Highly distorted and rigid cone conformers of calixarene have been synthesized by low-valent titanium promoted intra-molecular coupling of aldehydes 1a-d. The reaction outcome strongly depends on the substituents present at the upper rim and reaction time. In all cases examined infra-molecular coupled compounds, having a bridge only two atoms long, were obtained in about 30% yield. © 1995 Elsevier Science Ltd.
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