Intramolecular fixation of t-butyl groups in thiolactim ethers influencing molecular conformation and the packing behavior

• A new intramolecular hydrogen bonding motif is found and characterized.
• Results from X-ray crystallography are supported by DFT calculations.
• Conformation of t-butyl thiolactimethers predictably influences the packing behavior.
• Selective cleavage of a t-butyl blocking group.

Derived from the result of a previous crystallographic study regarding an ethynylene bridged bispyrimidine, the presence of two intramolecular C–H⋯N hydrogen bonding contacts being responsible for a fixation of the terminal t-butylthio units to the azine nitrogens was noticed. Acting as stimulus, a series of different pyridine and pyridazine derivatives also featuring this unusual functionality has been synthesized and structurally studied. In order to support the investigations concerning this particular bonding pattern performed via X-ray structure analysis, calculations based on the density functional theory were carried out. It was found that the formation of the intramolecular hydrogen bonding motif has not only impact on the molecular stability but in some cases also predictably influences the reactivity and the packing behavior of the different heterocycles.

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