ISSN:
0009-2940
Schlagwort(e):
Silenes
;
Silene dimerization
;
1,2-Disilacyclobutanes
;
2,3-Disilanaphthalene, tetrahydro-
;
Chemistry
;
Inorganic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Tris(trimethylsilyl)silylmagnesium bromide, obtained in situ from tris(trimethylsilyl)silyllithium and magnesium bromide, reacts with acetone, pivalaldehyde, or 2,4,6-trimethylbenzaldehyde to give the (1-hydroxyalkyl)tris(trimethylsilyl)silanes (Me3Si)3SiC(OH)Me2 (1a), (Me3Si)3CH(OH)tBu (1b), and (Me3Si)3SiC(OH)Mes (1c), resp. After deprotonation with methyllithium in ether at -78°C 1a-c eliminate trimethylsilanolate according to a modified Peterson mechanism to form transient silenes (Me3Si)2Si=CR1R2 (6a: R1 = R2 = Me; 6b: R1 = H, R2 = tBu; 6c: R1 = H, R2 = Mes). In the absence of trapping agents these silenes dimerize, 6a leading to the linear dimer 1-isopropenyl-2-isopropyl-1,1,2,2-tetrakis(trimethylsilyl)disilane (7) and 6b giving the head-to-head cyclodimerization product (E)-3,4-di-tert-butyl-1,1,2,2-tetrakis(trimethylsilyl)-1,2-disilacyclobutane (8), whereas 6c in a very unusual cyclodimerization step affords (E)-1,2,3,8a-tetrahydro-1-mesityl-5,7,8a-trimethyl-2,2,3,3-tetrakis(trimethylsilyl)-2,3-disilanaphthalene (9). Compound 9 is the result of an unexpected [2 + 4] reaction, in which the silene formally acts as the monoene and - involving the aromatic substituent - simultaneously also as the diene. The reaction of 1a-c with methyllithium in THF at low temperature initiates 1,3-Si,O-trimethylsilyl migrations leading to (trimethylsiloxy)-[bis(trimethylsilyl)silyl]alkanes (Me3Si)2SiH-CR1R2OSiMe3 3a-c. Reaction of 1a-c with an excess of methyllithium, tert-butyllithium, or phenyllithium, leads to trisilanes (Me3Si)2-SiR3-CHR1R2 11a-e, formed by the addition of the organolithium reagent to the Si=C bond of the transient silences 6a-c. Deprotonation of 1b and 1c in the presence of 2,3-dimethyl-1,3-butadiene gives the [2 + 4] cycloadducts 6-tert-butyl-3,4-dimethyl-1,1-bis(trimethylsilyl)-1-sila-3-cyclohexene (12a) and 6-mesityl-3,4-dimethyl-1,1-bis(trimethylsilyl)-l-sila-3-cyclohexene (12b). For 8 and 9 the results of the X-ray analyses are given.
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/cber.19951280210
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