Grignard reagents addition with

Additionally, Grignard reagent reacts with an alkyl orthoformate to form an acetal which is then hydrolyzed to the corresponding aldehyde usiag dilute acid. 

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. 

The fact that only Grignard reagents add with high diastereoselectivity to the phenylmenthyl ester of glyoxylic acid, whereas methyllithium reacts nonstereoselectively, may be the result of a different aggregation of the reagents. This is supported by the tremendous improvement of the stereoselectivity when the addition of methyllithium is undertaken in the presence of lithium perchlorate13. 

The low yields, which are observed among styrenyl adducts, reflect a combination of the poor reactivity of the styrene at the low temperature of the reaction. For example, the combination of t-butyl Grignard with the 2,4-bis-OBoc-benzyl alcohol 15 affords the corresponding benzopyran 50 in only 50% yield even when carried out in the presence of 5-10 equivalents of the styrene (method H, Fig. 4.27).27 Yields for substituted benzopyran styrene adducts are still lower (method G, Fig. 4.27). For example, addition of methyl lithium to 2,4-bis-OBoc-benzylaldehyde 5 followed by the addition of the dienophile and magnesium bromide affords benzopyran 51 in a paltry 27% yield. Method F is entirely ineffective in these cases, because the methyl Grignard reagent competes with the enol ether and with styrene 1,4-addition of methyl supercedes cycloaddition. 

A high level of activity continues in connection with the synthesis of antimalarial artemisinin analogues and congeners, in which the 1,2-dioxepane moiety is embedded. Recent examples include the syntheses of various 10-substituted deoxoartemisinins of type 123 (eg. R1 = Cl COMe) from dihydroartemisinin acetate, and of type 124 (eg. R2 = a-OH, R3 = Me), from Grignard reagent addition to 10-(2-oxoethyl)deoxoartemisinin . 

Asymmetric addition of Grignard reagents to CJfflHO.1 Grignard reagents pretreated with (-)-l at -78° add to benzaldehyde with only slight enantiose-lectivity ( 20% ee). But if the addition is effected in the presence of 2,4,6-tri-methylphenoxyaluminum dichloride (2), the carbinol is obtained in 40-70% ee. 

Addition of RMgBr to nitriles. Grignard reagents react with nitriles slowly if at all, but even r-butylmagnesium chloride will add to nitriles in refluxing THF when catalyzed by a copper(I) salt. The adduct can be converted to a ketimine by anhydrous protonation, to a primary amine by reduction (Li/NH,), or to a ketone by hydrolysis. The actual reagent may be a cuprate such as R3Cu(MgX)2. 

Grignard reagents add with difficulty to imines derived from enolizable carbonyl compounds. The activation of the C=N bond can be achieved either by attachment of an electron-with drawing group or A-coordination with a Lewis acid . The use of a catalytic amount of the soluble rare-earth metal complex LnCl3 2LiCl allows the addition of... 

Many years later, Fukuhara and Urabe showed that aryl Grignard reagents react with ethyl 2,4-dienoates or 2,4-dienamides, in the presence of iron salts, to give the 1,6-addition products (Scheme 60). This reaction is stereoselective and leads to the (Z)-trisubstituted olefins. 

Grignard reagent reacts with CO2 to give magnesium salts of carboxylic acid. Addition of aqueous acid produces carboxylic acid. 

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