Grignard-type reaction addition

There are few reports of oxidative addition of metallic transition metals under mild conditions [120] two reports involving group 8 elements have appeared. Fischer and Burger reported the preparation of the n -allylpalladium complex by the reaction of a palladium sponge with allyl bromide [121]. The Grignard-type reaction addition of allyl haUdes 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 [122]. 

Diels-Alder adduct from cyclopentadiene, 8 222t Diels-Alder reactions of, 25 488-489 economic aspects of, 25 507-509 electrophilic addition of, 25 490 in ene reactions, 25 490 esterification of, 25 491 free-radical reactions of, 25 491 from butadiene, 4 371 Grignard-type reactions of, 25 491 halogenation of, 15 491—492 health and safety factors related to, 25 510-511... 

The allylation of imines with allylindium reagents in organic solvents gives the corresponding homoallylic amines.251-253 Under solvent-free conditions, the indium-mediated reaction of iV-benzylideneaniline furnishes a mixture of mono-allylated 79 and bis-allylated products 80 (Equation (56)). The bis-allylated product 80 presumably arises via a formation of an iminium salt, which is subsequently attacked by the allylindium nucleophiles. Formation of 80 is entirely suppressed by addition of allyl bromide to indium metal prior to any addition of the imine (Grignard-type reaction).254... 

Stereoselective catalysis in zeolites is still one of the ultimate goals in zeolite science. Earlier work in this field was summarized recently [4]. More recently, Mahrwald et al. [95] reported that the addition of aluminophosphate molecular sieves in the liquid phase alkylation of a-chiral benzaldehydes by butyllithium results in an increased proportion of the so-called Cram product in the diastereomeric mixture. It is argued that in this Grignard type reaction the adsorption of the reactants on the molecular sieves favors the attack at the sterically less hindered position of the molecule. This shape selectivity effect is even observed when the reactant is adsorbed at the outer crystal surface, as demonstrated for the case of the small-pore AIPO4-I7. 

Recently Yamamoto reported Pd-catalyzed intramolecular nucleophilic addition of the arylpalladium bromide 72 formed from 71 to ketone to give the alcohol 73 using PCy3 as a ligand and an excess of 1-hexanol. This is the first example of a Pd-catalyzed Grignard-type reaction [46],... 

Furthermore, as a related reaction, they obtained the cyclopentanol 79 by the Grignard-type reaction of l-methyl-2-(o-bromophenyl)ethyl phenyl ketone (78) without alkynes in the presence of Pd(OAc)2, PCy3, Na2C03 and 1-hexanol. It was confirmed that the addition of 1-hexanol was crucial [26]. These reactions are mechanistically interesting. A similar catalytic reaction has been reported by Vieente. These reactions are considered again in Chapter 3.7.2 [27]. 

For the mechanism of the metal-mediated Grignard-type reactions in water, Li previously proposed a carbanion/allylmetal/radical triad, in which the specific mechanism of the reaction is dependent on the metal being used (Fig. 4.6). Recently, mechanistic studies of the aUylation detected secondary deuterium kinetic isotope effects in the metal-mediated aUylation ofbenzaldehyde in aqueous media.The inverse SDKIE observed for the indium and tin cases are consistent with the polar addition mechanism. For magnesium and antimony, normal SDKIE were observed. These were interpreted as single electron transfer processes on metal surface in the magnesium case, or between the allyhnetal and the carbonyl compound in the antimony case. 

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. 

Vinylchromium compounds (12,137).6 These compounds can be obtained by reaction of vinyl triflates with CrCl2 catalyzed by NiCl2 in DMF. They undergo selective Grignard-type addition to aldehydes. Some commercial sources of CrCl2 do not require a catalyst, presumably because they contain a metal contaminant. 

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