1.4- Silyl migrations anionic

Anionic 1,2-silyl migrations from C to O were applied to the [3 + 2] annulations of /J-X-substituted a,/J-unsaturated acylsilanes (X=SPh and SiMe3) 153 with lithium enolates 154,... 

Anionic 1,2-silyl migrations from N to C were found in the reactions of a-silyl amines 179 with s-BuLi (equation 107)241,242. 

Anionic 1,3-silyl migrations across a frameworks with the general formula given in equation 128 are very common and are considered as intramolecular nucleophilic substitutions at silicon312-321. 

Rather exceptional examples of the anionic 1,3-silyl migrations from C to C were reported (equation 133)312,325. 

An anionic 1,4-silyl migration from C to C was observed during the lithiation of 9,10-dihydroanthracene (DHA) derivatives (equation 140)349 - 353. Typically, treatment of DHA 212 (R=SiMe3) with butyllithium followed by hydrolysis gave only ds-9,10-bis(trimethylsilyl)-DHA 213 (R=SiMe3, E=H) stereospecifically. The crossover and deuterium labeling experiments confirmed the intramolecular and irreversible feature of the... 

A 1 1 mixture of (E)- and (Z)-allyloxysilanes 231 was prepared by the reactions of ( )-trimethylsilylvinyl sulfone 229 with aryllithiums followed by the addition of aliphatic aldehydes and cyclohexanone (equation 147). An anionic 1,4-silyl migration from C to O in the lithium alkoxide 230 was proposed to be involved. On the other hand, lithium alkoxide 232 lacking an aryl group was stable and gave no rearranged product even at room temperature (equation 148)360. 

Silyl-substituted carbanions stabilized by heteroatom substituents reacted with epoxides providing the corresponding 3-siloxy carbanions via the anionic 1,4-silyl migrations, which reacted with various electrophiles (equation 149)361-370. 

Anionic 1,4-silyl migrations of O-trialkylsilyl methyl ketoximes (268) were found to give o -trialkylsilyl ketoximes 269 after hydrolysis (equation 167). Intramolecularity of this migration was confirmed by crossover experiments. Upon heating 269 at 100 °C, a reverse migration to 268 took place. The reaction appeared to be limited to silyl ethers of methyl ketoximes having the (E)-configuration413. 

A number of anionic 1,4-silyl migrations between N and N were documented in the review of BB1. Mack and coworkers found a similar N to N migration during the thermal decomposition of an /V.iV-dilithium salt of /V,/V-bis(tri methyl si ly I )ethylenedi amine 297 (equation 184)445. 

Corriu and coworkers found that the reaction of (Z)-y-Af,lV-bis(trhnethylsilyl)amino-1-propenylstannane 298 with butyllithium, followed by quenching with methyl iodide and then hydrolysis, provided 3-methylamino-l-propenylsilane 299 in high yield (equation 185)446, suggesting an anionic 1,4-silyl migration from N to C in the (Z)-vinyllithium 300 to give 301 (equation 186). The transmetallation of the ( )-isomer of 298 gave no silyl migration products (equation 187)447. 

Anionic 1,4-silyl migrations from N to O were also observed in the Dieckman reactions451 and in debenzoylations452. 

An anionic 1,6-silyl migration from C to O (1,6-Brook rearrangement) was observed during the deprotonation of e-silyl alcohol 324, which gave the corresponding silyl ether 325 (equation 199)466. 

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