Synthesis of alkyl allenyl sulfoxides from thiosuccinimides via [2,3]-sigmatropic rearrangement

With the instability and alternative reactive modes of alkyl sulfenyl chlorides making the synthesis of a broad range of alkyl allenyl sulfoxides via the [2,3]-sigmatropic rearrangement difficult, alternative sources of electrophilic sulfur were explored. Examination of various N-sulfanylimides revealed that thiosuccinimides are a viable sulfur source for the synthesis of alkyl allenyl sulfoxides via the [2,3]-sigmatropic rearrangement. With the optimized conditions of excess propargyl alcohol and potassium carbonate in chloroform at 50 degrees C, a variety of alkyl allenyl sulfoxides were synthesized in fair to good yields (21-73%, 21 examples). Additionally, butyn-1,4-diols can be selectively monofunctionalized with a large excess of diol and stoichiometric triethylamine in THF at room temperature to form 1-hydroxyalkyl allenyl sulfoxides (26-71%). These diols can also be bis-functionalized to form 2,3-disubstitued dienes (53-66%) via two separate [2,3]-sigmatropic rearrangements. The formation of alkyl allenyl sulfoxides was also found to be selective for less substitution at the propargyl position (3:1-100:0 ratio) as shown in direct competition experiments. Trimethylsilylethyl thiosuccinimides were among the highest yielding of the thioimides. The sulfenate chemistry of select allenyl sulfoxides can be successfully performed.

Automated summary

By exploring alternative sources of electrophilic sulfur, thiosuccinimides were found to be a viable sulfur source for the synthesis of alkyl allenyl sulfoxides via the [2,3]-sigmatropic rearrangement. With optimized conditions, a variety of alkyl allenyl sulfoxides were synthesized in fair to good yields. Additionally, butyn-1,4-diols can be selectively monofunctionalized to form 1-hydroxyalkyl allenyl sulfoxides or bis-functionalized to form 2,3-disubstitued dienes.