RESEARCHES ON UNSATURATED KETONIC ACIDS. I. THE CONSTITUTION OF THE SO-CALLED “PECHMANN DYES” AND THE MECHANISM OF THEIR FORMATION FROM BETA-BENZOYLACRYLIC ACID^1,2

Abstract

CONSTITUTION OF THB PECHMANN DYES 2871 £-Sulfobenzene-azo-(4-phenyl-2-aminothiazole), from diazotized sulfanilic acid and the thiazole, was precipitated as the sodium salt by the usual salting-out process. Recrystallized from water and dried, it formed a dark red solid of bronze luster, which dissolved freely in water giving a crimson-red solution, that changed in color to pale yellow when acidified, and regained its original color when made alkaline again. Summary 1. 2-Aminothiazoles, prepared from -chloro derivatives of aldehydes or ketones and thio-urea, were condensed with aromatic aldehydes in the presence of hydrochloric acid, to di(aminothiazyl)phenylmethanes, which were then oxidized by lead dioxide in acid solution to the corresponding carbinols, whose mono-acid salts lost a molecule of water and formed di(aminothiazyl)phenylmethane dyes of Doebner Violet type, but which dyed silk, wool or mordanted (tannined) cotton, a dull bluegreen. As dyes, they were inferior to Malachite Green.2. The war "gases" used as initial materials were dichloro ether (for chloro-acetaldehyde), chloro-acetone and chloro-acetophenone; the thiazoles were the 4-methyl-, and 4-phenyl-2-aminothiazoles; and the aromatic aldehydes with which they were condensed were benzaldehyde, its pchloro-, o-, m-and p-nitro-, ^-dimethylamino-, o-and ^-hydroxy-derivatives and piperonal.3. The 2-aminothiazoles were used also as couplers for the production of new azo dyes. New York, N. Y.

π‐Extented Conjugated Polymers Entailing Pechmann Dye Moieties for Solution‐Processed Ambipolar Organic Semiconductors

“…[2,4,5,9] Recently, we have reported a new electron acceptor: bipyrrolylidene-2,2'(1H,1'H)-dione (BPD), which is derived from an old synthetic dye (Pechmann dye). [10] Similar to DPP and isoindigo, BPD owns planar and polar structure with bis-amide as electron withdrawing units. Alkyl chains can be introduced to amide groups to improve solubility (Scheme 1).…”

Time-dependent density functional theory (TDDFT) modelling of Pechmann dyes: from accurate absorption maximum prediction to virtual dye screening

“…1). 12 Pechmann dye (1) can be thermally rearranged in protic solvents, or under basic conditions 13 to an endo-fused 6-membered dilactone (2) with a concomitant hypsochromic shift of the absorption maximum resulting in a colour change from red to orangeyellow. Both lactones are fluorescent (in yellow and green, respectively) in nonpolar solvents.…”

Thiophene‐Containing Pechmann Dyes and Related Compounds: Synthesis, and Experimental and DFT Characterisation

“…[33] Similarly to Perkin, Hans von Pechmann attempted in 1882 to dehydrate b-benzoylacrylic acid to naphthoquinone based on their stoichiometric relationship only to obtain a new, bright red compound. [8] The structure of the "Pechmann dye" was conclusively determined in 1924 [9] to be a 4-phenyl-3-butenolide dimer ( Figure 1) with the two lactones joined by an exo double bond at the a-carbon atom in a trans fashion (Pechmann lactone, PLN, I). Stepwise, twofold amidation of I leads to a redshift in the corresponding mono-and dilactams (Pechmann lactam-lactone, PLMN, II and Pechmann lactam, PLM, III, respectively).…”