Categories: C-H Bond Formation >
Reduction of carboxyl compounds to aldehydes
A highly efficient in situ generation of the Schwartz reagent provides a convenient method for the reduction of amides to aldehydes and the regioselective hydrozirconation-iodination of alkynes and alkenes. These single-step processes proceed in very short reaction time, show excellent functional group compatibility, and use inexpensive and long-storage stable reducing reagents.
Y. Zhao, V. Snieckus, Org. Lett., 2014, 16, 390-393.
A chemoselective activation of a secondary amide with triflic anhydride in the presence of 2-fluoropyridine enables a mild reduction using triethylsilane, a cheap and rather inert reagent. Imines can be isolated after a basic workup or readily transformed to the aldehydes following an acidic workup. The amine moiety can be accessed by addition of Hantzsch ester to the reaction mixture.
G. Pelletier, W. S. Bechara, A. B. Charette, J. Am. Chem. Soc., 2010, 132, 12817-12819.
A palladium-catalyzed reduction of 2-pyridinyl esters using hydrosilanes is applicable to the preparation of aliphatic, aromatic, and α,β-unsaturated aldehydes. Various functional groups, such as fluoro, methoxy, aldehyde, acetal, and ester, are tolerated.
J. Nakanishi, H. Tatamidani, Y. Fukumoto, N. Chatani, Synlett, 2006, 869-872.
Treatment of ethanethiol esters with triethylsilane and palladium on carbon at ambient temperature furnished aldehydes. In addition, a variety of ketones has been prepared by a palladium-catalyzed reaction of ethanethiol esters with organozinc reagents. Both transformations tolerate various functional groups, including esters, ketones, aromatic halides and aldehydes.
H. Tokuyama, S. Yokoshima, T. Yamashita, S.-C. Lin, L. Li, T. Fukuyama, J. Braz. Chem. Soc., 1998, 9, 381-387.
Reduction of ethanethiol esters of α-amino acids to α-amino aldehydes by triethylsilane and catalytic palladium-on-carbon is described. α-Amino aldehydes with Boc, Cbz, or Fmoc protection could be obtained without racemization in high yield.
H. Tokuyama, S. Yokoshima, S.-C. Lin, L. Li, T. Fukuyama, Synthesis, 2002, 1121-1123.