Applications of Allenylsilanes in Organic Synthesis

All articles of this category Introduction Allenylsilanes 2 are versatile reagents widely used in organic synthesis.[ 1 ] Generally, allenylsilanes react as propargyl anion equivalents in Lewis acid mediated[ 2 ] or thermal[ 3 ] nucleophilic addition to electrophiles such as carbonyls, imines, Selectfluor, and N -bromosuccinimide, etc.[ 1 ] [ 4 ] [ 5 ] The regiospecific addition of allenylsilanes provides a β-vinyl cation, which is stabilized by a C–Si bond, which is called β effect. The C–Si bond in allenylsilanes is oriented cis-coplanar to the p-orbital of the carbocation and provides direct stabilization.[ 5 ] Allenylsilanes undergo [3+2] annulations with α,β-unsaturated carbonyls, carbonyl compounds, imines, and nitrosyl cations to form cyclo-pentenones, dihydrofurans, dihydropyrroles, and isoxazoles, respectively.[ 1 ] [ 4 ] [ 5 ] The efficient methods for the synthesis of allenylsilanes 2 are copper-mediated 1,3-substitution reactions of carbon nucleophiles to propargylic substrates 1 having a leaving group at the propargylic position.[ 6 ] [ 7 ] Scheme 1 Synthesis of allenylsilanes