Straightforward heterogeneous palladium catalyzed synthesis of aryl ethers and aryl amines via a solvent free aerobic and non-aerobic dehydrogenative arylation

Abstract

Aryl ethers have been prepared from cyclohexanone derivatives and various alcohols in the presence of a catalytic amount of palladium on charcoal. The formation of an enol ether followed by an aerobic or non-aerobic dehydrogenation reaction, seem to be the key steps of this transformation. In addition, this new method was also adapted for the synthesis of arylamines.Scheme 1 Envisaged methodology for the synthesis of aryl ethers by a heterogeneous catalyzed solvent free dehydrogenative arylation using cyclohexanone derivatives, alcohols and biosourced polyols. † Electronic supplementary information (ESI) available. See

Aerobic Dehydrogenation of Cyclohexanone to Cyclohexenone Catalyzed by Pd(DMSO)2(TFA)2: Evidence for Ligand-Controlled Chemoselectivity

“…22,23 And, Imahori et al recently reported a Pd-catalyzed C–H arylation-aromatization of cyclohexenone that furnishes 4-arylphenol derivatives, again consistent with Pd-mediated cleavage of the allylic C–H bond. 12b …”

“…A number of related transformations, including reactions for the synthesis of aryl ethers and anilines from cyclohexanones and cyclohexenones, have been reported by other groups over the past year. 12 …”

Palladium-Catalyzed Aerobic Dehydrogenation of Cyclic Hydrocarbons for the Synthesis of Substituted Aromatics and Other Unsaturated Products

“…16 Both cyclohexanones and cyclohexenones were effective substrates, as well as tetralones (Scheme 10). …”

Catalytic Aerobic Dehydrogenation of Nitrogen Heterocycles Using Heterogeneous Cobalt Oxide Supported on Nitrogen-Doped Carbon

“…2 In many cases, these methods enable synthesis of aromatic compounds with substitution patterns and/or functional groups that are difficult to access via traditional aromatic functionalization reactions. This strategy has been employed by us and others in Pd-catalyzed methods for the conversion of cyclohexanone and cyclohexenone derivatives into substituted phenols, 3 aryl ethers 4 or anilines 5 and for the conversion of cyclohexene derivatives into substituted arenes. 6 More recently, we began exploring methods for aerobic dehydrogenation of partially saturated N -heterocycles to heteroarenes.…”