Stereochemistry in substituted cyclopentanes: An approach to the analysis by proton NMR

Long‐range JCH heteronuclear coupling constants in cyclopentane derivatives

“…Moreover, we found that there is a relation between these 4 J HH values and the calculated dihedral angle between the corresponding hydrogens. 7,8 More recently, we have reported the detailed assignment of 1 H and 13 C NMR spectral data for various cyclopentanes. 9 In continuation of these studies, we began an investigation of the heteronuclear 2,3 J CH spin-spin couplings in some cyclopentane derivatives to verify their potential utility as a tool for determining the stereochemistry of substituents in these rings.…”

Synthesis of Enantiopure 1‐Azaspiro[4.5]decanes by Iodoaminocyclization of Allylaminocyclohexanes

“…The formation of 10 probably involved an initial cyclization to afford azaspiranic ring 11 (or a mixture of diastereomers) followed by a neighboring hydroxy group oxidation of the amine to give an iminium intermediate, [17] which was trapped by the hydroxy group to form the oxazolidine ring. [18] On the basis of the small coupling constant (J = 2.8 Hz) observed in the 1 H NMR spectrum for the methine protons, [19] we have assigned the stereochemistry of 10 to that shown in Figure 1 with a trans relationship between the linked heteroatoms at the pyrrolidine ring. Oxazolidine 10 was reduced (NaBH 4 ) [20] to azaspirane 11 in good yield and then, for analytical purposes, to 12 (Bu 3 SnH, AIBN).…”

Stereochemistry of cyclopentane derivatives from 2, 3JCH dependence on dihedral angle (θ HCCX)

“…Moreover, we found that there is a relation between these 4 J HH values and the calculated dihedral angle between the corresponding hydrogens. [8,9] In this field, we also reported the detailed assignment of 1 H and 13 C NMR spectral data for cyclopentanes 1-7b (Fig. 2).…”