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A general, chemoselective approach to 3-substituted coumarins via Baylis–Hillman reactions of O-benzylated salicylaldehyde precursors has been demonstrated. Competitive cyclization to chromene derivatives is inhibited by conjugate addition of benzylamine or piperidine to the α,β-unsaturated ester intermediates.
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Kaye et al. (2003) studied this question.
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