Grignard reagents with alcohols

Reaction of allylic alcohols with Grignard reagents can occur at the a- or y-position. The site depends in part on the structures of the alcohol and the Grignard reagent y-substitution can be enhanced by addition of HMFI and Cul. 

The coupling of propargyl alcohols with Grignard reagents in the presence of HMPT and Cul provides a useful synthesis of allenes in yields of 60-95%. 

Reaction of allylic alcohols with Grignard reagents. The reaction of n-propyl-magnesium bromide with allylic alcohols in the presence of catalytic amounts of dichlorobis(triphenylphosphine)nickel leads to a mixture of olefins derived from the alcohol 2 for example ... 

Table 3.7. I lydroinaguesiaiiou nt propargyl alcohols with Grignard reagents...

Esters (a) and acid chlorides (6) readily react with Grignard reagents to give ketones, which immediately react with a second equivalent of the reagent as in (5) to give tertiary alcohols as before. 

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... 

In the reaction of aHyl alcohol and Grignard reagent with [P(CgH )2]2-NiCl2 the catalyst, formation of the carbon—carbon bond proceeds at a high yield (22). 

Pyridine undergoes 2- and 4-alkylation with Grignard reagents, depending on whether free metal is present (19). Free metal gives mixtures or exclusive 4-alkylation. Substituent-directed metaHation (eq. 5) has become an important approach to the synthesis of disubstituted pyridines (12). For example, 2- uoro-pyridine [372-48-5] reacts with butyUithium and acetaldehyde to give a 93% yield of alcohol [79527-61-1]. 

Acyl (or 4-hydroxymethylene) isoxazolin-5-ones react with Grignard reagents to give 4-methyleneisoxazolin-5-ones (Scheme 57) 72M141613, 73UC1). In contrast, 4-acylisoxazol-ium salts under the same conditions produced tertiary alcohols (Scheme 57) (75MI41617). 

The cleavage of steroidal epoxides with Grignard reagents leads exclusively to alcohols with the tra 5-diaxial orientation of the hydroxyl group and the newly introduced alkyl group. °... 

Alcohols from Reaction of Carbonyl Compounds with Grignard Reagents 613... 

Esters react with Grignard reagents to yield tertiary alcohols in which two of the substituents bonded to the hydroxyl-bearing carbon have come from the Grignard reagent, just as LiAlH4 reduction of an ester adds two hydrogens. 

Osmium tetroxide, reaction with alkenes, 235-236 toxicity of, 235 Oxalic add, structure of, 753 Oxaloacetic acid, structure of, 753 Oxetane, reaction with Grignard reagents, 680 Oxidation, 233, 348 alcohols, 623-626 aldehydes, 700-701 aldoses, 992-994 alkenes, 233-236 biological, 625-626 phenols, 631 sulfides, 670 thiols, 668... 

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