Microwave mediated reduction of heterocycle and fluorine containing nitroaromatics with Mo(CO)6 and DBU

Heterocycle containing nitroaromatics were reduced by Mo(CO)₆ and DBU in EtOH under microwave irradiation within 15 min. Under the same conditions, 4-fluoronitrobenzene was reduced to 4-fluoroaniline, whereas 2-chloro-1-fluoro-4-nitrobenzene afforded a mixture of 3-chloro-4-fluoroaniline and 3-chloro-4-ethoxyaniline. The extent of the competing S_NAr/reduction process could be influenced by the nature of the solvent, with t-BuOH the inert solvent of choice. The latter was used as solvent for S_NAr/reductions of 2-chloro-1-fluoro-4-nitrobenzene with S-nucleophiles to yield 3-chloro-4-mercaptoanilines.