In nickel-catalysed reactions

Figure 1.3. Effect of ligands and valence states on the selectivity in the nickel catalysed reaction...

The nickel-catalysed reaction of organomagnesium compounds with dithioacetals, in which the initial substitution leads to elimination, giving a substituted alkene, is potentially useful [23, 24], as in the following procedure. Elimination of [3-alkoxy or alkylthio groups from the... 

In the nickel-catalysed reaction, the use of ligand with only 20% enantiomeric excess still produced a Diels-Alder adduct with up to 96% ee, which is a highly effective example of chiral amplification (see Section 6.1). 

Once again, the nickel-catalysed reactions are far more sensitive to the steric encumbrances, than the palladium-catalysed analogues. Aryl triflates and related sulfonates can serve as the electrophilic reactants in the Kharasch reactions in the presence of an equimolar amount of lithium bromide. The latter additive is a reagent for triflate-bromide exchange, which became a very fast reaction under the Kharasch reaction conditions, since the nickel and palladium-catalysed nucleophilic substitutions of aryl halides and sulfonates are well established reactions, see Chapter 3. In this manner, 2-biphenyl triflate (135) was reacted with 4-tolylmagnesium bromide (136) to give 2-(4-tolyl)biphenyl (137) with a 93% yield [40], respectively. Scheme 8. 

Methylenec clobntanes and 1,2-Bismethylenecyclobutanes.—Further details have appeared of the formation of methylenecyclobutanes in the nickel-catalysed reactions of butadiene with strained cyclic olefins. ... 

There has been a wide-ranging review of transmetalation reactions of arenes concentrating on the use of boron-containing compounds. The reaction of arylboronate esters and related compounds with alkyl halides is catalysed by copper(I) formation of an aryl—copper intermediate followed by an 5N2-type reaction with the alkyl electrophile is likely. Palladium complexed with a diimine is an excellent catalyst in the phenylation reaction of Michael acceptors with phenylboronic acid so as to yield products such as (16). The nickel-catalysed reaction of phenylboronic acid with styryl epoxides has been shown to yield a-substituted alcohols such as (17). 

Brigas, A. F. and Johnstone, R. A. W. 2000. Hetero aromatic ethers of phenols in nickel-catalysed dipso-replacement reactions with magnesium, zinc and tin organometallic compounds./. Ghent. SPl. 11 1735-1739. 

The conversion of (298) into (300) upon gas-phase thermolysis occurs by a Cope rearrangement and not by a [1,3] carbon shift or a bisallyl radical mechanism. Thus, similar treatment of (299) affords only (301). Rearrangement of 3-oxobicyclo-[3,2,l]oct-6-ene to 3-oxobicyclo[3,3,0]oct-6-ene occurs only at much higher temperature and presumably by way of a non-concerted mechanism. The nickel-catalysed reaction of norbornene with butadiene affords the 1 2 cxo-adduct (302) which upon thermolysis is converted into the valence isomer (303). Concerted and non-concerted Claisen-type rearrangements have been observed in the A, -phosphorin series. Tricyclo[7,3,0,0 ]dodeca-2,5,7,10-tetraene (304), which is available in six steps starting from bicyclo[3,3,0]octa-3,7-dien-2,6-dione, appears to be an essentially static structure (as assessed by n.m.r. spectroscopy) up to 141 The slow... 

Enamides and enecarbamates are considered as versatile synthetic building blocks in organic synthesis, but they have been rarely used as nucleophiles, presumably due to their lower reactivity compared with enamines and enols. In 2004, Kobayashi et al demonstrated the utility of enecarbamates as nucleophiles for C-C bond formation in asymmetric copper-catalysed reactions of aldehydes and aldimines. Later in 2005, these authors reported the enantioselective nickel-catalysed reactions of a simple diketone, such... 

This chapter collects miscellaneous enantioselective nickel-catalysed reactions that could not be included in other chapters, such as cyclisation reactions, amination reactions, ring-opening reactions, Friedel-Crafts reactions, allylation reactions of aldehydes, and other reactions. It well demonstrates the remarkably diverse chemical reactivity exhibited by chiral nickel catalysts. 

---