Organosubstituierte 2,5‐Dihydro‐1,2,5‐oxoniasilaboratole Charakterisierung und Reaktivität

Organosubstituted 2,5‐Dihydro‐1,2,5‐oxoniasilaboratoles – Characterization and Reactivity. The potassium salts of the anions (2 a−d , a : R 2,3 = CH 3 ; b : R 2 = C 2 H 5 , R 3 = CH 3 ; c : R 2 = C 6 H 5 , R 3 = CH 3 ; d : R 3 = C 6 H 5 ), prepared from the organosubstituted cis ;‐2‐boryl‐1‐silylalkenes 1a – d and KOH, react with the electrophiles R 1 Hal [R 1 = H: HCl, (CH 3 ) 3 NHCl; R 1 = CH 3 : (CH 3 )I, (CH 3 ) 4 NCl; or (CH 3 ) 3 El IV (CH 3 ) 3 , El IV =Si, Ge, Sn, Pb] to give the neutral five‐membered ring compounds [R 1 = H: 3 H; CH 3 ; 3 Me; El IV (CH 3 ) 3 : 3 El IV ]. On heating of 3H or 3Sn either ethyl migration occurs to yield the saturated diastereomers ( 4 ) [ 4 / 4 ′: R 3′ = H; 4 Sn/ 4 ′Sn: R 3′ = Sn(CH 3 ) 3 ], or elimination of ethane takes place to give the unsaturated compounds ( 5 ). The reaction of 2 with ClPb(CH 3 ) 3 leads to 3Pb [R 1 =Pb(CH 3 ) 3 ] ( 11 B‐NMR), which exclusively form 5 with elimination of C 2 H 5 Pb(CH 3 ) 3 .