Stille coupling reactions, Shapiro reaction

Liebeskind and associates converted 3,4-diisopropyl squarate (97) to stannylcyclobutenedione 98 via a 1,4-addition-elimination sequence. 98 was then coupled with 2-iodothiophene to afford substituted cyclobutenedione 99 [85]. In another case, 3-lithioquinuclidin-2-ene, generated from the Shapiro reaction of 3-quinuclidinone (100), was quenched with Bu3SnCl to afford a unique enamine stannane 101. The Stille reaction of stannane 101 and 5-bromo-2-formyl-thiophene then furnished 3-thienylquinuclidine 102 [86]. 

The Shapiro reaction has also been used to convert sulfonylhydrazones into alkenylstannanes or alkenylboronic acids, which have been employed in Pd-catalyzed Stille or Suzuki coupling reactions.14,15 For example, Keay has described a one-pot... 

---