TY - JOUR
T1 - Lack of manifestation of an anomeric effect in 2‐diphenylphosphinoyl‐1, 3‐dioxane and 2‐diphenylphosphinoyl‐1, 3‐oxathiane1
AU - Juaristi, E.
AU - Flores‐Vela, A.
AU - Labastida, V.
AU - Ordoñez, M.
PY - 1989/6
Y1 - 1989/6
N2 - The spectroscopic evidence for the predominance of the equatorial conformers in the title compounds was confirmed by the study of derivatives containing counterpoise substituents, and by chemical equilibration of anancomeric models. ΔG 27o°C [P(O)Ph2] ≳ 3·2 kcal/mol was determined in the dioxane, and ΔG 55o°C [P(O)Ph2] = 1·42 ± 0·12 kcal/mol in the oxathiane. It follows then that the strong anomeric interaction observed previously in SCP segments does not show up in the six‐membered heterocycles 2 and 7, which contain OCP moieties. This may be due to an inherent inability of oxygen to act as an electron donor to the axial P(O)Ph2 substituent, or to a dominant repulsive steric interaction in the axial conformers.
AB - The spectroscopic evidence for the predominance of the equatorial conformers in the title compounds was confirmed by the study of derivatives containing counterpoise substituents, and by chemical equilibration of anancomeric models. ΔG 27o°C [P(O)Ph2] ≳ 3·2 kcal/mol was determined in the dioxane, and ΔG 55o°C [P(O)Ph2] = 1·42 ± 0·12 kcal/mol in the oxathiane. It follows then that the strong anomeric interaction observed previously in SCP segments does not show up in the six‐membered heterocycles 2 and 7, which contain OCP moieties. This may be due to an inherent inability of oxygen to act as an electron donor to the axial P(O)Ph2 substituent, or to a dominant repulsive steric interaction in the axial conformers.
UR - http://www.scopus.com/inward/record.url?scp=84987014212&partnerID=8YFLogxK
U2 - 10.1002/poc.610020406
DO - 10.1002/poc.610020406
M3 - Artículo
AN - SCOPUS:84987014212
SN - 0894-3230
VL - 2
SP - 349
EP - 358
JO - Journal of Physical Organic Chemistry
JF - Journal of Physical Organic Chemistry
IS - 4
ER -