Vinyl silanes offer a regio- and stereoselective route to alkenes – E vinyl silane

Jmol.jmolButton(jmolApplet0, 'load ../model/organo_main_group/silicon/vinyl_silanes/e/1.xyz;hide atomno=1 or atomno=13 or atomno=14 or atomno=15 or atomno=16 or atomno=17 or atomno=18 or atomno=19 or atomno=20 or atomno=21 or atomno=22 or atomno=23 or atomno=24 or atomno=25 or atomno=26 or atomno=27 or atomno=28 or atomno=29 or atomno=30;wireframe 0.1;spacefill 20%;moveto 0.0 -792 490 -363 144.25;select all;set labelOffset 0 0;font label 18 ariel bold;color label black;connect (atomno=10) (atomno=11) DOUBLE;connect 1.335 1.36 (atomno=2) (atomno=3) AROMATIC;connect 0.5 1.335 (atomno=2) (atomno=3) DOUBLE;connect 2 2.45 (atomno=3) (atomno=10) PARTIAL;connect 0.5 2 (atomno=3) (atomno=10) SINGLE;wireframe 0.1;select atomno=4;label R1;select atomno=6;label R2;select atomno=10 and model=1.1;label +;select atomno=10 and model=1.2;label +;select atomno=10 and model=1.3;label +;select atomno=10 and model=1.4;label +;select atomno=10 and model=1.5;label +;select atomno=10 and model=1.6;label +;select atomno=10 and model=1.7;label +;select atomno=10 and model=1.8;label +;select atomno=10 and model=1.9;label +;select atomno=10 and model=1.10;label +;select atomno=10 and model=1.11;label +;select atomno=10 and model=1.12;label +;select atomno=10 and model=1.13;label +;select atomno=10 and model=1.14;label +;select atomno=10 and model=1.15;label +;select atomno=10 and model=1.16;label +;select atomno=10 and model=1.17;label +;select atomno=10 and model=1.18;label +;select atomno=10 and model=1.19;label +;select atomno=10 and model=1.20;label +;select atomno=10 and model=1.21;label +;select atomno=10 and model=1.22;label +;select atomno=2 and model=1.31;label +;select atomno=2 and model=1.32;label +;select atomno=2 and model=1.33;label +;select atomno=2 and model=1.34;label +;select atomno=2 and model=1.35;label +;select atomno=2 and model=1.36;label +;select atomno=2 and model=1.37;label +;select atomno=2 and model=1.38;label +;select atomno=2 and model=1.39;label +;select atomno=2 and model=1.40;label +;select atomno=2 and model=1.41;label +;select atomno=2 and model=1.42;label +;select atomno=2 and model=1.43;label +;select atomno=2 and model=1.32;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.33;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.34;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.35;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.36;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.37;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.38;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.39;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.40;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.41;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.42;lcaocartoon color translucent purple yellow scale 1.1 create "pz";select atomno=2 and model=1.43;lcaocartoon color translucent purple yellow scale 1.1 create "pz";anim mode once;frame 1; delay 0.5; anim on;set echo bottom center;font echo 16 ariel bold;echo orbital and|C-Si bond aligned ', "View orbital animation"); <area shape="rect" coords="253,8,372,166" href="javascript:Jmol.script(jmolApplet0, 'load ../model/organo_main_group/silicon/vinyl_silanes/e/2.xyz;hide atomno=8 or atomno=9 or atomno=10 or atomno=12 or atomno=17 or atomno=18 or atomno=19 or atomno=20 or atomno=21 or atomno=22 or atomno=23 or atomno=24 or atomno=25 or atomno=26 or atomno=27 or atomno=28 or atomno=29 or atomno=30 or atomno=31;wireframe 0.1;spacefill 20%;moveto 0.0 617 726 302 156.91;select all;set labelOffset 0 0;font label 18 ariel bold;color label black;connect (atomno=5) (atomno=6) DOUBLE;connect 1.32 1.35 (atomno=1) (atomno=2) AROMATIC;connect 0.5 1.32 (atomno=1) (atomno=2) DOUBLE;connect 2.31 2.91 (atomno=2) (atomno=4) PARTIAL;connect 2.61 3.07 (atomno=4) (atomno=16) PARTIAL;wireframe 0.1;select atomno=3;label R1;select atomno=11;label R2;select atomno=1 and model=1.1;label +;select atomno=1 and model=1.2;label +;select atomno=1 and model=1.3;label +;select atomno=1 and model=1.4;label +;select atomno=16 and model=1.1;label -;select atomno=16 and model=1.2;label -;select atomno=16 and model=1.3;label -;select atomno=16 and model=1.4;label -;draw arrow1 ARROW {4.108603 1.1507149 -0.7142334} {3.269663 1.5022888 -0.92435265} {2.3494143 1.306509 -0.75275993} {1.5513563 0.5469322 -0.18323898};draw arrow2 ARROW {0.12224674 0.18623638 0.11105728} {0.215765 -0.29528618 -0.13397217} {-0.111652374 -0.6999264 -0.21386337} {-0.79081345 -0.73991966 -0.018016815};draw fill noMesh noDots notFrontOnly fullylit;color draw opaque [xffa500];set echo bottom center;font echo 16 ariel bold;echo correctly aligned;')" /> <area shape="rect" coords="374,55,501,105" href="javascript:Jmol.script(jmolApplet0, 'load ../model/organo_main_group/silicon/vinyl_silanes/e/2.xyz;hide atomno=8 or atomno=9 or atomno=10 or atomno=12 or atomno=17 or atomno=18 or atomno=19 or atomno=20 or atomno=21 or atomno=22 or atomno=23 or atomno=24 or atomno=25 or atomno=26 or atomno=27 or atomno=28 or atomno=29 or atomno=30 or atomno=31;wireframe 0.1;spacefill 20%;moveto 0.0 617 726 302 156.91;select all;set labelOffset 0 0;font label 18 ariel bold;color label black;connect (atomno=5) (atomno=6) DOUBLE;connect 1.32 1.35 (atomno=1) (atomno=2) AROMATIC;connect 0.5 1.32 (atomno=1) (atomno=2) DOUBLE;connect 2.31 2.91 (atomno=2) (atomno=4) PARTIAL;connect 2.61 3.07 (atomno=4) (atomno=16) PARTIAL;wireframe 0.1;select atomno=3;label R1;select atomno=11;label R2;select atomno=1 and model=1.1;label +;select atomno=1 and model=1.2;label +;select atomno=1 and model=1.3;label +;select atomno=1 and model=1.4;label +;select atomno=16 and model=1.1;label -;select atomno=16 and model=1.2;label -;select atomno=16 and model=1.3;label -;select atomno=16 and model=1.4;label -;anim mode once;frame 1; delay 0.5; anim on;set echo bottom center;font echo 16 sansserif bold;echo Plays once through, then stops;')" /> <area shape="rect" coords="503,41,621,134" href="javascript:Jmol.script(jmolApplet0, 'load ../model/organo_main_group/silicon/vinyl_silanes/e/2.xyz;hide atomno=8 or atomno=9 or atomno=10 or atomno=12 or atomno=17 or atomno=18 or atomno=19 or atomno=20 or atomno=21 or atomno=22 or atomno=23 or atomno=24 or atomno=25 or atomno=26 or atomno=27 or atomno=28 or atomno=29 or atomno=30 or atomno=31;frame 30;wireframe 0.1;spacefill 20%;moveto 0.0 617 726 302 156.91;select all;set labelOffset 0 0;font label 18 ariel bold;color label black;connect (atomno=5) (atomno=6) DOUBLE;connect 1.32 1.35 (atomno=1) (atomno=2) AROMATIC;connect 0.5 1.32 (atomno=1) (atomno=2) DOUBLE;connect 2.31 2.91 (atomno=2) (atomno=4) PARTIAL;connect 2.61 3.07 (atomno=4) (atomno=16) PARTIAL;wireframe 0.1;select atomno=3;label R1;select atomno=11;label R2;select atomno=1 and model=1.1;label +;select atomno=1 and model=1.2;label +;select atomno=1 and model=1.3;label +;select atomno=1 and model=1.4;label +;select atomno=16 and model=1.1;label -;select atomno=16 and model=1.2;label -;select atomno=16 and model=1.3;label -;select atomno=16 and model=1.4;label -;')" />

In principle, the alkene could react with the electrophile at either end but reaction next to silicon leads to the more stable cation β to silicon. In the vinyl silane, the C-Si bond is orthogonal to the p orbital of the π bond, but as the electrophile attacks, the silyl group starts to move upwards, increasing the interaction between the C-Si bond and the empty p orbital of the cation. Rotation is restricted and the C-Si bond stabilization is decreased, resulting in the quick removal of the silyl group to form the alkene which retains its geometry.

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I. Fleming, A. Barbero and D. Walter, Chem. Rev., 1997, 97, 2063–2192.

 

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