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 (2a−d, a: R2,3 = CH3; b: R2 = C2H5, R3 = CH3; c: R2 = C6H5, R3 = CH3; d: R3 = C6H5), prepared from the organosubstituted cis;‐2‐boryl‐1‐silylalkenes 1a – d and KOH, react with the electrophiles R1Hal [R1 = H: HCl, (CH3)3NHCl; R1 = CH3: (CH3)I, (CH3)4NCl; or (CH3)3ElIV(CH3)3, ElIV=Si, Ge, Sn, Pb] to give the neutral five‐membered ring compounds [R1 = H: 3H; CH3; 3Me; ElIV(CH3)3: 3ElIV]. On heating of 3H or 3Sn either ethyl migration occurs to yield the saturated diastereomers (4) [4/4′: R3′ = H; 4Sn/4′Sn: R3′ = Sn(CH3)3], or elimination of ethane takes place to give the unsaturated compounds (5). The reaction of 2 with ClPb(CH3)3 leads to 3Pb [R1=Pb(CH3)3] (11B‐NMR), which exclusively form 5 with elimination of C2H5Pb(CH3)3.