Formic acid and formates
Deprotonated formic acid splits into hydride and CO2, wherefore it works as a reducing agent.
> Formic acid as an oxidizing agent.
In a biphasic reaction media for the asymmetric biocatalytic reduction of ketones with in situ cofactor regeneration, both enzymes (ADH and FDH) remain stable. Reductions with poorly water-soluble ketones were carried out at substrate concentrations of > 10 mM, and alcohols were formed with good conversions in high enantioselectivity.
H. Groeger, W. Hummel, S. Buchholz, K. Drauz, T. V. Nguyen, C. Rollmann, H. Huesken, K. Abokitse, Org. Lett., 2003, 5, 173-176.
By careful selection of appropriate enzymes (alcohol dehydrogenases [ADH] and cofactor recycling enzymes), cofactor recycling of NADH can be performed in the presence of NADP+ recycling to achieve overall (R)- or (S)-selective deracemisations of sec-alcohols or stereoinversion representing a possible concept for a “green” equivalent to the chemical-intensive Mitsunobu inversion.
C. V. Voss, C. C. Gruber, K. Faber, T. Knaus, P. Macheroux, W. Kroutil, J. Am. Chem. Soc., 2008, 130, 13969-13972.
An on-water Ir(III)-diamine catalysis represents an efficient, simple and environmentally friendly catalytic system for the transfer hydrogenation of aldehydes. The catalyst tolerates various synthetically useful groups including nitro groups, halogens, ketones, esters and olefins.
X. Wu, J. Liu, X. Li, A. Zanotti-Gerosa, F. Hancock, D. Vinci, J. Ruan, J. Xiao, Angew. Chem. Int. Ed., 2006, 45, 6717-6722.
Asymmetric transfer hydrogenation of various simple aromatic ketones by the Ru-TsDPEN catalyst was shown to be feasible in aqueous HCOONa without calling for any catalyst modification, furnishing ee's of up to 95% and significantly faster rates than in the HCOOH-NEt3 azeotrope.
X. Wu, X. Li, W. Hems, F. King, J. Xiao, Org. Biomol. Chem., 2004, 2, 1818-1821.
The neutral gold(I) complex [(IPr)AuCl] is a highly effective catalyst for the regioselective hydration of terminal alkynes, including aromatic alkynes and aliphatic alkynes providing methyl ketones in high yields. Furthermore, optically active alcohols could be obtained in high yields with very good enatioselectivities via one-pot sequential hydration/asymmetric transfer hydrogenation using Cp*RhCl[(R,R)-TsDPEN] as additional catalyst.
F. Li, N. Wang, L. Lu, G. Zhu, J. Org. Chem., 2015, 80, 3538-3546.
An iridium-catalyzed, chemoselective, asymmetric transfer hydrogenation of α-substituted acetophenones using formic acid as reductant can be performed in water and open to air.
O. Soltani, M. A. Ariger, H. Vázquez-Villa, E. M. Carreira, Org. Lett., 2010, 12, 2893-2895.
In a one-pot synthesis of optically active β-hydroxy sulfones, intermediate β-keto sulfones obtained via a nucleophilic substitution reaction of α-bromoketones and sodium sulfinates were reduced through Ru-catalyzed asymmetric transfer hydrogenation using HCOONa as a hydrogen source. This mild transformation in an aqueous medium provides chiral β-hydroxy sulfones with high yields and excellent enantioselectivities.
D. Zhang, T. Cheng, Q. Zhao, J. Xu, G. Liu, Org. Lett., 2014, 16, 5764-5767.
A pH-independent asymmetric transfer hydrogenation of β-keto esters in water with formic acid/sodium formate can be conducted open to air and gives access to β-hydroxy esters in excellent yields and selectivities.
M. A. Ariger, E. M. Carreira, Org. Lett., 2012, 14, 4522-4524.
The use dynamic kinetic resolution combined with asymmetric transfer hydrogenation in water provides β-hydroxy-α-(tert-butoxycarbonyl)amino esters in good yields, diastereoselectivities, and enantioselectivities. A surfactant is employed to achieve good yields due to the hydrophobic nature of both the catalyst and substrate.
B. Seashore-Ludlow, F. Seint-Dizier, P. Somfai, Org. Lett., 2012, 14, 6334-6337.
A new diamine ligand for Ru-catalyzed asymmetric transfer hydrogenation (ATH) enabled a highly enantioselective reduction of 2-acylarylcarboxylates. Subsequent in situ lactonization under aqueous conditions provided efficient access to a various 3-substituted phthalides in enantiomerically pure form.
B. Zhang, M.-H. Xu, G.-Q. Lin, Org. Lett., 2009, 11, 4712-4715.
A well-defined iron-based catalyst system enables the reduction of nitroarenes to anilines using formic acid as reducing agent. A broad range of substrates including other reducible functional groups were converted to the corresponding anilines in good to excellent yields at mild conditions. Notably, the process constitutes a rare example of base-free transfer hydrogenations.
G. Wienhöfer, I. Sorribes, A. Boddien, F. Westerhaus, K. Junge, H. Junge, R. Llusar, M. Beller, J. Am. Chem. Soc., 2011, 133, 12875-12879.
In the presence of iodide ions, an efficient and selective rhodium-catalyzed transfer hydrogenation of nitroarenes with formic acid as the hydrogen source takes place to give amines or formanilides.
Y. Wei, J. Wu, D. Xue, C. Wang, Z. Liu, Z. Zhang, G. Chen, J. Xiao, Synlett, 2014, 25, 1295-1298.
Aryl azides undergo clean reduction by copper nanoparticles in water in the presence of ammonium formate. The surface hydrogen on copper nanoparticles is considered to be the active reducing species. Various functionalized aryl azides and aryl sulfonyl azides are reduced to the corresponding amines with excellent chemoselectivity in high yields.
S. Ahammed, A. Saha, B. C. Ranu, J. Org. Chem., 2011, 76, 7235-7239.
A transformation of aldehydes into terminal olefins through reduction of the corresponding enol triflates is effective with both linear and α-branched aldehydes.
S. K. Pandey, A. E. Greene, J.-F. Poisson, J. Org. Chem., 2007, 72, 7769-7770.
An unprecedented reduction of alkynes with formic acid can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the reaction conditions via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Brønsted acid and Pd(0) complex.
R. Shen, T. Chen, Y. Zhao, R. Qiu, Y. Zhou, S. Yin, X. Wang, M. Goto, L.-B. Han, J. Am. Chem. Soc., 2011, 133, 17037-17044.
The use of unsupported nanoporous gold (AuNPore) as a heterogeneous catalyst enables a facile, highly chemo- and stereoselective transfer semihydrogenation of alkynes to Z-olefins in the presence of formic acid as a hydrogen donor. Various alkynes were reduced to the corresponding alkenes in high chemical yields with good functional-group tolerance. The catalyst is robust enough to be reused without leaching.
Y. S. Wagh, N. Asao, J. Org. Chem., 2015, 80, 847-851.
Pd/P(t-Bu)3 is an efficient and mild catalyst for selective reduction of various alkenes under transfer-hydrogenation conditions leading to the corresponding saturated derivatives in good yields.
J. M. Brunel, Synlett, 2007, 330-332.
An air-stable half-sandwich ruthenium complex is a highly active catalyst for the anti-Markovnikov reductive hydration of alkynes, involving the decarboxylation of formic acid, hydration of the alkyne, and hydrogenation of the intermediate aldehyde. A wide array of terminal alkynes are efficiently processed to linear alcohols using as little as 2 mol % of catalyst at ambient temperature.
M. Zeng, L. Li, S. B. Herzon, J. Am. Chem. Soc., 2014, 136, 7058-7067.
Palladium-catalyzed reductive coupling reactions between N-tosylhydrazones and aryl halides provide a general route for the synthesis of triarylmethanes.
Y. Xia, F. Hu, Z. Liu, P. Qu, R. Ge, C. Ma, Y. Zhang, J. Wang, Org. Lett., 2013, 15, 1784-1787.
A mild catalytic asymmetric transfer hydrogenation of β,β-disubstituted nitroalkenes using formic acid as reductant in combination with an Ir catalyst is conducted in water at low pH and open to air to give products in good yield and selectivity.
O. Soltani, M. A. Ariger, E. M. Carreira, Org. Lett., 2009, 11, 4196-4198.
Various carbon-carbon double bonds in olefins and α,β-unsaturated ketones were effectively reduced to the corresponding alkanes and saturated ketones, using ammonium formate as a hydrogen transfer agent in the presence of Pd/C as catalyst in refluxing methanol.
Z. Paryzek, H. Koenig, B. Tabacka, Synthesis, 2003, 2023-2026.
A microwave-assisted, palladium-catalyzed catalytic transfer hydrogenation of different homo- or heteronuclear organic compounds using formate salts as a hydrogen source was performed in ([bmim][PF6]. Essentially pure products could be isolated in moderate to excellent yields by simple liquid-liquid extraction.
H. Berthold, T. Schotten, H. Hönig, Synthesis, 2002, 1607-1610.
Knoevenagel condensation followed by hydrogenation with triethylamine-formic acid in the presence of a ruthenium-amido complex allowed an α-alkylation of various nitriles with carbonyl compounds in good yields. The reaction tolerated various functional groups, including nitro and chloro groups, and a furan ring.
H. Sun, D. Ye, H. Jiang, K. Chen, H. Liu, Synthesis, 2010, 2577-2582.
Transfer hydrogenation utilizing palladium on carbon and formic acid provides a fast and simple removal of O-benzyl groups from carbohydrate derivatives. However, when formic acid is the hydrogen donor, a large amount of palladium has to be used.
T. Bieg, W. Szeja, Synthesis, 1985, 76-77.
Nanopalladium particles supported on a amphiphilic polystyrene-poly(ethylene glycol) resin catalyzed hydrogenation of olefins and hydrodechlorination of chloroarenes under aqueous conditions.
R. Nakao, H. Rhee, Y. Uozumi, Org. Lett., 2005, 7, 163-165.
An operationally simple, tin-free reductive dehalogenation system allows the reduction of activated C-X bonds in good yields with excellent functional-group tolerance and chemoselectivity over aryl and vinyl C-X bonds in the presence of the well-known visible-light-activated photoredox catalyst Ru(bpy)3Cl2 in combination with iPr2NEt and HCO2H or Hantzsch ester as the hydrogen atom donor.
J. M. R. Narayanam, J. W. Tucker, C. R. J. Stephenson, J. Am. Chem. Soc., 2009, 131, 8756-8757.
Various di- and triarylfurans were prepared in high yields from but-2-ene-1,4-diones and but-2-yne-1,4-diones using formic acid in the presence of a catalytic amount of palladium on carbon in poly(ethylene glycol)-200 as solvent under microwave irradiation.
H. S. P. Rao, S. Jothilingam, J. Org. Chem., 2003, 68, 5392-5394.
Several aryl-substituted pyrrole derivates were prepared conveniently in a microwave-assisted one pot-reaction from but-2-ene-1,4-diones and but-2-yne-1,4-diones via Pd/C-catalyzed hydrogenation of the carbon-carbon double bond/triple bond followed by amination-cyclization.
H. S. P. Rao, S. Jothilingam, H. W. Scheeren, Tetrahedron, 2004, 60, 1625-1630.
The synthesis of 3,5-dimethyl-N-nitro-1-pyrazole-1-carboxamidine (DMNPC) has been optimised. A detailed protocol for the preparation of a range of guanidines via nitroguanidines is described using DMNPC as guanidinylating reagent.
J. A. Castillo-Meléndez, B. T. Golding, Synthesis, 2004, 1655-1663.