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The Ugi four‐component condensation between 1,1‐diethoxy‐2‐isocyanoethane (2), cycloketones 1, amine hydrochlorides 4, and potassium thiocyanate (3a) or selenocyanate (3b) affords spiroimidazoles 5, which are cyclized to spiroimidazo[1,5‐a]imidazole‐5‐thiones (or selenones) 6.
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BOSSIO et al. (1993) studied this question.
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