Organomagnesium adducts with

In other cases, however, the initial adduct is stable, and its hydrolysis product is isolable, and is a useful intermediate for further transformations. For example, the products from reactions of organomagnesium compounds with p-oxoketene dithioacetals may be transformed into a variety of... 

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... 

Organolithium and organomagnesium reagents are highly reactive toward most carbonyl compounds. With aldehydes and ketones, the tetrahedral adduct is stable, and alcohols are isolated after protonation of the adduct, which is an alkoxide ion. 

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 . 

Chiral aminals 1,4-dihydropyridine-3-carboxaldehydes.1 The chiral aminal 2 prepared from pyridine-3-carboxylaldehyde and (S,S)-12 reacts with organocopper reagents in the presence of methyl chloroformate to give almost exclusively products of 1,4-addition, as expected from reactions of the free aldehyde.3 No products of 1,2-addition are formed, but 1,6-adducts are minor products in some cases. The 1,4-adducts are formed in 82-93% de (R-configuration). Addition of butyl and ethyl groups is best effected with lithium cuprates, but addition of methyl, vinyl, or aryl groups is best effected with organomagnesium cuprates. Under these conditions,... 

Recently, three research groups independently disclosed that benzotriazoles 18 attached through various linkers to a polymeric support react with aldehydes and amines to form polymer-anchored Mannich-type adducts 19 (Scheme 7) [29]. These intermediates are cleaved under reducing conditions and in the presence of organomagnesium or organozinc reagents to provide libraries of secondary and tertiary amines in moderate yield (11-65%) and with acceptable purity (13->99%) [29]. 

The same classes of organomagnesium compound tend to react carbophilically with dithioesters [4]. An important difference from the corresponding reactions of carboxylic esters is that the initial adducts are much more stable, and can be trapped, as in the following... 

Addition reactions. a,0-Unsaturated carbonyl compounds 1 and 3 undergo exclusive 1,4-addition reactions with organolithium (and organomagnesium) compounds owing to steric hindrance of the carbonyl group. The adducts 2 and 4 are converted into carboxylic acids by cleavage with potassium t-butoxide and H2O in the case of 2 see potassium r-hutoxidc, this volume) and by treatment with ethanolic... 

Tetraphenyltitanium may also be prepared by reacting an organomagnesium reagent, preferably with an adduct of the TiX4, such as TiCl4(py)2... 

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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