Preparation Grignard-type addition

There are few reports of oxidative addition to zerovalent transition metals under mild conditions three reports involving group 10 elements have appeared. Fischer and Burger reported the preparation of aTT -allylpalladium complex by the reaction of palladium sponge with allyl bromide(63). The Grignard-type addition of allyl halides to aldehydes has been carried out by reacting allylic halides with cobalt or nickel metal prepared by reduction of cobalt or nickel halides with manganese/iron alloy-thiourea(64). 

The development of the Grignard-type addition to carbonyl compounds mediated by transition metals would be of interest as the compatibility with a variety of functionality would be expected under the reaction conditions employed. One example has been reported on the addition of allyl halides to aldehydes in the presence of cobalt or nickel metal however, yields were low (up to 22%). Benzylic nickel halides prepared in situ by the oxidative addition of benzyl halides to metallic nickel were found to add to benzil and give the corresponding 3-hydroxyketones in high yields(46). The reaction appears to be quite general and will tolerate a wide range of functionality. 

Lactone products can also be formed via Grignard-type addition to aldehydes from o-iodobenzoates [116]. The Cheng group developed an enantioselective Co-catalyzed method for preparation of 5-membered phthalide products from methyl o-iodobenzoate and aldehydes (Scheme 2.61). While Ni and Pd catalysts were ineffective, the authors propose a Co(I)/Co(III) mechanism involving oxidative addition of the sp C—I bond followed by addition and ring closure [116]. Co(III) is reduced to Co(I) by the zinc metal present in solution. 

We reported that smooth oxidative addition of organic halides such as aryl, benzyl, and allyl halides to metallic nickel proceeded to afford organonickel halides under mild conditions, which yielded homocoupled products [11, 41] or ketones by the reaction with acid chlorides [42] or alkyl oxalyl chlorides [43]. We describe here a new method for the preparation of 3-aryl-2-hydroxy-l-propanones (4) in good yield by the Grignard-type addition of benzyl halides to 1,2-diketones mediated by metallic nickel under neutral conditions [44]. 

Orgcuiochromium compounds prepared from halides and Cr(II) species in anhydrous, aprotic, polar solvents provide means of selective synthesis as has been described previously (, ). In particular, the Grignard type carbonyl addition of cdlylchromium reagents proceeds much more slowly and selectively than that of orgcuiomagnesium compounds. 

TT-Benzyl complexes typically form when a benzyl group is present in a coordina-tively unsaturated middle or late metal center that can participate in back-donation into the TT-benzyl urut. TT-Benzyl complexes have been prepared by the addition of benzyl Grignard reagents to unsaturated metal-halide complexes, by the addition of benzyl halides to low-valent metal complexes, or by the insertion of vinylarenes into metal hydrides or alkyls. These three types of reactions are illustrated by the examples in Equations 3.70-3.72. 

The nucleophilic addition reaction is the most common general reaction type for aldehydes and ketones. Many different kinds of products can be prepared by nucleophilic additions. Aldehydes and ketones are reduced by NaBH4 or UAIH4 to yield primary and secondary alcohols, respectively. Addition of Grignard reagents to aldehydes and ketones also gives alcohols (secondary and tertiary, respectively), and addition of HCN delds cyanohydrins. Primary amines add to carbonyl compounds yielding imines, or Schiff bases, and secondary... 

The main use of organocadmium compounds is for the preparation of ketones and keto-esters, and their special merit lies in the fact that they react vigorously with acid chlorides of all types but add sluggishly or not at all to multiple bonds (compare addition of Grignard reagents to carbonyl groups). Some t3rpical syntheses are ... 

This type of reaction involves both oxidation and addition of groups, so it is known as an oxad reaction. Alkyl derivatives of PC13 can be prepared by the reactions with Grignard reagents and metal alkyls illustrated in the following equations ... 

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