Ipso nucleophilic aromatic substitution

Tab. 1. Ipso nucleophilic aromatic substitution of arenetricarbonylchromium complexes C-O, C-S and C-Se bond formation.

It has been shown recently by Park et aL that also Grignard reagents can be used to cleave sulfonate esters [304]. For this traceless biphenyl-forming reaction Ni(0)-catalysts (NiCl2dppe) have to be added to permit ipso nucleophilic aromatic substitution of the alkyloxysulfonyl groups. 

This chapter covers reactions in which coordination of a transition metal to the ir-system of an arene ring activates the ring toward addition of nucleophiles, to give V-cyclohexadienyl-metal complexes (1 Scheme 1). If an electronegative atom is present in the ipso position, elimination of that atom (X in 1) leads to nucleophilic aromatic substitution (path a). Reaction of the intermediate with an electrophile (E+) can give disubstituted 1,3-cyclohexadiene derivatives (path b). If a hydrogen occupies the ipso posi-... 

The chemistry involved in nucleophilic aromatic substitution is well reflected in the reactions of a variety of nucleophiles with methyl penta-fluorophenyl ether (Ingemann et al 1982a). For most of the nucleophiles such as alkoxide, thiolate, enolate and (un)substituted allyl anions, the dominant reaction channel is the attack upon the fluoro-substituted carbon atoms, as is the case for OH-. The latter ion reacts approximately 75% by attack upon the fluoro-substituted carbon atoms and the remaining 25% by Sn2 (20%) and ipso (5%) substitution as summarized in (41). In the attack upon the fluorinated carbon atoms, the interesting observation is made that a F- ion is displaced via an anionic o-complex to form a F- ion/molecule complex, which is not observed to dissociate into F- as a free ionic product. 

Ipso, Cine, Tele Nucleophilic Aromatic Substitutions... 

A radical cyclization approach to spiro-oxindoles was revealed <05OL151>. Treatment of p-trityloxybenzamide 125 with triethylborane and tris(trimethylsilyl)silane gave cyclohexadienone 126 via an ipso cyclization. The nucleophilic aromatic substitution of aryl fluorides was utilized in an asymmetric approach to spiro-pyrrolidone oxindoles <05JA3670>. 

Nucleophilic aromatic substitution Ipso subsiiiuiion, giving phenols, henzen-amines (anilenes), or alkoxybenzcnes. 

A detailed study of the nucleophilic aromatic substitution of hydrogen has been initiated at the Urals State Technical University (Russia) in the 1970s. In the first review on this topic, it was suggested to use the symbol Sjj in order to distinguish these reactions from the classical nucleophilic ipso-substitution Ar [8]. Later, a number of special reviews [9-38] and also the book Nucleophilic Aromatic Substitution of Hydrogen [39], which accumulated a considerable body of data on conditions, kinetics, structure of intermediates, electrochemical and mathematic modeling, as well as plausible mechanisms and the general concept of the 5 -reactions, have also been published. 

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