Halides, aryl, arylation from amines, replacement

An excited aryl halide may also transfer charge to oxygen and thereby become activated towards attack by nucleophiles. The photoamination of 1-amino-2,4-dibromoan-thraquinone by rc-butylamine, in which the 4-Br atom is replaced, is supposed to proceed via direct interaction between the triplet state and the amine when the reaction is performed under nitrogen. In air atmosphere, however, it proceeds via both the T7, and SY states. From the singlet excited state and oxygen, an exciplex or collisional complex [AQ ()/ ] is formed which undergoes the animation639. 

Leeuwen and coworkers studied the kinetics for the amination of aryl triflates and bromides using different Xantphos catalyst systems. " For triflate amination, they found the rate to be first order in amine and ferf-butoxide, but zero order in aryl triflate. From this, they concluded that a mechanism similar to the upper pathway in Scheme 7 was operating, with the deprotonation of coordinated amine being the ratedetermining step. For aryl bromides, however, the rate was dependent on the concentration of iert-butoxide, but not amine or aryl bromide. Thus, under these conchtions, the lower pathway-with the replacement of halide by tert-butoxide as the rate-limiting step - was postulated to be the operating mechanism. 

Chlorobenzene is employed in the synthesis of certain amino-containing vat dye intermediates. When reacted with phthalic anhydride, the product is 2-chloroanthraquinone, which, with ammonia, is converted readily into 2-aminoanthraquinone (61). Other routes include replacement of halogen by amino groups, with ammonia or ammonium salts of urea, and alkyl- and aryl amines to afford secondary amines. Modification of the amino group by alkylation, with dimethyl sulfate, alkyl halides or esters of toluenesul-fonic acids, is of synthetic value. Arylation of the amino groups is of importance only in the reaction between aminoanthraquinones and nitro- or chloroanthraquinones to yield dianthraquinonylamines, or anthrimides48. For example, the reaction between 62 and 63 yields 64, which can then be converted into carbazole 65, Cl Vat Brown R (Scheme 14). Amination of haloanthraquinones such as l-amino-4-bromoanthraquinone-2-sulfonic acid (bromamine acid) (66), prepared from 1-aminoanthraquinone, is of industrial use. 

Several papers deal with the products of (formally) "double carbonylation" reactions. The carbonylation product of styrene oxide in the presence of a Co2(C0)g/MeI catalyst under phase-transfer conditions contains two CO derived carbons (eqn.17). Two groups report the synthesis of a-keto esters from aryl iodides, CO, alcohols and tertiary amines the selectivity depends on Replacement of alcohol by water leads to a-keto acids. a-Keto-amides are prepared similarly from secondary amines. In this case the mechanism has been studied in detail oxidative addition of the aryl halide is the rate-determining step (Scheme 5). °... 

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