrin dimer,w hich has been attributed to the oblique arrangement of the two subporphyrin skeletons.…”

“…Thed oubly Pt II -bridged subporphyrin dimer 9 was synthesized by reacting b,b-diborylsubporphyrin 10 [15] with Pt(cod)Cl 2 in the presence of CsF and 1,5-cyclooctadiene (COD) in 64 %y ield (Scheme 2). It is worth noting that the syn isomer 9 was asole isolable product, and the corresponding anti isomer was not observed.…”

meso‐to‐meso Sulfide‐ and Disulf­ide‐Bridged Subporphyrin Dimers

“…[4][5][6][7][8][9][10][11] There are three positions available to functionalize subporphyrin, namely, the meso, , and axial positions. [4][5][6][7][8][9][10][11] There are three positions available to functionalize subporphyrin, namely, the meso, , and axial positions.…”

“…[7] It was, therefore, natural to expect even stronger electronic interactions to be observed in meso-to-meso butadiyne-bridged subporphyrin dimer 1 [8] and meso-to-meso directly linked subporphyrin dimer as indicated by femtosecond transient absorption anisotropy measurements and theoretical calculations. [10] We developed a method involving a nucleophilic aromatic substitution reaction (S N Ar) to introduce N-, O-, and S-based nucleophiles at the meso position of meso-halosubporphyrins. [9] both of which exhibited largely perturbed and broad Soretlike bands and redshifted Q-like bands.…”