Chemistry of siloles. The reactions of siloles with organolithium reagents

Reactions of dilithiobutadienes with monochlorosilanes: Observation of facile loss of organic groups from silicon

“…The assignment of silole 9b was based on the mass spectrum, and on the 1 H NMR spectrum (CDCl 3 ) which was comparable to that reported [10] (in CCl 4 ); in particular the SiMe of 9b was found at d 0.72 (this work) and d 0.71 (reported).…”

“…In 1983, Ishikawa and co-workers reported that several dibenzosiloles, including 9a, react with organolithium reagents to form products of exchange of alkyl groups on the silicon, and they proposed a pentacoordinate organosilicate intermediate [10,15]. Klumpp and co-workers were the first to observe an intermediate of this type by NMR [12a,12b].…”

“…The region between d 0.27 and 0.9 in the 1 H NMR contained major peaks at d 0.27 (PhMe 2 Sit-Bu, 0.42 (9a), 0.55 (10c), and 0.88 (PhMe 2 Si-t-Bu) and a smaller peak at 0.73 (9b). The peak at 0.73 was assigned as 9b based on the fact the presence of 9b was indicated by the GC/MS (below), isolation of 9b from an analogous reaction mixture in 71% GC purity (below), and the reported [10] NMR shift for MeSi in 9b (d 0.71 in CCl 4 ).…”

“…The peak at 7.7 min showed m/z 192 (3, M + ), 135 (100, PhMe 2 Si + ), 105 (5, PhSi + ), and was assigned as phenyldimethyl-tert-butylsilane (presumably from excess t-BuLi and PhMe 2 SiCl). The peak at 13.4 min showed m/z 272 (48, M + ) and 257 (100, M + À Me), and was assigned as 1-methyl-1-phenyldibenzosilole (9b) [10]. A number of very small peaks were present including one at 8.7 min which corresponded to biphenyl [28], and one at 10.6 min which corresponded to siloxane 11c [28].…”

The Superbase‐Mediated Pairwise Substitution of the 2,2′‐ and 6,6′‐Positions in a Biphenyl Derivative

“…4,4Ј-Di-tert-butylbenzene, a commercial product, was dissolved in hexanes and treated for 12 h at ϩ70°C with two molar equivalents of butyllithium and potassium tertbutoxide before the reaction was quenched with dichlorodimethylsilane to afford the 2,7-di-tert-butyl-9,9-dimethyl-9-silafluorene [4] (1; 72%). Trapping of the intermediate with carbon dioxide followed by neutralization gave 2,2Ј-biphenyldicarboxylic acid [5] (2a; 53%) and 2,7-di-tert-butylfluor- [a] enone [6] (4; 15%), but no 2-biphenylylcarboxylic acid (3a, independently prepared from the monoiodobiphenyl 3c) at all.…”