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First, deprotonation of the heteroaryl sulfone (here, the benzothiazolyl sulfone) by a strong base (typically, lithium diisopropylamide) gives the α-sulfonyl carbanion. Then, the carbanion adds to the aldehyde carbonyl, forming a β-alkoxide intermediate. The β-alkoxide subsequently undergoes an intramolecular Smiles rearrangement: the alkoxide oxygen attacks the heteroaryl ring, displacing the sulfonyl group and forming a cyclic sulfonate intermediate. Finally, the cyclic sulfonate undergoes spontaneous β-elimination with loss of SO₂ and the heteroaryl anion, yielding the alkene. The E/Z-selectivity can be controlled by varying the sulfonyl group, solvent and base.