Silicon-Controlled Intramolecular Thermal H-Ene Reaction – A New Access to a Key Intermediate of (±)-cis-γ-Irone

Abstract

The primordial influence of the silyl group in an intramolecular thermal H‐ene reaction is reported. The silyl group lowered the energy of the transition state and allowed the reaction to proceed at a lower temperature than that of the simple all‐carbon analog, thereby excluding the formation of undesirable by‐products. This sequence has been applied for new access to a key intermediate in the diastereoselective synthesis of (±)‐cis‐γ‐irone with high chemocontrol and significantly improved overall yield.

Intramolecular Ene Reaction of Epoxyallylsilanes: Synthesis of Allyl- and Vinylsilane-Functionalized Cyclohexanols

“…From the classical mechanistic standpoint, it is generally agreed that the concerted ene reaction of allylsilanes involves a highly asynchronous transition state featuring a well-developed C−C bond prior to a relatively late proton transfer toward the oxygen . Consequently, the ene transition state has dipolar character, and the silyl group, which enhances the nucleophilicity of the double bond, is also a powerful force for the stabilization of the partial positive charge at the β-carbon atom.…”

Allylsilanes in the synthesis of three to seven membered rings: the silylcuprate strategy

“…This is the case of analogous allylsilanes bearing the bulky t-butyldiphenylsilyl group, which give 3-cyclopenten-1-ols maintaining the hindered silyl group. [11,12]…”

Intramolecular Cyclization of tert-Butyldiphenylallylsilane Units and Carbonyl Groups: Allylsilane Terminated Cyclization versus the Ene Reaction

“…Allylsilanes are known to give ene reactions, either under thermal or acid-catalyzed conditions. From the classical mechanism standpoint, it is generally agreed upon that the concerted ene reaction involves a highly asynchronous transition state featuring a well-developed C−C bond prior to a relatively late proton transfer toward the oxygen .…”