The Conformational Free Energy (ΔG) of the Nitro Group¹

Abstract

mations corroborated the structure of 3. Haller-Bauer cleavage with sodium amide led to an amide whose melting point (136.5-138.5°) corresponded to that reported (m.p. 135-136°) for 10.16 Conversion of 3 to its p-toluenesulfonylhydrazone (Ci6H2oN202S, and treatment with sodium methoxide in bis(2-ethoxyethyl) ether17 gave the tetracyclic hydrocarbon 11, prepared earlier.5The rearrangement of 1 -3 under alkaline conditions most reasonably proceeds through the homoenolate ion 2, formed by abstraction of a hydrogen from C-4 (or from its equivalent position C-9). The driving force in the isomerization may lie in a greater thermodynamic stability of 3, a factor that could also be of relevance in the solvolysis behavior of compounds with these skeletons.18

The Synthesis of gem-Halonitro Sugars and Their Conversion into Epoxynitro Sugars

“…The Br, method gave a crude product afforded methyl 4,6-0-benzylidene-3-chloro-3-(yield, 91%) which exhibited two spots on t.1.c. deoxy-3-nitro-a-D-gulopyranoside (13) 55:45. Upon chromatographic separation the pure crystalline epimers were isolated in yields of 49 and 33%.…”

Fast and efficient microwave synthetic methods for some new 2(1H)-pyridone arabinosides

“…The data obtained from 1 H NMR spectroscopy support this structure elucidation. Coupling constants were used to establish conformations in solution by the method of averaging of spin-spin coupling (Booth, 1964;Feltkamp and Franklin, 1965;Bozo and Kuszmann, 2000;Andrew and Walter, 2001). The spin-spin coupling J H1 ′ -H2′ < 4 Hz clearly shows that compound 5g is a β -isomer.…”

On the Thermodynamically Controlled Epimerization of Deoxynitroinositol Monomethyl Ethers

“…A rough estimate then leads readily t o the conclusion that these conforn~ers are highly disfavored so that one need consider only the alternate, equatorial nitro conformations. In the muco-3 isomer 4. the same problem does not arise since, in t h e axial nitro conformer, the nitro group does not interact with hydroxyls but with two hydrogen atoms instead, and for the latter interaction a value of 1.05 kcal/mol may be used (8). Another unknown parameter is the gauche interaction between an equatorial nitro group and a vicinal hydroxyl.…”