Grignard reagents carbonyl compounds

As examples of their addition to carbonyl compounds, Grignard reagents react with formaldehyde, H2C = 0, to give primary alcohols, with aldehydes to give secondary alcohols, and with ketones to give tertiary alcohols. 

Which alcohol can be formed by three different combinations of carbonyl compound + Grignard reagent ... 

In addition to reacting with aldehydes and ketones—Class II carbonyl compounds— Grignard reagents react with Class I carbonyl compounds—carbonyl compounds that have groups that can be replaced by another group. 

In a method which may only be applicable to the preparation of benzylic carbonyl compounds, Grignard reagents (stereospecifically) transform methyl-sulphinyl derivatives (7) into the anion [equation (6)]. Other than protonation, no further transformations of the arylacetaldehyde derivatives were described. 

The a-halo carbonyl compounds are reagents for the synthon +C-C=0. At a lower oxidation level, epoxides are reagents for the synthons +C-C=0 as in their reaction with Grignard or organolithium reagents (see also frames 162-6). 

COUPLING OF ALLYLIC COMPOUNDS Dimethylcopperlithium. Iron. Nickel carbonyl. Trimethylironlithium. GRIGNARD REAGENTS Thallium(I)-bromide. 

Reaction of an ester with a Grignard reagent involves the alcohol containing the two identical alkyl groups from the formation of two successive tetrahedral carbonyl addi- Grignard reagent, tion compounds. The result of the overall reaction is an... 

Traditionally, it is the addition of organomagnesium compounds (Grignard reagents) to carbonyl compounds to generate alcohols. A more modern interpretation extends the scope of the reaction to include the addition of Grignard reagents to a wide variety of electrophilic substrates ... 

In a newly developed electrochemical Grignard-type allylation of carbonyl compounds allyltin reagents are said to be recycled [122]. 

The main use of organocadmium compounds is for the preparation of ketones and keto-esters, and their special merit lies in the fact that they react vigorously with acid chlorides of all types but add sluggishly or not at all to multiple bonds (compare addition of Grignard reagents to carbonyl groups). Some t3rpical syntheses are ... 

The anion B is just the enolate anion of a carbonyl compound, actually the same as A. So there is no need to use a Grignard reagent or any other synthetic equivalent in this reaction anion B itself can be the intermediate and we simply treat the aldehyde with mild base ... 

The mam synthetic application of Grignard reagents is their reaction with certain carbonyl containing compounds to produce alcohols Carbon-carbon bond formation is rapid and exothermic when a Grignard reagent reacts with an aldehyde or ketone... 

The type of alcohol produced depends on the carbonyl compound Substituents present on the carbonyl group of an aldehyde or ketone stay there—they become sub stituents on the carbon that bears the hydroxyl group m the product Thus as shown m Table 14 3 (following page) formaldehyde reacts with Grignard reagents to yield pri mary alcohols aldehydes yield secondary alcohols and ketones yield tertiary alcohols... 

Sodium borohydride and lithium aluminum hydride react with carbonyl compounds in much the same way that Grignard reagents do except that they function as hydride donors rather than as carbanion sources Figure 15 2 outlines the general mechanism for the sodium borohydride reduction of an aldehyde or ketone (R2C=0) Two points are especially important about this process... 

Cyclic Peroxides. CycHc diperoxides (4) and triperoxides (5) are soHds and the low molecular weight compounds are shock-sensitive and explosive (151). The melting points of some characteristic compounds of this type are given in Table 5. They can be reduced to carbonyl compounds and alcohols with zinc and alkaH, zinc and acetic acid, aluminum amalgam, Grignard reagents, and warm acidified iodides (44,122). They are more difficult to analyze by titration with acidified iodides than the acycHc peroxides and have been sucessfuUy analyzed by gas chromatography (112). 

In equation 1, the Grignard reagent, C H MgBr, plays a dual role as reducing agent and the source of the arene compound (see Grignard reaction). The Cr(CO)g is recovered from an apparent phenyl chromium intermediate by the addition of water (19,20). Other routes to chromium hexacarbonyl are possible, and an excellent summary of chromium carbonyl and derivatives can be found in reference 2. The only access to the less stable Cr(—II) and Cr(—I) oxidation states is by reduction of Cr(CO)g. 

The reaction involves nucleophilic substitution of for OR and addition of R MgX to the carbonyl group. With 1,4-dimagnesium compounds, esters are converted to cyclopentanols (40). Lactones react with Grignard reagents and give diols as products. 

Alcohol synthesis via the reaction of Grignard reagents with carbonyl compounds (Section 14.6) This is one of the... 

There has been recent interest in naphtho-fused dithiepines as chiral acyl anion equivalents, particularly since the starting dithiol 128 can be obtained in enan-tiomerically pure form (89TL2575). This is transformed using standard methods into the dithiepine 129, but showed only moderate diastereoselectivity in its addition to carbonyl compounds. On the other hand, as we have seen previously for other systems, formation of the 2-acyl compound 130 and reduction or addition of a Grignard reagent gave the products 131 with much better stereoselectivity (91JOC4467). 

Grignard reagents that contain a /3-hydrogen—e.g. 15—can reduce a carbonyl substrate by transfer of that hydrogen as a side-reaction. The so-called Grignard reduction is likely to proceed via a six-membered cyclic transition state 16 the alkyl group of alkylmagnesium compound 15 is thereby converted into an alkene 17. 

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