Do spiroarsoranes exhibit polytopal equilibrium in solution?
The spiroarsoranes 5-phenyl-1,6-dioxa-4,9-diaza-5lambda(5)-arsaspiro[4.4]nonane (6), (3R,8R)-3,8-dimethyl-5-phenyl-1,6-dioxa-4,9-diaza-5lambda(5)-arsaspiro[4.4]nonane (7), (2S,7S)-2,7-dimethyl-5-phenyl-1,6-dioxa-4,9-diaza-5lambda(5)-arsaspiro[4.4]nonane (8), and (3S,8S)-3,8-dimethyl-(2R,7R)-2,5,7-triphenyl-1,6-dioxa-4,9-diaza-5lambda(5)-arsaspiro[4.4]nonane (9) were prepared by reaction of phenylarsonic acid and the correspondig amino alcohol. The presence of polytopal Delta left arrow over right arrow Lambda equilibrium in 6-9 was demonstrated by HPLC and NMR studies. NBO computations at the MP2/6-31+G(2d,2p) level indicate that methyl substitution in C2 or C3 of the oxazarsolane ring determines the predominance of Delta or Lambda stereoisomers. GIAO B3LYP/6-311++G(2d,2p) computations were used to assign experimental (1)H and (13)C NMR spectra.
Tapia-Benavides
Antonio R
AR
Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Hidalgo, Carretera Pachuca-Tulancingo Km. 4.5, Mineral de la Reforma, 42184 Hidalgo, México.
Mendoza-Huizar
Luis H
LH
Pérez-García
Francisco
F
Tlahuext
Hugo
H
Alvarez
Alejandro
A
Tlahuextl
Margarita
M