Selective synthesis of 2,6-naphthalenedicarboxylic acid by use of cyclodextrin as catalyst

The selective synthesis of 2,6-naphthalenedicarboxylic acid from 2-naphthal enecarboxylic acid with carbon tetrachloride, copper powder, and aqueous al kali was achieved by using of beta-cyclodextrin (beta-CyD) as a catalyst at 60 degrees C under nitrogen, producing 2,6-naphthalenedicarboxylic acid in 67 mol% yield with 84% selectivity, The one-pot preparation of 2,6-naphtha lenedicarboxylic acid from naphthalene was attained at 84 degrees C by usin g of beta-CyD, producing 2,6-naphthalenedicarboxylic acid in 65 mol% yield with 79% selectivity. When alpha-CyD or gamma-CyD was used instead of beta- CyD on the carboxylation of 2-naphthalenecarboxylic acid and naphthalene, r espectively, the reaction hardly proceeded. The conformation of beta-CyD-2- naphthalenecarboxylate inclusion complex in aqueous alkaline solution was d etermined by the nuclear magnetic resonance spectroscopy using H-1 homonucl ear Overhauser enhancement on the rotating frame. The 2-naphthalenecarboxyl ate anion was axially included in the cavity of beta-CyD with an orientatio n which directed the 5-, 6-, and 7-positions of 2-naphthalene carboxylate a nion to the secondary hydroxyl side of beta-CyD, It was concluded that the high selectivity of the carboxylation of 2-naphthalenecarboxylic acid was a scribed to the conformation of the beta-CyD-2-naphthalenecarboxylate inclus ion complex. The selective carboxylation of naphthalene was attributed to t he formations of the beta-CyD-naphthalene and beta-CyD-2-naphthalenecarboxy late inclusion complexes. (C) 1999 Elsevier Science B.V. All rights reserve d.