Syntheses with Aliphatic Dialdehydes, XLV. – Substituted Glutaconaldehyde Derivatives by Vilsmeier Addition to 1‐Methoxy‐1‐buten‐3‐yne, 1‐Methoxy‐1‐penten‐3‐yne, and 1‐(Dimethylamino)‐1‐buten‐3‐yne and Their Reactions with Some Nucleophiles
3‐Halogeno‐substituted unsymmetrical pentamethinium salts 5, 7, 8, and 10 as well as 3‐halogeno‐substituted symmetrical vinamidinium salts 6, 9, and 11 are synthesized by addition of suitably substituted Vilsmeier reagents to 1‐methoxy‐1‐buten‐3‐yne (1). Analogous Vilsmeier additions to 1‐methoxy‐1‐penten‐3‐yne lead to 3‐halogen‐2‐methyl‐substituted unsymmetrical pentamethinium salts 13 and 14. Symmetrical 3‐methoxy‐and 3‐methylthio‐substituted vinamidinium salts 15 and 16 are observed by appropriate Vilsmeier additions to 1‐(dimethylamino)‐1‐buten‐3‐yne (4). Further 3‐substituted unsymmetrical and symmetrical pentamethinium salts are obtained by nucleophilic substitution at the C‐3 position of these salts, leading to 19–27. The [C4 + C1] pathway to 3‐substituted glutaconaldehyde derivatives represents a useful completion to their synthesis.