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Polyphosphate ester (PPE, or ethyl metaphosphate) was proposed as a synthetic reagent in Phillips' benzimidazole synthesis. By the use of PPE, 2-substituted benzimidazoles were prepared in very mild conditions. Literatures on the polyphosphate ester were briefly reviewed and its constitution was discussed.
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Kanaoka et al. (1964) studied this question.
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