Alcohols Grignard

All that has been said in this section applies with equal force to the use of organo-lithium reagents in the synthesis of alcohols. Grignard reagents are one source of nucleophilic carbon organolithium reagents are another. Both have substantial carbanionic char acter in their- car bon-metal bonds and undergo the same kind of reaction with aldehydes and ketones. 

Conversion of Esters into Alcohols Grignard Reaction Esters and lactones react with 2 equivalents of a Grignard reagent to yield a tertiary alcohol in which two of the substituents are identical (Section 17.5). The reaction occurs by the usual nucleophilic substitution mechanism to give an intermediate ketone, which reacts further with the Grignard reagent to yield a tertiary alcohol. 

The most common reactions of carboxylic acid derivatives are substitution by water (hydrolysis) to yield an acid, by an alcohol (alcoholysis) to yield an ester, by an amine (aminolysis) to yield an amide, by hydride ion to yield an alcohol (reduction), and by an organometallic reagent to yield an alcohol (Grignard reaction). 

Cyclohexyltrichlorosilane reacts with water, alcohols, Grignard reagents, and amines to give siloxanes, ethers, cyclohexyl-substituted organosilanes, and silylamines, respectively. 

More recently, Yadav [10] has shown that alkylation of propargyl alcohol Grignard with prenyl bromide 7 (bearing a trisubstituted double bond), gave the 8 2 product 8 in... 

Carbodiitnides (332 Scheme 55) form amidines on treatment with NaBH4 in alcohols, Grignard reagents, sodium phenylacetylide, carbon monoxide in the presence of s-butyl- or t-butyl-lithium and nitrones catalyzed by HBF4. In the reaction of stannylated or silylated ynamines with carbodiimides... 

Thus hydroxide ion leads to saponification (p. 231) another alkoxide ion leads to transesterification (p. 231) and carbanions give keto compounds or tertiary alcohols (Grignard reaction). 

The desired building block 204 was obtained by partial reduction of the triple bond in 218, followed by successive protection of the primary alcohol, oxidation of the secondary hydroxy group to the ketone, deprotection of the alcohol, Grignard reaction with vinylmagnesium bromide (65) and acetylation. The C2o-building block 204 was converted, with triphenylphosphine hydrobromide, into the phosphonium salt 219, reaction of which with the Cio-dialdehyde 45 gave C.p. 450 (203) Scheme 48). 

ALLENES Carbon dioxide. Cuprous bromide. Trifluoromethanesulfonic anhydride. a-ALLENIC ALCOHOLS Grignard reagents. 

---