Synthesis of 1,1-Disubstituted Allenylic Silyl Ethers through Iron-Catalyzed Regioselective C(sp2)–H Functionalization of Allenes

Abstract

We report a synthesis of allenylic silyl ethers through iron-catalyzed functionalization of the C(sp2)−H bonds of monosubstituted alkylallenes. In the presence of a cyclopentadienyliron dicarbonyl based catalyst and triisopropylsilyl triflate as a silylation agent, a variety of aryl aldehydes were suitable coupling partners in this transformation, furnishing a collection of 1,1-disubstituted allenylic triisopropylsilyl ethers as products in moderate to excellent yields as a single regioisomer. Lithium bistriflimide was identified as a critical additive in this transformation. The optimized protocol was scalable, and the products were amenable to further transformation to give a number of unsaturated, polyfunctional derivatives.

Iron-Catalyzed Coupling of Alkenes and Enones: Sakurai–Michael-type Conjugate Addition of Catalytic Allyliron Nucleophiles

“…More hindered reagents gave significant improvements in the yield (entries 8–10). Finally, with TIPSOTf selected as the silylating reagent, the incorporation of substoichiometric LiNTf 2 as an additive was found to further improve the reactivity, delivering 3aa in 82% isolated yield (entry 11).…”