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NMR study of 2‐alkoxy‐1,3,2‐dioxaphospholanes. II—molecular conformation of alkoxy substituents
Author(s) -
Besserre D.,
CoffiNketsia S.
Publication year - 1980
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270130502
Subject(s) - alkoxy group , lone pair , chemistry , substituent , steric effects , ring (chemistry) , chemical shift , stereochemistry , crystallography , group (periodic table) , medicinal chemistry , molecule , alkyl , organic chemistry
The conformation of some 2‐σ‐1,3,2‐dioxaphospholanes (σ=OAlkyl, CI) is studied. The determination of the 2 J (POC) and 3 J (POCC) coupling constants, which are influenced by the bulk of the alkoxy group, is a means of obtaining information about the rotation around the POR bond, which is dependent on steric interactions between the phosphorus lone pair, the alkoxy group and the substituents on the ring. When σ is a tert ‐butoxy group, a direct ‘through‐space’ interaction is found between the phosphorus atom and one of the primary carbons of the OR group. If there is no substituent on the ring, the 31 P chemical shifts are little affected by changes in OR; a diamagnetic effect is observed, however, in the case of the tert ‐butoxy group which is enhanced for the 4,4,5,5‐tetramethyl derivatives.