Synthesis of fluorosilylenolates, aminosilylenolates, -ethers, and aldol condensates

Abstract

Depending on the reaction conditions, ketones react with n-BuLi, tert-BuLi or lithium diisopropylamide to give enolates or alcoholates. In the reaction of tert-butylmethylketone with n-BuLi followed by fluorosilanes, the fluorosilyl-enolates H2C=C(O-SiFRR')CMe3 (1-4) and fluorosilylethers Me3C(CH3)(n-C4H9)C-0-SiFRR' (5 - 8) [R, R' = Me (1, 5); F, CMe3 (2, 6); F, C6H5 (3, 7); F. CHMe,) (4, 8)] are formed. Using tert-butylmethylketone, n-BuLi and (Me3C)(2)SiF2, isobutene and the fluorosilyl-enolate of acetaldehyde H2C=CH-0-SiF(CMe3)2 (9) are obtained. Diisopropylketone reacts with Me3CLi and fluorosilanes to give the fluorosilyl-enolates Me2C=C(O-SiFRR')CHMe2 (10, 11) and -ethers, Me3C(Me2HC)(2)C-0-SiFRR' (12, 13) [R, R' = Me (10, 11); F, CMe3 (12, 13)] whereas only the silylethers R(Me)(C6H5)C-0-SiFRR' [R, R, R" = n-C4H9, Me, Me (14); C6H5, F, Me (15)] are generated in the reaction of H3 C(C6H5)C=O with lithium-alkyls and fluorosilanes. I Di(tei-t-butyl)fluorosiloxy-1-cyclohexene (16) is the product of the reaction of lithiated cyclohexanone and (Me3C)(2)SiF2. A side reaction of the enolate formation is often a condensation releasing water. For that reason, acyclic and cyclic siloxanes may appear as by-products, e. g. disiloxane (17) using (Me3C)(2)SiF,), cyclotrisiloxane (Me3C(C6H5)Si-0)(3) (18) using Me3(C6H5)SiF2, or cyclotetrasiloxane (Me3CSiF-0)4 (19) using Me3CSiF3 in these reactions. Attempts to prepare the enolate of cyclopentanone in the reaction with lithium diisopropylamide lead to the formation of 2,5-dicyclopentylidenepentanone (20). The 3,5,7-triphenyl-3-methyl-4,6-hexadienephenone (21) is an aldol condensate of Me(C6H5)CO. Lithium-tei-t-butylmethylenolate reacts with fluorosilyl-enolates 1 - 3 or SiF4 to give bis(enolato)silanes, (H2C=C(CMe3)0-)(2)SiRR' [R, R' = Me (22); F, CMC3 (23); F, C61-15 (24);] and the tris(enolato)silanes (H2C=C(CMe3)0-)(3)SiR [R = C6H5 (25); F (26)]. Arninosilyl-enolates H7C=C(O-SiR'R"-NHR)CMe3 are obtained in reactions of fluorosilyl-enolates with lithium amide 127: R= CMC3, R'= Me, R"= Me; 28: R= C6H5, R'= F, R"= CMe(3)j. Results of the crystal structure determinations of 17. the cis-isomer of 18, one trans-isomer of 19, the pentanone 20, and the hexadienephenone 21 are reported.