Synthesis of isomeric benzodipyrrolenines and their derivatives

Synthesis, Photophysical and Electrochemical Properties of Bis‐Squaraine Dyes Fused on Isomeric Benzodipyrrole Central Units

“…Silica gel (SiO 2 , spherically shaped, neutral) for the column chromatography was purchased from Kanto Chemical (Tokyo). 3-[4-(Dibutylamino)phenyl]-4hydroxy-3-cyclobutene-1,2-dione 2 [CAS 155172-87-5], [40] 2,3,3,5,5,6hexamethyl-3H,5H-benzo[1,2-b:5,4-b']dipyrrole 4 [CAS 35093-62-0], [34,35] 2,3,3,6,7,7-hexamethyl-3H,7H-benzo[1,2-b:4,5-b']dipyrrole 5 [CAS 35085-89-3] [38] were prepared according to the literature procedure.…”

“…Two benzodipyrrole isomers, benzo[1,2-b:3,4-b']dipyrrole 3 and benzo[1,2-b:5,4b']dipyrrole 4, were used for the central components and prepared by the Fischer indole synthesis according to a previous report. [34,35] Since 3 and 4 bearing activated methyl group can act as nucleophile and be used for the syntheses of bis-styryle dyes and bis-cyanine dyes, they can react with squaric acid and its derivative. [36][37][38] The condensation of N,Ndibutylaniline and 1,2-dichlorocyclobuten-3,4-dion, obtained by the reaction of squaric acid with oxalyl chloride and subsequent hydrolysis reaction, yielded monosubstituted squaric acid (2).…”

“…The dye was obtained in 75% yield by condensation of 5 synthesized from p-phenylenediamine with compound 2. [34,38] For the comparative examination, squaraine dye 1 of the monomeric chromophore was also synthesized according to a previous report. [41] Squaraine dyes consisting of N-alkylated indolenine moieties adopt sterically distorted s-trans conformations in which dimethyl groups of indolenine are oriented towards cyclobutenediones.…”

The synthesis, structure and spectral properties of new long-wavelength benzodipyrroleninium-based bis-styryl dyes

“…Bis-styryl dyes 3ae3c were synthesized in good yields (45e60%) via condensation of benzodipyrrolenine di-quaternary salt 5 [38] with two equivalents of 4-dimethylaminobenzaldehyde, 4-(3,5-diphenyl-4,5-dihydro-1H-1-pyrazolyl)benzaldehyde [37] and 4-dimethylaminocinnamoic aldehyde, respectively, in acetic anhydride under reflux (Scheme 4). The formation of undesirable monocondensation product was avoided by addition of an excess of aldehyde.…”

“…f] indolediium diiodide (5) [38] 0.45 g of benzodipyrrolenine [38] was refluxed in large excess of methyl iodide for 7 h. The reaction mixture was diluted with ether; the obtained precipitate was filtered off, washed with ether and dissolved in chloroform. The salt 5 was filtered off and washed with chloroform.…”