The tautomerism and stereochemistry of β‐sulphinyl enamines

The tautomeric equilibrium of β‐sulphinyl enamines in solution and the stereochemistry of its components have been studied by 1 H and 13 C NMR. The parent aliphatic β‐sulphinyl enamines bearing secondary alkylamino residues exist in two tautomeric forms in chloroform solution; the Z ‐enamine form always predominates over the E ‐imine form. α‐Alkyl‐substituted tertiary compounds exist in solution as a 4:1 mixture of E and Z isomers. NOE enhancements were measured in the two groups of compounds to confirm the stereochemical conclusions derived from the chemical shift interpretation.