Grignard reagents conversion

Azolium rings react readily with organometallic compounds. With a Grignard reagent, conversion (193) -> (194) is known in the benzothiazolium series, and 1,3-benzodithioly-liums give products of type (195). 

Step 2a Reaction of an alkyl chloride with magnesium (Mg) provides the corresponding Grignard reagent (conversion of an electrophilic carbon to a nucleophilic carbon). 

The pale yellow colour cannot be removed by redistiUation or recrystal lisation the coloured product probably contains some amino compound rendering it unsuitable for conversion into a Grignard reagent. A pure... 

The conversion of acetylenes into acetyl ides, M-C=C-R (M = Li, Na, K, MgBr), by means of alkyllithium or Grignard reagents in organic solvents or by alkali metal amides in liquid ammonia is well documented (for practical examples see ref. 1, for review articles consult inter alia refs. 2-5). 

Solutions of tert.-butylmagnesium chloride and cyclopentylmagnesium chloride in diethyl ether can be prepared in the same way. In these cases also the purity of the chlorides Is of great importance for a successful and smooth conversion into the Grignard reagent. 

This procedure illustrates a general method for the preparation of 2-hydroxybicyclo[3.2.0]heptanes by copper(I)-catalyzed photobicyclization of 3-hydroxy-1,6-heptadienes, and a general route to the requisite dienes from allyl alcohols by conversion to 4-pentenals and treatment of the latter with vinyl Grignard reagents. 

The reaction of 17-keto steroids with hydrogen cyanide (or acetone cyanohydrin) to form a mixture of the 17-cyano-17-hydroxy compounds, followed by dehydration and reaction with methyl Grignard reagent, is one of the earliest methods for the conversion of androstanes to pregnanes. 

Because 2-chloroethanol has a proton bonded to oxygen, it is not an appropriate substrate for conversion to a stable Grignard reagent. 

The overall conversion of a 2-furyl ketal to a 6-substitutod l-hydroxy-2-pyridone (79) can be effected by electrolysis in methanol followed by reaction with hydroxylamine. A Grignard reagent can... 

The conversion of a 4-arylazo-5-oxazolone into a 1,2,4-triazole by reaction with a Grignard reagent is mentioned in Section II, B, 3. In HiTnilar fashion, the rearrangement of compound 30 to derivatives of 3-carboxy-l,5-diphenyl-lfl -l,2,4-triazoles (40) proceeds readily in the presence of strong nucleophiles [Eq. (26)]. This transformation undoubtedly occurs by ring opening and dehydrative cychzation, and, indeed, the acyclic amide and hydrazide 41 have been isolated. ... 

The conversion of a nitrile R —CN into a ketone R —CO—R demonstrates that polarized multiple bonds other than C=0 also react with Grignard reagents, and that such reactions are synthetically useful. Esters 22 and acid chlorides can react subsequently with two equivalents of RMgX the initially formed tetravalent product from the first addition reaction can decompose to a ketone that is still reactive, and reacts with a second RMgX. The final product 23 then contains two substituents R, coming from the Grignard reagent ... 

An interesting appetite suppressant very distantly related to hexahydroamphetamines is somanta-dine (24). The reported synthesis starts with conversion of 1-adamantanecarboxylic acid (20) via the usual steps to the ester, reduction to the alcohol, transformation to the bromide (21), conversion of the latter to a Grignard reagent with magnesium metal, and transformation to tertiary alcohol 22 by reaction with acetone. Displacement to the fomiamide (23) and hydrolysis to the tertiary amine (24) completes the preparation of somantadine [6]. 

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. 

Prepared in situ by treatment of the corresponding Grignard reagent with 1 equivalent of CuBr (CH3)2S complex. b 51 % conversion. 

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