Transfer hydrogenation ammonium formate hydrogen donor

Preparation from l-(4-benzyloxy-3-methoxyphenyl)-2-phenylethanone (m.p. 136-138°) by catalytic hydrogen transfer using ammonium formate as hydrogen donor and 10% Pd/C catalysis in refluxing methanol for 30 min (94%) [5193]. 

In addition to standard catalytic hydrogenolysis, methods for transfer hydrogenolysis using hydrogen donors such as ammonium formate or formic acid with Pd-C catalyst are available.216 The Cbz group also can be removed by a combination of a Lewis acid and a nucleophile for example, boron trifluoride in conjunction with dimethyl sulfide or ethyl sulfide.217... 

The rapid microwave-assisted deprotection of N-benzyl carbamate (Cbz) and AT-benzyl (Bn) derivatives in solution as well as on solid support was reported by Daga et al.26 Within this report, amino groups protected as benzyl carbamates or with simple benzyl groups could be deprotected in a few minutes by microwave-assisted catalytic transfer hydrogenation with palladium charcoal in isopropanol, employing ammonium formate as the hydrogen donor (Scheme 7.6). Both MeO-PEG and PS Wang-resin were used as soluble and solid supports, respectively, in these reactions. 

Their common feature is that the transfer of charge characteristic of intermediate salt or complex formation between donor and acceptor molecules facilitates simultaneously the release of positive and negative groups from adjacent atoms. In ammonium hexachlorophosphate, for example, the formation of the salt reduces electrostatic interaction, making easier the removal of the hydrogen atoms as protons. A chloride ion would be easily detached from a hexachlorophosphate ion. 

Sodium or ammonium formates are also suitable as hydride donors for the hydrogenation of a, 0-unsaturated and aromatic aldehydes with water-soluble Ru complexes [88, 93], With [RuCl2(TPPMS)2], both the catalyst and the formate are in the aqueous phase the phase-transfer problem associated with catalysts not soluble in water and aqueous formate solutions does not arise [93, 94]. These systems olfer interesting theoretical aspects [87, 95, 186]. 

The reductive animation of 3-oxo-l,2.3.4-tetrahydrocarbazole with (S)-phenylethylamine and sodium borohydride leads to (37 )-3-[(l.S )-phenylethylamino]-l,2,3,4-tetrahydrocarbazole in 39.7% yield. The cleavage of the phenylethyl group is accomplished by a transfer hydrogenation, with ammonium formate as a hydrogen donor and palladium on charcoal as a catalyst, to give the enantiomerically pure (3/ )-3-amino-l,2,3,4-tetrahydrocarbazole23. 

Benzyl ethers can be cleaved under hydrogen transfer conditions with many commonly used hydrogen donors such as ammonium formate,2-propanol,and cyclohexene. ... 

---