Boryl-group-assisted reductive C−C bond cleavage of 1,2-diaryl-1,2-diborylethanes is described. The substrates, 1,2-diaryl-1,2-diborylethanes, are synthesized by reductive diboration of stilbenes. The combination of these reactions, reductive diboration and reductive cleavage provides a new strategy for reductive C=C double bond cleavage.

Abstract

In contrast to the well-established oxidative C=C double bond cleavage to give the corresponding carbonyl compounds, little is known about reductive C=C double bond cleavage. Here we report that C−C single bond cleavage in 1,2-diaryl-1,2-diborylethanes proceeds by reduction with sodium metal to yield α-boryl benzylsodium species. In combination with our previous reductive diboration of stilbenes, the overall transformation represents reductive cleavage of the C=C double bonds of stilbene to yield α-boryl-α-sodiated toluenes. This reductive two-step C=C double bond cleavage is applicable to ring-opening or ring-expansion reactions of polycyclic aromatic hydrocarbons.