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A solution of a carbonyl compound is added to a Grignard reagent. (See gallery) An example of a Grignard reaction (R 2 or R 3 could be hydrogen). The Grignard reaction (French:) is an organometallic chemical reaction in which, according to the classical definition, carbon alkyl, allyl, vinyl, or aryl magnesium halides (Grignard reagent) are added to the carbonyl groups of either an aldehyde or ...
Less frequently silanols are prepared by oxidation of silyl hydrides, a reaction that uses a metal catalyst: 2 R 3 SiH + O 2 → 2 R 3 SiOH. Many silanols have been isolated including (CH 3) 3 SiOH and (C 6 H 5) 3 SiOH. They are about 500x more acidic than the corresponding alcohols. Siloxides are the deprotonated derivatives of silanols: [22 ...
In acidic conditions, alkyl substituents acting as electron withdrawing groups decrease the reaction rate. [10] As bulker silyl groups are more likely to be electron withdrawing, it is easier to differentiate between less and more bulky silyl groups. [10] Therefore, acidic deprotection occurs fastest for less sterically bulky alkyl silyl groups ...
The increased stability towards acidic hydrolysis and nucleophilic species allows for the TBDPS groups in a substrate to be retained while other silyl ethers are removed. The TMS group may easily be removed in the presence of a TBDPS group by reaction with TsOH. The group is even more resistant to acid hydrolysis than the bulky TIPS.
Trimethylsilylacetylene is commercially available. It may also be prepared in a manner similar to other silyl compounds: deprotonation of acetylene with a Grignard reagent, followed by reaction with trimethylsilyl chloride. [4] Trimethylsilylacetylene is a precursor to 1,4-bis(trimethylsilyl)buta-1,3-diyne, a protected form of 1,3-butadiyne. [5]
To increase the rate of reaction, trimethylsilyl triflate may also be used in the place of trimethylsilyl chloride as a more electrophilic substrate. [ 4 ] [ 5 ] When using an unsymmetrical enolizable carbonyl compound as a substrate, the choice of reaction conditions can help control whether the kinetic or thermodynamic silyl enol ether is ...
The reaction is named for Pierre Bruylants (1855–1950), [2] who first reported it in 1924. [3] The reaction mechanism appears to involve ejection of the nitrile to form an iminium that is then attacked by the Grignard rather than a direct displacement such as an S N 2 reaction.
The major advantage of this method over addition of organometallic reagents to more typical acyl compounds is that it avoids the common problem of over-addition. For these latter reactions, two equivalents of the incoming group add to form an alcohol rather than a ketone or aldehyde. This occurs even if the equivalents of nucleophile are ...