TY - JOUR
T1 - Conformational studies on 1,3-dioxepans. Part I. 1,3:2,5:4,6-tri-O- methylene-D-mannitol and some related compounds
AU - Grindley, T. B.
AU - Stoddart, J. F.
AU - Szarek, W. A.
PY - 1969/1/1
Y1 - 1969/1/1
N2 - N.m.r. studies on 1,3:2,5:4.6-tri-O-methylene-D-mannitol (in thionyl chloride from ambient temperature down to -82°) and on 1,3:4,6-di-O- benzylidene-2,5-O-methylene-D-mannitol indicate that the 2,5-O-methylene protons are magnetically equivalent. This may be interpreted in two ways. Either the 1,3-dioxepan ring is undergoing a fast ring-inversion process or it exists predominantly in the conformationally stable twist-chair (TC) or twist-boat (TB) forms, in which the 2,5-O-methylene protons are magnetically equivalent on account of C2 symmetry. Conformational analysis predicts that the conformation containing the TC form is more stable than those containing the TB or chair (C) forms. It is also proposed that the TC form is the most stable for the 1,3-dioxepan ring of 1,3:4,6-di-O-methylene-2,5-O-isopropylidene-D-mannitol.
AB - N.m.r. studies on 1,3:2,5:4.6-tri-O-methylene-D-mannitol (in thionyl chloride from ambient temperature down to -82°) and on 1,3:4,6-di-O- benzylidene-2,5-O-methylene-D-mannitol indicate that the 2,5-O-methylene protons are magnetically equivalent. This may be interpreted in two ways. Either the 1,3-dioxepan ring is undergoing a fast ring-inversion process or it exists predominantly in the conformationally stable twist-chair (TC) or twist-boat (TB) forms, in which the 2,5-O-methylene protons are magnetically equivalent on account of C2 symmetry. Conformational analysis predicts that the conformation containing the TC form is more stable than those containing the TB or chair (C) forms. It is also proposed that the TC form is the most stable for the 1,3-dioxepan ring of 1,3:4,6-di-O-methylene-2,5-O-isopropylidene-D-mannitol.
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U2 - 10.1039/j29690000172
DO - 10.1039/j29690000172
M3 - Article
AN - SCOPUS:0003531655
SN - 0045-6470
SP - 172
EP - 175
JO - Journal of the Chemical Society B: Physical Organic
JF - Journal of the Chemical Society B: Physical Organic
ER -