Synthesis and characterization of symmetric and non-symmetric bisspiropyranylethyne

Symmetric bis-spiropyrans have been synthesized by the reaction of 5-[2-(3-formyl-4hydroxyphenyl)ethynyl]-2-hydroxybenzaldehyde, which had previously been prepared by a palladium-catalyzed reaction of 2-hydroxy-5-iodo-benzaldehyde and 5-ethynyl-2hydroxybenzaldehyde, with 2 equiv. of Fischerʹs bases. Non-symmetric bis-spiropyrans were synthesized by palladium-catalyzed reaction of 6-iodospiropyrans with 6-ethynylspiropyrans, which had been prepared by reaction of 2-hydroxy-5-iodobenzaldehyde with 1 equiv. of Fischerʹs base, and the reaction of 5-ethynyl-2-hydroxybenzaldehyde with 1 equiv. of Fischerʹs base respectively. The bis-spiropyrans obtained were characterized by 1H NMR, IR spectroscopy, UV and GC-MS.