Organomagnesium species

In a nucleophilic solvent, the organomagnesium species not only exists as RMgX, but is rather described by the Schlenk equilibrium ... 

Heterocyclic derivatives of the cyclopentadienyl ligand have been incorporated in organomagnesium species. The reaction of bis(cyclopentadienyl)-l-zircona-2,3,4,5-tetraethylcyclopenta-2,4-diene with ECI3 (E=P, As, Sb) yields... 

The question of the solution structure of allyhnagnesium compounds is an intriguing one and such compounds have been studied in more detail by NMR than any other organomagnesium species. H and NMR data for selected allylmagnesium compounds are given in Tables 4 and 5, respectively. 

Formation, chemistry and structure of organomagnesium species in solvent-free environments... 

Finally, two studies have reported on the reactions of carbocations with Mg atoms using mass spectrometry The types of products formed depend on the nature of the carbocation. The labeled methanium ion, CH4D+, reacts via proton transfer (equation 11), deuteron transfer (equation 12) and charge transfer (equation 13). The ethyl cation reacts via charge transfer (equation 14) while the tert-butyl cation reacts via proton transfer (equation 15). In all cases there was no evidence for formation of an organomagnesium species. 

Low reactive aryl chlorides are converted to the respective organomagnesium species in excellent yields through transition metal catalysis using 2 mol% FeCU (4-6, equation 3). Alternatively, a safe and reproducible method for activation of aryl chlorides or bromides 7 uses microwave irradiation (equation 4). In a synthesis of a novel HIV-1 protease inhibitor, microwave irradiation was essential to generate the starting arylmagnesium halide as well as to promote the subsequent Kumada coupling reaction. ... 

The enantioselective addition of organomagnesium compounds to ketones can be most conveniently performed by using a chiral auxiliary in the substrate molecule. Primary aUsyhnagnesium reagents react with aryl and heteroaryl ketones in the presence of magnesium TADDOLate at — 100°C, yielding products with up to 98% ee (equation 143). Chiral a-ketoacetals 214, prepared in two steps from a-substituted cinnamic aldehydes, add organomagnesium species with up to 98% diastereoselectivity (equation 144). 

Chromium salts can catalyze the carbomagnesiation reactions of 1,6-enynes with cy-clization (Scheme 12) . This reaction is probably initiated by carbometalation of the alkyne unit. The resultant organomagnesium species 16 undergoes further functionalization upon treatment with various electrophiles (Scheme 12) . ... 

Subseqnent reactions of thus-generated organomagnesium species are also possi-blei° i°7. For example, a-silylorganomagnesium compound 91 is allowed to react with... 

Schlenk equilibrium [13] the simpler diorganomagnesium compounds are often easier to study [14,78,79] because of the absence of complications from additional halide ligands. As the organolithium compounds, organomagnesium species often react rapidly at ambient temperatures with substrates so that the charge transfer intermediates are not observed or reported. 

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