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Rings of various shapes and sizes: Spirocyclic hydrocarbons 2 were obtained in good to excellent yield through the triflic acid (TfOH) catalyzed cyclization of alkynyl-substituted cyclic tertiary alcohols 1 under mild conditions with good control of ring size (see scheme). The method was extended to the synthesis of bridged bicyclic ketones with high stereoselectivity.
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Jin et al. (2009) studied this question.
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