The anormeric effect in seven-membered rings: a comformational study of 1-oxa and 3-oxa derivatives of benzocycloheptene by nmr

S Désilets, M St-Jacques

Index: Desilets, S.; St-Jacques, M. Tetrahedron, 1988 , vol. 44, # 23 p. 7027 - 7036

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Citation Number: 7

Abstract

The 2-methoxy derivatives 5 and 7 of 3-and 1-benzoxepins (4 and 6 respectively) have been investigated by 13C and 1H dynamic NMR methods. The results reveal the presence of two conformer, Ca and Ce (94: 6), for 5 due to a strong endo-anomeric effect while for 7, the Ca: Ce population (5: 95) is opposite. Based on UV π→ π* spectral characteristics, it is deduced that delocalization of the n electrons of oxygen into the aromatic ring is not the major factor ...