Cyclohexane Compounds: Vi. Nuclear Magnetic Resonance Spectra of Some Derivatives of the Stereoisomeric 3-Bromo-1,2-Cyclohexanediols and the 2-Bromo-1,3-Cyclohexanediols

Abstract

First-order analysis of the 60 Mc.p.s. proton magnetic resonance spectra of la-inethoxy-28-acetoxy-3m-bromocyclohexane, lor-methoxy-2m-acetoxy-3p-bromocyclohexane, la-inethoxy-2p-bromo-3m-acetoxycyclohexane, lm-methoxy-2m-bromo-3p-acetoxycyclohexa1~e, and the corresponding diol diacetates confirmed the stereochemical interrelationships of substituents which were assigned previously on chemical grounds, and demo~istrated that the compounds exist in chair conformations. The chemical shifts of the ~ilethoxy methyl and acetoxy methyl protons did not provide reliable criteria for the assignment of conformations to these substituents in this series. The coupling constants of the methine protons followed, in general, the pattern predicted by the ICarplus equation, and the smaller J 2 , 3 values observed in the cis,trans compou~lds relative to those in the trans,trans compoundsare interpreted mainly on the basis of conformational equilibration, upon which is superimposed a small dihedral angular distortion or a remote substituent orientatio~ial effect.Analysis of the multiplet patterns and chemical shifts of the methine protons in the nuclear magnetic resonance spectra of the stereoisomeric 1-methoxy-2-acetoxy-3-acetylaminocyclohexanes Ia and IIa, their ethoxy analogues (Ic and IIc), and certain of their derivatives (Ib-Ie and IIb-IIe) (1) permitted unambiguous assignment of both gross structure and conformation to these compounds. This work also indicated that the chemical --.