An
efficient and stereoselective method for the synthesis of (E)- and (Z)-α-silyl-α,β-unsaturated
amides and its synthetic applications are presented herein. The solvent-controlled
hydroaluminations of Si-substituted alkynes with DIBAL-H generate
diastereomerically enriched alkenylaluminum reagents that are directly
reacted with isocyanates at ambient temperature to afford α-silyl-α,β-unsaturated
amides in high yields with retained stereoselectivity. In particular,
this process enables the synthesis of a broad range of (E)-α-silyl-α,β-unsaturated amides, which are the
less studied isomers. The synthetic utility of this method is highlighted
by its short reaction time, ease of purification, easily accessible
substrates and reagents, gram-scale synthesis, and the further transformations
of C–Si bonds into C–H, C–X, and C–C bonds.
1,2-Diborons with one boron atom each in the allyl and homoallyl positions are of great utility, especially as doubleallylation reagents. However, only a few synthetic methods have been reported to date and have a limited substrate scope. Herein, we developed the Cu-catalyzed regio-and stereoselective synthesis of α-borylmethyl-(E)-allylborons from easily accessible 1-substituted allenols and bis(pinacolato)diboron. Importantly, this method allowed the highly efficient and regioselective formation of doubleallylating diborons with diverse substituents, which would be otherwise cumbersome to synthesize, and could be successfully performed on a gram scale. The synthetic application of α-borylmethyl-(E)-allylborons was demonstrated by the enantio-and (Z)selective allylation of aldehydes via Brønsted acid catalysis. Furthermore, (E)-allyl and (E)-homoallyl diols with excellent diastereoselectivity were generated by the Lewis acid catalyzed diastereo-and (E)-selective allyl transfer of (E)-allyldiborons to aldehydes. Using this strategy, the key intermediate in the construction of the C 7 −C 12 fragment of (−)-discodermolide was also synthesized.
A broad range of alkynamides were efficiently synthesized through Et3N-catalyzed alumination of terminal alkynes with AlMe3, followed by nucleophilic addition of alkynylaluminums to isocyanates.
The highly regioselective copper‐catalyzed hydroaminations of terminal or γ‐substituted allylic sulfones with aromatic amines is described. The combination of an N‐heterocyclic carbene‐copper complex and KOt‐Bu plays an important role in promoting selective amination under mild reaction conditions. This catalytic reaction tolerates a wide range of functional groups and enables the efficient syntheses of new and versatile functionalized β‐amino sulfones in high yields (up to 98%) with >98% regioselectivity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.