Ionic hydrogenation 1-naphthol

In a series of papers, Koltunov, Repinskaya, and co-workers have reported the ionic hydrogenation of isomeric naphthols and dihydroxynaphthalenes with alkanes in the presence of aluminum halides. 1-Naphthol and substituted derivatives undergo regioselective reduction under mild conditions in excess alkane and aluminum halides with the involvement of various reactive intermediates to yield a-tetralone derivatives874 [Eq. (5.322)]. Byproducts are 3-, 6-, and 7-alkyl-substituted derivatives. Mechanistic studies875 with cyclohexane-di2 showed that deuterium incorporation takes place exclusively at C(4), indicating the involvement of super-electrophilic dication 263.2-Naphthol is much less reactive and complete conversion cannot be achieved.876... 

Carboxonium-carbenium dications have also been proposed in the reactions of aryl ethers, phenols, and naphthols, with superacids. When 2-naphthol is reacted with an excess of AICI3 (3 equivalents) and cyclohexane, the product of ionic hydrogenation is observed in 59% yield (eq 15).24 This conversion is thought to occur by double protonation of the 2-naphthol ring to give the dication 48, which is capable of abstracting hydride from cyclohexane. Similar intermediates are formed by the reactions of HF-SbFs with naphthyl ethers (eq 16).25... 

H. J. Neusser and K. Siglow, High-resolution ultraviolet spectroscopy of neutral and ionic clusters hydrogen bonding and the external heavy atom effect, Chem. Rev. 100,3921-3942 (2000). Y. Matsumoto, T. Ebata, and N. Mikami, Structures and vibrations of 2-naphthol-(NH3) (n = 1-3) hydrogen-bonded clusters investigated by IR-UV double-resonance spectroscopy, J. Mol. Struct. 552, 257-271 (2000). 

Ionic liquids (room-temperature molten salts) with chiral cations were efficiently used as reaction media to prepare homochiral MOFs [33], But the use of homochiral ligands as precursors in the synthesis is even more efficient For instance, Lin et al. [34] prepared MOFs with BINOL (l,l -bi-2,2 -naphthol) and BINAP (2,2 -his(diphenylphosphino)-1,1 -binaphthyl) as chiral linkers. Unfortunately, attempts to use such chiral catalysts in asymmetric catalysis showed some but not high enantiomeric excess in the studied reactions, perhaps the flexibility of the ligands in the MOF framework is not sufficient to induce the chirality effect in the reactions. The most illustrative example was presented hy Lin [35] the reaction of asymmetric hydrogenation of aromatic ketones demonstrated a 99.2% ee for Ru-BINAP/MOF systems. 

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