Replacement of aromatic

Reductive methylation of the tetrahydropyranyl ether of 17o -acetoxy-3/3-hy-droxypregn-5-en-20-one, 56 Replacement of aromatic amino groups by fluorine, 450... 

Replacement, of aromatic chlorine atoms, by amino groups using ammonia, 40, 97... 

Replacement of aromatic COOH by halogen Replacement of aromatic S02Br by halogen Migration of halogen... 

Replacement of aromatic halogens with OAr groups (example 4, Table IX) seems to follow the same patterns already mentioned for other substitution reactions. 

Also the bio-isosteric potential of the pyridazine system hitherto remained largely unexplored, despite the fact that several examples discussed in this review indicate that the replacement of aromatic moieties in bio-ac-tive compounds by the highly polar pyridazine nucleus may well improve the pharmacodynamic and/or the pharmacokinetic profile of a drug molecule. 

Hypophosphorous acW H3PO2 (M.W. 66.00), usually available as its 50% aqueous solution (density 1.274), is a specific reagent for replacement of aromatic diazonium groups by hydrogen under very mild conditions (at 0-25°) and in fair to good yields [288, 289] Procedure 46, p. 217). 

Replacement of Aromatic Primary Amino Groups by Hydrogen [594 ... 

Sodium fluoride does not effect any replacement of aromatic chlorine atoms with fluorine, unless they are activated by substitution of electron-withdrawing groups in the ring. Several examples are reported for heterocyclic compounds. 

This reaction has general utility for replacement of aromatic amino groups by hydroxyl groups. In contrast to the behavior of alkylamines, no rearrangements occur. 

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