✍ Scribed by Hartke, Klaus ;Bien, Notker ;Massa, Werner ;Wocadlo, Sigrid
No coin nor oath required. For personal study only.
o‐Alkyl substituted dithiobenzoates 3 are S‐methylated with trimethyloxonium tetrafluoroborate to form the stable bis(alkylthio)arylmethylium tetrafluoroborates 4. Their deprotonation with LiHMDS takes place either at the o‐alkyl groups to form the postulated o‐quinodimethanes 5 as intermediates or at the SMe groups to give the thiocarbonyl ylides 7. Both intermediates dimerize to furnish either the dibenzo[a,e]cyclooctenes 6 or the 1,4‐dithianes 8/9. Their trapping with N‐phenylmaleimide (10) leads to the formation of the cycloadducts 11 or 12. The structure of 8e was confirmed by X‐ray analysis. p‐Substituted dithiobenzoates 13 show a similar reaction sequence. Their bis(methylthio)arylmethylium salts, however, are only deprotonated at one of the SMe groups to give the 1,4‐dithianes 15/16. Sterically crowded 1,4‐dithianes (e.g. 8d,e/9d,e) rearrange with traces of acid to the ring opened stilbenes 18 and 19.
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