Acenaphtene-1-carboxylic acid methyl ester by palladium-catalyzed chemoselective hydroesterification of acenaphthylene

The hydroesterification of acenaphthylene with carbon monoxide and methanol, catalyzed by PdII/PR3 systems (PR3 = PPh3, P(o-MeC6H4)3, P(p-MeC6H4)3, P(p-FC6H4)3, P(iBu)3, PEt3, PCy3, P(OEt)Ph2, P(OPh)3, P(O-o-MeC6H4)3, P(O-o-tBuPh)3, dppm, dppe, dppp, dppb, 1,1′-bis(diphenylphosphino)ferrocene (dppf), rac-BINAP) has been studied, the reaction yields a mixture of acenaphthene-1-carboxylic acid methyl ester 1, 1-methoxyacenaphthene 2 and polyacenaphthylene 3. For Pd/monophosphine/p-TsOH precursors, only ligands with intermediate electronic and steric properties formed active catalytic systems with satisfactory chemoselectivities. These systems are highly influenced by the reaction conditions, as the methanol concentration and the Pd/p-TsOH ratio, yielding conversions up to 85% with a chemoselectivity in ester 1 of 93%. When diphosphines were used as auxiliary ligands, less efficient catalytic systems were produced and their characteristics can be attributed to the electronic properties of the ligands, yielding conversions up to 60% and chemoselectivities in ester 1 of 85%. © 2002 Elsevier Science B.V. All rights reserved.