- Bis-indolyl phthalides and naphthalides
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This invention relates to indole phthalein indicator dyes including phthalides and naphthalides wherein one of the indol-3-yl radicals is substituted with a hydrogen-bonding group on a carbon atom adjacent to the nitrogen atom of the indole ring. In a preferred embodiment, one of the indol-3-yl radicals is substituted with a hydrogen-bonding group and the other indol-3-yl radical is substituted with a hydrogen-bonding group or with an electron-withdrawing group. These indicator dyes, especially those of the preferred embodiment, possess a relatively high pKa and a relatively broad absorption spectrum in the visible range.
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- Phthalide and naphthalide derivatives
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This invention relates to a process of preparing phthalein indicator dyes including phthalides and naphthalides derived from certain hydroxy-substituted carbocyclic aryl compounds, such as phenols, and from certain N-heterocyclic aryl compounds, such as indoles, and to a process of preparing novel intermediates useful therein. According to the present invention, the selected carbocyclic compound or the selected N-heterocyclic compound is reacted with phthalaldehydic or naphthalaldehydic acid to form the corresponding (na)phthalidyl adduct which is treated with an oxidizing agent to yield the subject intermediates. To prepare the indicator dye, the intermediate, i.e., the oxidation product thus obtained is then reacted with a carbocyclic or heterocyclic aryl compound to yield the corresponding indicator dye. The oxidation products comprising the novel intermediates of the present invention may be dehydro or hydrated (na)phthalidyl adducts.
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- 3-(Indol-3-yl)dehydronaphthalide hydrochlorides
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This invention is concerned with a novel class of protonated compounds, namely, 3-(indol-3-yl)dehydronaphthalide hydrochlorides, with their synthesis by the reaction of a 3-(indol-3-yl)naphthalide and a high-potential quinone in an inert anhydrous aprotic solvent in the presence of a carboxylic acid catalyst, and with the synthesis of indole naphthalide indicator dyes by reacting the said dehydronaphthalide hydrochlorides and an indole in an aromatic hydrocarbon solvent in the presence of a carboxylic acid catalyst.
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