Carbon-13 NMR chemical shifts. A single rule to determine the conformation of calix [4] arenes

C Jaime, J De Mendoza, P Prados…

Index: Jaime, Carlos; Mendoza, Javier de; Prados, Pilar; Nieto, Pedro M.; Sanchez, Concha Journal of Organic Chemistry, 1991 , vol. 56, # 10 p. 3372 - 3376

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Citation Number: 541

Abstract

The conformations of calix [4] arenes can be deduced from the'9c NMR chemical shift of the methylene groups connecting each pair of aromatic rings. Inspection of 24 cases revealed that when the phenol rings beside each methylene are in a syn orientation (ie, in cone conformations), the methylene signals appear around S 31, whereas they appear around S 37 when both phenol rings are anti oriented (Le., in 1, 3-alternate conformations). Steric ...