Conformational Analysis in Heterocyclic Systems: Recent Results and Applications

Abstract

Abstract This review deals with the following aspects of conformational analysis in saturated heterocyclic systems: 1. Conformational equilibria in 2‐aryl and 2‐ethynyl‐1,3‐dioxanes in various solvents. 2. The generalized anomeric effect in perhydro‐1,3‐diazines and its origin. 3. Unexpected conformational equilibria in 5‐heterosubstituted 1,3‐dioxanes. 4. Normal and anomalous solvent effects in conformational equilibria of 1,3‐dioxanes with heteroatoms at C‐5. Calculation of solvent effects. Correlation of Δ G 0 as a function of solvent with solvatochromic transition energy E T (30); a new scale of “solvent polarity”. 5. Interplay of hydrogen bonding with dipolar, non‐bonded and eclipsing interactions in 5‐hydroxymethyl‐ 1,3‐dioxanes. 6. Highly stereoselective H‐D exchanges in anancomeric 1,3‐dithianes. 7. Potential distortion of a cyclohexane or 1,3‐dioxane ring by a tert ‐butyl substituent. Evidence from 1 H‐NMR and 13 C‐NMR investigations and from X‐ray structure analysis.