Electron-transfer reactions. Oxidation of Grignard reagents in the presence of an aminoxyl as a radical-trapping agent

1991 ◽  
Vol 56 (15) ◽  
pp. 4733-4737 ◽  
Author(s):  
Patricia Carloni ◽  
Lucedio Greci ◽  
Pierluigi Stipa ◽  
Lennart Eberson
Keyword(s):  
Electron Transfer ◽  
Transfer Reactions ◽  
Grignard Reagents ◽  
Electron Transfer Reactions ◽  
Radical Trapping ◽  
Trapping Agent

Grignard reagents in ionic solvents: electron transfer reactions and evidence for facile Br–Mg exchange

2007 ◽  
pp. 2066-2068 ◽  
Author(s):  
Taramatee Ramnial ◽  
Stephanie A. Taylor ◽  
Jason A. C. Clyburne ◽  
Charles J. Walsby
Keyword(s):  
Electron Transfer ◽  
Transfer Reactions ◽  
Grignard Reagents ◽  
Electron Transfer Reactions

Reaction of 5-nitro-octaethylporphyrins with nucleophiles

2002 ◽  
Vol 06 (11) ◽  
pp. 685-694 ◽  
Author(s):  
Maxwell J. Crossley ◽  
Lionel G. King ◽  
Simon M. Pyke ◽  
Charles W. Tansey
Keyword(s):  
Electron Transfer ◽  
Nitro Group ◽  
Transfer Reactions ◽  
Nucleophilic Attack ◽  
Grignard Reagents ◽  
Free Base ◽  
Lower Efficiency ◽  
Electron Transfer Reactions ◽  
Ipso Substitution ◽  
Two Factors

An investigation of the reactions of metallo-5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrins with Grignard reagents, benzyl oxide, phenoxide and benzenethiolate nucleophiles shows that, except for benzenethiolate reactions, they are less efficient than related reactions of metallo-2-nitro-5,10,15,20-tetraarylporphyrins. Treatment of free-base and nickel(II) 5-nitro-octaethylporphyrin with the “soft” nucleophile benzenethiolate in DMF affords the corresponding 5-phenylthioporphyrins in 61 and 72% yield, respectively, by ipso-substitution of the nitro group. In contrast, with methylmagnesium iodide and benzyl oxide, “hard” nucleophiles, attack is at the diagonally opposite 15-position of the ring to give 15-substituted 5-nitroporphyrin while with phenoxide and more substituted Grignard reagents, electron-transfer reactions lead to denitration to (metallo)-octaethylporphyrin or reduction to the corresponding 5-aminoporphyrin. The lower efficiency of the latter reactions, compared to those on 2-nitro-tetraarylporphyrin analogues, is a consequence of two factors, higher energies being required for initial nucleophilic attack as macrocyclic aromaticity is lost in intermediates and the susceptibility of the resultant “non-aromatic” intermediates to further attack.

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