| Abstract: | Surprising Reaction of 5‐(Phenylthio)‐ and 5‐(Methylthio)pent‐2‐en‐4‐inal with HCl Contrary to expectations (Scheme 1), 5‐(phenylthio)‐( 1a ) as well as 5‐(methylthio)pent‐2‐en‐4‐inal ( 1b ) react with a slight excess of HCl to give 2‐bis(phenylthio)methyl]furan ( 17a , 77% yield) and 2‐bis(methylthio)methyl]furan ( 17b , 61% yield), respectively. Structures 17a and 17b are supported by the results of an X‐ray crystal‐structure analysis, by spectroscopic data in comparison to those of model compounds, and by synthesis of 17a . This surprising reaction is tentatively explained by a mechanism (Scheme 4), including a special pyran→furan ring‐contraction sequence, which is in agreement with a labelling experiment. |
