Reaction with Organomagnesium Amide

TABLE 1. Stmcturally characterized organomagnesium amides synthesized from the reaction of amines or metal amides with diorganomagnesium precursors... 

O-Benzyllactaldehyde dimethylhydrazone 230 allows a substrate control in the addition reaction of organomagnesium halides, leading almost exclusively to the 5yn-isomer 231 (equation 155) . The resulting hydrazide can be reduced on Raney Ni to the corresponding iyw-aminoalcohol 232. The stereoselective Grignard addition to a similar A-formyl hydrazone 233 proceeds with 92% diastereoselectivity (equation 156). The silylation of the amide nitrogen by TMSCl provides the pure iyw-adduct . 

Similar considerations apply to reactions of organomagnesium compounds with formate esters (leading to aldehydes), chloroformates or carbonates (leading to esters) or carbamoyl chlorides (leading to amides) ... 

Reactions of organomagnesium compounds with /V,/V-disubstituted amides differ from those of other acyl derivatives (Section 6.2) in that the initial adducts are much more stable. However, although examples are known where a carbinolamine may be isolated following careful hydrolysis, acid hydrolysis without special precautions usually gives the... 

The usual reactions of organomagnesium compounds with esters, amides and nitriles are those described in Sections 5.3, 6.2 and 6.3. However, factors such as steric hindrance and stability of leaving group may lead to reactions resulting in overall nucleophilic displacement. Most of them are of limited applicability (see Ref. [39] for examples involving carbamate), but two warrant coverage. 

Addition of an organomagnesium bond to an alkene, alkyne, or a benzenoid ring generates a new organomagnesium compound. With simple alkenes, addition occurs only under strenuous conditions. This reaction will be discussed later, with appropriate examples, as a reaction of organomagnesium compounds in the Section on Amides and Lactans.. 

In contrast with conjugated ketones and esters, the reaction between conjugated amides and all types of RMgX proceeds through a 1,4-addition [1-4], particularly with the allylic [21,22] and allenylic [6] organomagnesium derivatives [Eq. (7)] ... 

A simple synthetic route to compounds of the type R Mg(NR R ) is the reaction of equimolar amounts of MgR and a secondary amine, HNR R . By this method sterically hindered 1,3,6,8-tetra-t-butylcarbazole and diethylmagnesium in THF afford 52 as the bistetrahydrofuran adduct, and hexamethyldisilazane (HN(TMS)2) and "BuMg Bu in heptane form nonsolvated 53 [23]. Metalation of activated G-H groups by the amide bases Mg(TMP)2 (TMPH = 2,2,6,6-tetramethylpiperidine) or Mg(N Pr2)2 can also produce organomagnesium amides. Reactions of metal amide (MNR R (M = Li or Na)) with the appropriate Grignard reagent have been used to produce 54 [24] and 55 [25] (Scheme 3.31). 

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