Thearyl amine moiety is frequently found as a key structural element in compounds thatare of biological, pharmaceutical and materials interest. C-N bond-formingprocesses are already utilized in the medicinal chemistry and processdevelopment groups of pharmaceutical companies and in academic laboratories.1–3Metal promoted transformation of aryl halides to various heteroatomicfunctional group is an ever-expanding class of reaction in synthetic chemistry.These reactions provide new route to many compounds of medicinal and industrialimportance.
4 Their widespread importance has led to the developmentof many synthetic methods for the formation of arylnitrogen bonds.1,5Amongst them, the classical copper-mediated Ullmann coupling and palladium-catalyzedaryl coupling are the more commonly used methods.6–13 Classicalcopper-mediated aryl coupling reactions have few drawbacks. Most copper (I)salts are insoluble in organic solvents, and hence, the reactions are oftenheterogeneous and require high reaction temperatures (200 ºC) and large amountsof copper reagents than stoichiometric amounts.14 The reaction isalso very sensitive to the substitution on the aryl halide. Palladium-catalyzedaryl amine also has some problem of extreme reaction temperatures and high costof palladium.
15 An important alternative Copper-catalyzed methods hasbeen reported recently where triarylbismuth16 aryl lead triacetates17aryl boronic acids18 and hypervalent aryl siloxanes19 areused as arylating agents instead of aryl halides, the utility of these variantsis limited since the preparation of highly functionalized substrates usuallyrequires multistep sequences and suffers from high cost, toxicity and limitedscope of the process.Arecent report also described the solid phase preparation of aryl amines viadisplacement of aromatic bromides by various amines in reflux condition.20,21The synthesis of aryl amines usually need metals for arylation, requireshigh temperature22 or functionalizations of any functional group intomore active derivatives (eg., halides, triflates, tosylates, carbamatederivatives)23 followed by cross coupling reactions.