Grignard reagents, alkyl

The coupling of alkyl Grignard reagents with alkyl iodides to afford alkanes by use of dppf as a ligand has been reported[449], but re-examination of the reaction has shown that only reduction takes place, and no coupling was observed[450]. 

Reaction of pyridazine 1-oxide with phenylmagnesium bromide gives 1,4-diphenyl-butadiene as the main product and l-phenylbut-l-en-3-yne and 3,6-diphenylpyridazine as by-products, while alkyl Grignard reagents lead to the corresponding 1,3-dienes exclusively (79JCS(P1)2136>. 

In contrast to these ring-opening reactions, it was observed by Horner and Schwahn that 4-arylidene-(isopropylidene and cyclo-hexylidene)-oxazolones react with alkyl Grignard reagents by conjugate addition to give saturated azlactones 29a as the only products [Eq. (18)]. 

The reaction of tert-alkyl Grignard reagents with carboxylic acid chlorides in the presence of a copper catalyst provides ieri-alkyl ketones in substantially lower yields than those reported here.4,14 The simplicity and mildness of experimental conditions and isolation procedure, the diversity of substrate structural type, and the functional group selectivity of these mixed organocuprate reagents render them very useful for conversion of carboxylic acid chlorides to the corresponding secondary and tertiary alkyl ketones.15... 

Although the formation of tetraalkylferrates, for example, in the first step of a cross-coupling reaction starting from Fe(-i-3)-salts and alkyl Grignard reagents, seems possible, until now there is no analytical or spectroscopic proof for such a species. In fact, it was shown that Fe(-i-3) is reduced by MeLi or MeMgBr to Fe(-i-2) under release of ethane [5, 6]. 

Alkyl lithium and alkyl Grignard reagents react with aromatic nitro compounds in a similar way to give alkylated products (Eq. 9.23).37... 

Metal alkyls can be prepared in a simple manner from the main group halides (X = Cl, Br, I) and the appropriate alkyl Grignard reagent (RMgl) or the alkyllithium salt (RLi), as shown for the cadmium alkyls (Equation (2)).13 The elimination of impurities from the precursor source is of great importance, as any remaining impurities are invariably carried over into the growing semiconductor layers. Incorporation of impurities, even at levels as low as 1015 free carriers per cubic centimeter (one part in ca. 107), can drastically affect the electronic properties of the... 

Organometallic compounds vary widely in their properties and reactivity, just as do the elements from which they are produced. These compounds may be lithium alkyls, Grignard reagents, or organotin compounds. Accordingly, there is no universal method for preparing the compounds, but we will present here some of the types of reactions that have been widely employed. 

Scheme 15 Reaction of conjugated dienes with alkyl Grignard reagents and CI2TiCp2.

As already mentioned, unsubstituted PT is an insoluble and infusible material. Once the polymer is prepared, it is difficult (if not impossible) to further process it as a material for electronic applications. The solubility can be greatly enhanced by the introduction of side chains at position 3 (or at both, 3 and 4). The most widely studied side chains are n-alkyl substituents that can be easily introduced into the thiophene core by reaction of 3-bromothio-phene with alkyl-Grignard reagents [464]. 

Examples Aluminum alkyl Grignard reagent Finely divided metals Iron sulfide Examples Noncombustible materials Flammables or combustibles needing an ignition source to start burning... 

Figure 3.47. Scope of Ni/49-catalyzed asymmetric cross-coupling of vinyl bromide with secondary alkyl Grignard reagents.

When cyclohexanone oxime 6e was used as amination reagent, primary amines were obtained from phenylmagnesium bromide. Reaction of 6e with alkyl Grignard reagents gave aziridines, whereas reaction with phenyllithium gave aziridine and the addition product of phenyllithium to the imine (Scheme 57) 24. 

The isoselective polymerization of acetaldehyde has been achieved using initiators such as zinc and aluminum alkyls, Grignard reagents, and lithium alkoxides [Kubisa et al., 1980 Pasquon et al., 1989 Pregaglia and Binaghi, 1967 Tani, 1973 Vogl, 2000], The isoselectivity is high in some systems with isotactic indices of 80-90%. Cationic initiators such as BF3... 

Further investigations are needed to establish, whether this approach is really useful to obtain chiral allylsilanes 2, which are synthetically quite interesting intermediates. They are available otherwise only by asymmetric cross-coupling of silyl alkyl Grignard reagents with bromoethylenes in the presence of a chiral ferrocenylphosphine-palladium catalyst54. 

Many transition metal alkyls react with carbon monoxide to give acyl compounds. In all these cases the acyl derivatives can be detected at least by infrared methods and in most cases isolated. Molybdenum, manganese, rhenium, iron, cobalt, rhodium, nickel, palladium, and platinum alkyls, Grignard reagents, and boranes, all react with carbon monoxide, and one can explain the products from these on the basis of carbon monoxide inserting into the metal alkyl. 

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