Sulfonylhydrazones, Shapiro reaction

Most Shapiro reactions of acyclic sulfonylhydrazones or cyclic sulfonylhydra-zones derived from larger rings proceed with selectivity for the formation of the E-vinyllithium reagent. For example, the trisylhydrazone generated from 4-heptanone (12)... 

The conditions originally employed for the Shapiro reaction involved treatment of the sulfonylhydrazone derivative with an alkyllithium reagent in hexane or ether solvent. Although these conditions are quite effective for the conversion of sulfonylhydrazones to alkenes (e.g., 1—>2), efforts to capture the intermediate vinyllithium reagent with electrophiles other than H+ are often met with limited success due to competing deprotonation of the solvent or the sulfonyl aryl group by the basic vinyllithium species. For example, treatment of 15a with >2 equiv of n-BuLi in hexane followed by quenching with D2O provided 16 in quantitative yield but with only -10% deuterium incorporation. A solution to this problem was developed independently by Shapiro and Bond that employs TMEDA (tetramethylethylenediamine) as an additive for Shapiro reactions.7,10 As shown below, use of TMEDA (4.0 equiv) as a cosolvent led to the conversion of 15b to 16 in quantitative yield with 95% deuterium incorporation. 

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... 

The a-alkylation of sulfonylhydrazone dianions with disulfides followed by Shapiro reaction has been used to effect the 1,2-transposition of carbonyl groups.19,20 As shown below, treatment of tosylhydrazone 31 with n-BuLi/TMEDA followed by addition of dimethyl disulfide and deprotonation with an additional equivalent of w-BuLi provided vinylsulfide 32.19 Exposure of this compound to mercuric chloride in hot aqueous acetonitrile provided ketone 33 in 75% overall yield. 

---