Tandem Insertion/[3,3]-Sigmatropic Rearrangement Involving the Formation of Silyl Ketene Acetals by Insertion of Rhodium Carbenes into S-Si Bonds

Allyl 2-diazo-2-phenylacetates are shown to react with trimethylsilyl thioethers in the presence of rhodium(II) catalysts to generate alpha-allyl-a-thio silyl esters. The transformation involves a tandem process involving formal rhodium-catalyzed insertion of the carbene group into the S-Si bond to generate a silyl ketene acetal, followed by a spontaneous Ireland-Claisen rearrangement. The silyl ester products were isolated as the corresponding carboxylic acids after aqueous workup. Intramolecular cyclopropanation of the allyl fragment generally competes with addition of the heteroatom to the carbene center. The reaction occurs under mild conditions and in high yield, allowing for rapid entry into rearrangement tetrasubstituted products. Propargyl esters were shown to generate the corresponding alpha-allenyl products.y

Automated summary

Allyl 2-diazo-2-phenylacetates react with trimethylsilyl thioethers in the presence of rhodium(II) catalysts to generate alpha-allyl-a-thio silyl esters. The reaction involves a tandem process of carbene group insertion into the S-Si bond and Ireland-Claisen rearrangement. The products are isolated as carboxylic acids after aqueous workup, with intramolecular cyclopropanation and heteroatom addition competing during the reaction.