Single step transformation of a carboxylic acid into an aldehyde

What are the different ways of transforming a carboxylic acid into an aldehyde in a single step ? (as opposed as for instance first transforming it to an ester then to an aldehyde)


The bottom of [this page](https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/crbacid2.htm#acderv) doesn't indicate any such way.


I am not looking for a "big-list", so the most common ways would be enough.




$\ce{Li, RNH2 (R=Me, Et)/NH4Cl/H3O+}$


* [Burgstahler, A. W.; Worden, L. R.; Lewis, T. B. Direct Reduction of Carboxylic Acids to Aldehydes by Lithium in Ethylamine. *J. Org. Chem.* **1963,** *28* (10), 2918–2919.](http://dx.doi.org/10.1021/jo01045a532)
* [Bedenbaugh, A. O.; Bedenbaugh, J. H.; Bergin, W. A.; Adkins, J. D. Synthesis of aldehydes and secondary amines from carboxylic acids via imines. *J. Am. Chem. Soc.* **1970,** *92* (19), 5774–5775.](http://dx.doi.org/10.1021/ja00722a060)


$\ce{BH3.SMe2/PCC}$


* [Brown, H. C.; Rao, C. G.; Kulkarni, S. U. A Convenient Conversion of Carboxylic Acids into Aldehydes. *Synthesis* **1979,** *1979* (9), 704–705.](http://dx.doi.org/10.1055/s-1979-28802)


$\ce{(CH3)2CHC(CH3)2BH2}$


* [Brown, H. C.; Heim, P.; Yoon, N. M. Selective reductions. XVII. Reaction of thexylborane in tetrahydrofuran with selected organic compounds containing representative functional groups. Comparison of the reducing characteristics of diborane and its alkyl derivatives. *J. Org. Chem.* **1972,** *37* (19), 2942–2950.](http://dx.doi.org/10.1021/jo00984a006)


$\ce{(CH3)2CHC(CH3)2BHCl.SMe2}$


* [Brown, H. C.; Cha, J. S.; Nazer, B.; Yoon, N. M. Exceptionally facile reduction of acyclic and alicyclic carboxylic acids to aldehydes by thexylchloroborane-dimethyl sulfide. *J. Am. Chem. Soc.* **1984,** *106* (25), 8001–8002.](http://dx.doi.org/10.1021/ja00337a075)
* [Brown, H. C.; Nazer, B.; Cha, J. S.; Sikorski, J. A. Selective reductions. 38. Reaction of thexylchloroborane-methyl sulfide complex in methylene chloride with selected organic compounds containing representative functional groups. Comparison of the reducing characteristics of thexylchloroborane, thexylborane, and diborane. *J. Org. Chem.* **1986,** *51* (26), 5264–5270.](http://dx.doi.org/10.1021/jo00376a040)
* [Brown, H. C.; Cha, J. S.; Yoon, N. M.; Nazer, B. Selective reductions. 39. Partial reduction of carboxylic acids with thexylchloroborane-methyl sulfide. A direct and simple aldehyde synthesis. *J. Org. Chem.* **1987,** *52* (24), 5400–5406.](http://dx.doi.org/10.1021/jo00233a018)


$\ce{(CH3)2CHC(CH3)2BHBr.SMe2}$


* [Cha, J. S.; Kim, J. E.; Lee, K. W. Facile reduction of saturated and unsaturated carboxylic acids and their salts to aldehydes by thexylbromoborane-dimethyl sulfide. *J. Org. Chem.* **1987,** *52* (22), 5030–5032.](http://dx.doi.org/10.1021/jo00231a037)
* [Cha, J. S.; Kim, J. E.; Oh, S. Y.; Lee, J. C.; Lee, K. W. Direct conversion of saturated and unsaturated carboxylic acids into aldehydes by thexylbromoborane-dimethyl sulfide. *Tetrahedron Letters* **1987,** *28* (21), 2389–2392.](http://dx.doi.org/10.1016/S0040-4039(00)96132-X)


9-BBN/Li 9-BBN


* [Cha, J. S.; Kim, J. E.; Oh, S. Y.; Kim, J. D. One-pot conversion of carboxylic acids to aldehydes through treatment of acyloxy-9-borabicyclo[3.3.1]nonanes with lithium 9-boratabicyclo[3.3.1]nonane. *Tetrahedron Letters* **1987,** *28* (39), 4575–4578.](http://dx.doi.org/10.1016/S0040-4039(00)96568-7)


9-BBN/*t*-BuLi/9-BBN


* [Cha, J. S.; Kim, J. E.; Kim, Y. S. One-pot transformation of carboxylic acids into aldehydes through stepwise treatment of acycloxy-9-borabicyclo[3.3.1]nonanes with Full-size image (<1 K)-butyllithium and 9-borabicyclo [3.3.1]nonane. *Tetrahedron Letters* **1987,** *28* (49), 6231–6234.](http://dx.doi.org/10.1016/S0040-4039(00)61855-5)


DIBAL-H


* Zakharkin, L. I.; Khorlina, I. M. *Zh. Obshch. Khim.* **1964** *34,* 1029; *J. Gen. Chem. USSR* **1964** *34,* 1021.


bis(*N*-methylpiperazinyl)aluminum hydride


* [Muraki, M.; Mukaiyama, T. Aminoaluminum hydride as new reducing agents. I. Selective reduction of carboxylic acids to aldehydes. *Chemistry Letters* **1974,** *3* (12), 1447–1450.](http://doi.org/10.1246/cl.1974.1447)
* [Hubert, T. D.; Eyman, D. P.; Wiemer, D. F. A convenient synthesis of bis(*N*-methylpiperazinyl)aluminum hydride: a reagent for the reduction of carboxylic acids to aldehydes. *J. Org. Chem.* **1984,** *49* (12), 2279–2281.](http://dx.doi.org/10.1021/jo00186a038)


activated silyl carboxylates


* [Corriu, R. J. P.; Lanneau G. F.; Perrot M. The one-pot conversion of carboxylic acids to aldehydes via activated silyl carboxylates. *Tetrahedron Letters* **1987,** *28* (34), 3941–3944.](http://dx.doi.org/10.1016/S0040-4039(00)96426-8)


titanium-catalyzed Grignard


* [Sato, F.; Jinbo, T.; Sato, M. The Reduction of Carboxylic Acids to Aldehydes by Dichlorobis[π-cyclopentadienyl]titanium-Catalyzed Grignard Reactions. *Synthesis* **1981,** *1981* (11), 871](http://dx.doi.org/10.1055/s-1981-29623)


*N*,*N*-dimethylchloromethyleniminium chloride and lithium tri-*t*-butoxyaluminum hydride


* [Fujisawa, T.; Mori, T.; Tsuge, S.; Sato, T. Direct and chemoselective conversion of carboxylic acids into aldehydes. *Tetrahedron Letters* **1983,** *24* (14), 1543–1546.](http://dx.doi.org/10.1016/S0040-4039(00)81704-9)


$o\text{-}\ce{HSC6H4OH, POCl3, HClO4/LiAlH4/H2O, HgCl2}$


* [Costa, L.; Degani, I.; Fochi, R.; Tundo, P. Pentaatomie heteroaromatic cations. Note III. A Convenient Synthesis of Aldehydes from Carboxylic Acids via 2-Substituted 1,3-Benzoxathiolium Perchlorates. *J. Heterocyclic Chem.* **1974,** *11,* 943–948.](http://dx.doi.org/10.1002/jhet.5570110616)


$o\text{-}\ce{(NH2)C6H4, PPA/NaOet/MeI/NaBH4}$ or $\ce{LiAlH4/H3O+}$


* [Craig, J. C.; Ekwurire, N. N.; Fu, C. C.; Walker, K. A. M. Conversion of Carboxylic Acids into Aldehydes and their C-1 or C-2 Deuteriated Derivatives. *Synthesis* **1981,** *1981* (4), 303–305.](http://dx.doi.org/10.1055/s-1981-29428)


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