High-pressure synthesis aryl complexes

The arylation of ammonia remains one of the most attractive entry points for the synthesis of arylamines. Ammonia is inexpensive and readily available however, it is a gas at room temperature under atmospheric pressure. This significantly increases the operational complexity of its use and requires high-pressure reaction vessels. To address these issues, a range of ammonia alternatives have been used in the synthesis of arylamines. While some were more successful than others, many tended to suffer from an additional complication due to a competing diarylation reaction that led to the formation of diarylamines. A practical solution to the selective synthesis of aniline derivatives was reported by Hartwig... 

The direct reductive amination (DRA) is a useful method for the synthesis of amino derivatives from carbonyl compounds, amines, and H2. Precious-metal (Ru [130-132], Rh [133-137], Ir [138-142], Pd [143]) catalyzed reactions are well known to date. The first Fe-catalyzed DRA reaction was reported by Bhanage and coworkers in 2008 (Scheme 42) [144]. Although the reaction conditions are not mild (high temperature, moderate H2 pressure), the hydrogenation of imines and/or enam-ines, which are generated by reaction of organic carbonyl compounds with amines, produces various substituted aryl and/or alkyl amines. A dihydrogen or dihydride iron complex was proposed as a reactive intermediate within the catalytic cycle. 

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