Secondary alcohols formation from Grignard reagent

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. ... 

The addition of Grignard reagents to aldehydes, ketones, and esters is the basis for the synthesis of a wide variety of alcohols, and several examples are given in Scheme 7.3. Primary alcohols can be made from formaldehyde (Entry 1) or, with addition of two carbons, from ethylene oxide (Entry 2). Secondary alcohols are obtained from aldehydes (Entries 3 to 6) or formate esters (Entry 7). Tertiary alcohols can be made from esters (Entries 8 and 9) or ketones (Entry 10). Lactones give diols (Entry 11). Aldehydes can be prepared from trialkyl orthoformate esters (Entries 12 and 13). Ketones can be made from nitriles (Entries 14 and 15), pyridine-2-thiol esters (Entry 16), N-methoxy-A-methyl carboxamides (Entries 17 and 18), or anhydrides (Entry 19). Carboxylic acids are available by reaction with C02 (Entries 20 to 22). Amines can be prepared from imines (Entry 23). Two-step procedures that involve formation and dehydration of alcohols provide routes to certain alkenes (Entries 24 and 25). 

The reaction of aldehydes and ketones with Grignard reagents is a useful method of synthesising primary, secondary, and tertiary alcohols (Following fig.). Primary alcohols can be obtained from formaldehydes, secondary alcohols can be obtained from aldehydes, and tertiary alcohols can be obtained from ketones. The reaction involves the formation of a carbon-carbon bond and so this is an important way of building up complex organic structures from simple starting materials. 

Alcohols react with HX to form alkyl halides, but the reaction works well only for tertiary alcohols, R,COH. Primaiy and secondary alkyl halides are normally prepared from alcohols using either SOClj or PBr ). Alkyl halides react with magnesium in ether solution to form organomagnesium halides, or Grignard ret ents (RM O- Since Grignard reagents are both nucleophilic and basic, they react with acids to yield hydrocarbons. The overall result of Grignard formation and protonation is the conversion of an alkyl halide into an alkane (RX— RM RH). 

In such reactions an olefin is formed from the Grignard reagent. When, however, propylmagnesium bromide is allowed to react with diisopropyl ketone, reduction to the secondary alcohol (63%) is accompanied by normal addition of the Grignard reagent to the carbonyl group with formation of the tertiary alcohol (30%) 185 and if magnesium bromide is added to the reaction mixture the yield of tertiary alcohol is considerably increased (to 65%).185... 

Which of the following secondary alcohols can be prepared from the reaction of methyl formate with excess Grignard reagent ... 

Formation of a Secondary Alcohol from a Grignard Reagent and an Aldehyde... 

Grignard reagents add twice to give tertiary alcohols (or secondary alcohols, from formates). Lithium aluminum hydride reduces esters all the way to alcohols, whereas bis(2-methylpropyl)aluminum (diisobutylaluminum) hydride allows the process to be stopped at the aldehyde stage. With LDA, it is possible to form ester enolates, which can be alkylated by electrophiles. 

---