Hydrogenation ammonium formate hydrogen donor

Alcohols or phenols protected by benzyloxycarbonyl groups are very smoothly reduced over Pd/C using phosphinic acid or sodium phosphinate as hydrogen donor. Effective cleavage of an allylic r-amine has been demonstrated (equation 16) utilizing ammonium formate as donor. The lack of tegiospeci-ficity could possibly be overcome by selective use of catalysts. For example, double bond migration can be influenced by Pd/Hg or Pd/Pb catalysts. ... 

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... 

Formic acid is a widely used hydrogen donor.240 Flowever, since the active species in formic acid is the formate anion, it has been demonstrated that formate salts are superior to formic acid. Ammonium formate is used frequently as a hydrogen donor.241-243... 

Bose and coworkers [10] have described hydrogenation using ammonium formate as hydrogen donor and Pd/C as catalyst for selective transformations (Tab. 8.1) of /7-lactams 10, as shown in Scheme 8.6. 

The product is an equilibrium mixture and an excess of 2-propanol must be used to obtain high yields. Ammonium formate or formic acid have also been used as the hydrogen donor and now the reaction to the alcohol is complete, because the thermodynamics are more favourable and because C02 leaves the reaction medium. 

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. 

Cinnamic acid and its derivatives were reduced in high yields under mild conditions using ammonium formate as hydrogen donor, in the presence of palladium(II) as catalyst in ionic liquids.294... 

The method using ammonium formate as a hydrogen donor has been reported to accelerate the reaction, but the selectivity of the reduction excludes nitro, halo or alkenic groups, which are reduced faster than the carbonyl group. ... 

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. 

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