Aldehydes and Grignard reagents

How can A be broken up so that the structures of the desired aldehyde and Grignard reagent can be deduced Answer A can be broken up in two ways by cleaving the carbon-carbinol carbon bond as illustrated below. 

Boord olefin synthesis. Regiospecific synthesis of olefins from aldehydes and Grignard reagents. 

Further examples of the synthesis of primary amines from oximes, azides, nitriles,isocyanides,aldehydes, and Grignard reagents have also been reported. 

ALDEHYDES FROM 4,4DIMETHYL2 0XAZ0LINE AND GRIGNARD REAGENTS o-ANISALDEHYDE... 

The competition between insertion and hydrogen transfer is also crucial to the selectivity of the reaction of aluminium alkyls with carbonyl compounds. Aluminium alkyls, like organolithium compounds and Grignard reagents, can add to aldehydes and ketones to form secondary or tertiary alcohols, respectively. If the aluminium alkyl has a j -hydrogen, however, reduction of the carbonyl compound is a common side reaction, and can even become the main reaction [16]. Most authors seem to accept that reduction involves direct j5-hydrogen transfer to ketone. 

Halogenopyridines can undergo metal-halogen exchange when treated with butyllithium. The lithium derivatives then behave in a similar manner to arylithiums and Grignard reagents and react with electrophiles such as aldehydes, ketones and nitriles (Scheme 2.17). Thus, aldehydes and ketones form alcohols, and nitriles yield A -lithioimines, which on hydrolysis are converted into pyridyl ketones. 

The great synthetic utility of the reaction of alkyllithium and Grignard reagents with ketonic functions has been well documented.105 These reactions take place via the intermediacy of alkoxy derivatives formed by addition of the M—C bond across the C=0 function. Hence ketones, aldehydes and formaldehyde will lead to tertiary, secondary and primary alkoxides, respectively. This type of reactivity is known for a number of other carbanionic metal alkyl derivatives, both main group and transition metals, although the synthetic utility of the reactivity has in most cases not been well documented. 

The reactions of hydrides and Grignard reagents with simple open-chain aldehydes and ketones 1 (L, M, S, and R being groups containing carbon and hydrogen only) are known to lead predominantly to the diastereoisomers 2 as predicted by Cram s rules (2-4). A modification of the interpretation of these experimental results was published by Cherest, Felkin, and Prudent (5). 

Given the structure of a primary, secondary, or tertiary alcohol, deduce what combination of aldehyde or ketone and Grignard reagent can be used for its synthesis. 

We have seen at least two examples of nucleophilic addition to ketones and aldehydes. A Grignard reagent (a strong nucleophile resembling a carbanion, R= ) attacks the electrophilic carbonyl carbon atom to give an alkoxide intermediate. Subsequent protonation gives an alcohol. 

Acetic formic anhydride has been prepared by the reaction of formic acid with acetic anhydride2 3 and ketene,4,5 and of acetyl chloride with sodium formate.6 The present procedure is essentially that of Muramatsu.6 It is simpler than others previously described and gives better yields. It is easily adapted to the preparation of large quantities, usually with an increase in yield. Acetic formic anhydride is a useful intermediate for the formyl-ation of amines,3,7 amino acids,8,9 and alcohols,2,10 for the synthesis of aldehydes from Grignard reagents,11 and for the preparation of formyl fluoride.12... 

The reaction of ethyl orthoformate and Grignard reagents gives acetals which are hydrolyzed readily by dilute acid to aldehydes. This method has been employed extensively for the preparation of aliphatic and aromatic aldehydes. A study of the optimum conditions has been made, using the conversion of bromobenzene to benzaldehyde as a model synthesis (90%), Comparative studies of various aldehyde syntheses that employ Grignard reagents (methods 154, 166, and 167) show that this one is the most practical however, the possibility of a sudden exothermic reaction limits the size of the run. Longer reaction times at room or reflux tempjerature help overcome this difficulty. Examples of the better preparative procedures are found in those for -hexaldehyde (50%), p-tolualdehyde (TS ), " and phenanthrene-S>-aldehyde (42%)." ... 

N,N-Dialkylformamide or ethyl formate" and Grignard reagents have been used with some success however, the former reaction is complicated and frequently produces tertiary amines as the chief product, and the latte forms secondary alcohols by further reaction of the aldehyde. Substituted benzaldehydes have been prepared from aryllithium compounds and N-methylformanilide in good yields. ... 

Unlike alkyllithium and Grignard reagents, dialkylzinc does not add to ketones even in the presence of (1). Thus the chemo- and enantioselective alkylation of a keto aldehyde (4-benzoylbenzaldehyde) with Et2Zn using (5)-(l) affords the corresponding optically active hydroxy ketone with 93% ee in 99% yield. ... 

CO, BuaSnH, and NCCMe2N=NCMe2CN (AIBN). Aryl ketones can be prepared from aryltrimethylsilanes ArSiMea and acyl chlorides in the presence of AlCla Aryllithium and Grignard reagents react with iron pentacarbonyl to give aldehydes ArCHO. The reaction of CO with aryllithium may occur by electron transfer. ... 

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