Grignard reagent silyl

Trialkylsilanes are usually formed by the addition of a lithium or Grignard reagent to the silyl chloride, and thus, discussions related to the formation of the silyl acetylene bond will be kept to a minimum. Silyl acetylenes are prepared from the alkynylcopper(I) reagents in the presence of PPh3, Zn or TMEDA in CH3CN at 100°, 36-98% yield. It is interesting to note that the... 

Silyl-based linker 23, cleaved by either basic (TBAF) or neutral (CsF) fluoridolysis to release carboxylic acids, alcohols, or amines, was prepared by treatment of a Grignard reagent to an aldehyde resin [28], To demonstrate the utility of this handle, /)-bromobenzoic acid was... 

This reaction is extended to the intramolecular ring closure of the intermediate radical 224 with olefinic or trimethylsilylacetylenic side chains [121]. Cu(BF4)2 is also effective as an oxidant (Scheme 89) [122]. Conjugate addition of Grignard reagents to 2-eyclopenten-l-one followed by cyclopropanation of the resulting silyl enol ethers gives the substituted cyclopropyl silyl ethers, which are oxidized to 4-substituted-2-cyclohexen-l-ones according to the above-mentioned method [123]. (Scheme 88 and 89)... 

Unlike alkyl nitronates (302), their silyl analogs react with Grignard reagents at the silicon atom rather than at the a-C atom (306). All these processes may be represented as electrocyclic. 

This work was initiated in 1988 when Villacorta et al.71a reported the asymmetric conjugate addition of a Grignard reagent to 2-cyclohexenone. This study showed that 1,4-adducts with 4-14% ee were obtained in the presence of aminotroponeimine copper complex.713 Enhanced results (74% ee) were obtained by adding HMPA or silyl halides.71b Several other copper complexes were also used for inducing asymmetric conjugate addition reactions. Moderate results were obtained in most cases when THF was used as the solvent and HMPA as the additive. 

Hydraxymethylation. The Grignard reagent (1) prepared from this silyl chloride adds to aldehydes or ketones to provide adducts (2), which undergo oxidative... 

In 1999, Sekiguchi et al. prepared the first silyl acetylene dendrimers 255 and 256 with up to 22 Si atoms and 21 acetylene units (Schemes 35 and 36).358 The preparation of 255 and 256 has been achieved by the reaction of the triple Grignard reagent 257 with the trisila diyne 258 and the heptasila hexayne 259, respectively. 

Various carbon nucleophiles, such as allylsilanes, allylstannanes, silyl enol ethers, ketene silyl acetals, organoaluminum compounds, and Grignard reagents were effective as carbon nucleophiles. 

The presence of the two spirotetrahydrofuran rings in these reactive intermediates is obviously not condudve to the stereocontrolled synthesis of 14. This problem was resolved by making recourse to 22, a precursor to 15, the silyl-protected (3-hydroxypropyl) substituent which was viewed to be sufficiently bulky to guarantee its equatorial occupancy in the lowest energy conformation (Scheme 3-4). Furthermore, treatment of 22 with Grignard reagent should be met with rapid deprotonation of the hydroxyl and formation of chelate 23. At this point, customary equatorial... 

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