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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 ...
Usually Grignard reagents are written as R-Mg-X, but in fact the magnesium(II) centre is tetrahedral when dissolved in Lewis basic solvents, as shown here for the bis-adduct of methylmagnesium chloride and THF. Grignard reagents or Grignard compounds are chemical compounds with the general formula R−Mg−X, where X is a halogen and R is an ...
In the original paper describing this reaction, methylmagnesium bromide is reacted with isophorone with and without 1 mole percent of added copper(I) chloride (see figure). [10] Without added salt the main products are alcohol B (42%) from nucleophilic addition to the carbonyl group and diene C (48%) as its dehydration reaction product.
The silyl group is a non-polar and relatively unreactive species and is therefore tolerant of many reagents and reaction conditions that might be incompatible with free alcohols. Consequently, the silyl group also eliminates the need for introduction of hydroxyl protecting groups. In short, by deferring introduction of an alcohol to a late ...
This feature is exploited in many reactions such as the Sakurai reaction, the Brook rearrangement, the Fleming–Tamao oxidation, and the Peterson olefination. [16] The Si–C bond (1.89 Å) is significantly longer than a typical C–C bond (1.54 Å), suggesting that silyl substitutents have less steric demand than their organyl analogues.
The products after silylation, namely silyl ethers and silyl amines, are resilient toward basic conditions. [2] Protection is typically done by reacting the functional group with a silyl halide by an SN2 reaction mechanism, typically in the presence of base. [3] The protection mechanism begins with the base deprotonating the alcohol group.
The original reaction involved two subsequent substitutions: the conversion of an acid chloride with N,O-dimethylhydroxylamine, to form a Weinreb–Nahm amide, and subsequent treatment of this species with an organometallic reagent such as a Grignard reagent or organolithium reagent.
The conversion is similar to the Grignard reaction. The organozinc reagent is generated via an oxidative addition into the alkyl halide. The reaction produces a primary, secondary, or tertiary alcohol via a 1,2-addition. The Barbier reaction is advantageous because it is a one-pot process: the organozinc reagent is generated in the presence of ...