Mechanistic studies of fluoride-promoted silicon elimination in β-benzotriazolyl-β-aryl-γ-ketosilanes

Novel and Efficient Entry to γ-Aryl-Substituted γ,δ-Unsaturated Ketones, Amides, Nitriles, and Sulfones by Conjugate Additions of 2-Benzotriazolylethylsilanes

“…We now report a novel and straightforward route to γ-aryl-substituted γ,δ-unsaturated ketones, amides, nitriles, and sulfones via conjugate addition of 2-benzotriazolyl-2-arylethylsilanes to α,β-unsaturated compounds. This extends our preliminary results6a which showed that 2-benzotriazolyl-2-arylethylsilanes reagents can be used as masked α-arylalkenyllithium reagents for the synthesis of γ,δ-unsaturated ketones via conjugate addition to 2-cycloalkenones followed by vicinal elimination of trimethylsilyl and benzotriazolyl groups.…”

“…Reagents 6a − c were prepared according to the published procedures in good to excellent yields 6b. Treatment of 6a − c with 1 equiv of n -BuLi at −78 °C in THF, followed by addition of the α,β-unsaturated substrate, afforded the desired products 8a − d (Scheme ) or 11a − d (Scheme ).…”

“…Column chromatography was conducted with silica gel 230−400 mesh. 1-[1-(4-Fluorophenyl)-2-(trimethylsilyl)ethyl]-1 H -1,2,3-benzotriazole ( 6a ),6a 4-[1-(1 H -1,2,3-benzotriazol-1-yl)-2-(trimethylsilyl)ethyl]- N , N -dimethylaniline ( 6b ),6b and 1-[1-phenyl-2-(trimethylsilyl)ethyl]-1 H -1,2,3-benzotriazole ( 6c ) 6b were prepared according to previously reported procedures.…”

Unusual cyclopropanol formation from a β-silyl aldehyde

“…8 When they do react with Lewis or protic acids, they undergo rearrangements, 9 or intramolecular transfer of ligand from the silicon to the carbonyl group, 10 and we know of only one example where a cyclopropanol-forming pathway has been suggested. 11 In parallel with these observations, cyclopropane formation (11 ? 12) is normal with g stannyl carbocations and their precursors, 12 but is unusual with the corresponding silyl compounds, 13 for which rearrangement (13 ?…”

1,2,3-Triazoles

“…When trimethylsilyl derivatives 527 are treated with TFA in dichlorometane, both the trimethylsilyl and benzotriazolyl groups are eliminated to provide 1,2-diarylpropen-1-ones 528 in high yields <1998JOC9983> . Heating of ketones 527 with CsF in DMF yields also propenones 528 , but usually a rearrangement occurs and the corresponding chalcones are the main products <1998J(P2)2515> . Samarium iodide induced removal of benzotriazole from ketones 529 works well with variety of groups R to provide ketones 530 in high yield under mild reaction conditions <1998H(48)1567> .…”