We have developed practical and efficient ruthenium catalysts for the transformation of terminal alkynes to linear alcohols and aldehydes.
Both catalysts tolerate a broad range of functional groups including esters, amides, alkenes, alcohols, carboxylic acids, alkyl halides, and tertiary amines. Reactions typically require 2–5 mol% catalyst to reach full conversion of substrate. Sterically-encumbered alkynes or those that contain strongly coordinating functional groups (such as unhindered alkenes and amines) require 5–10 mol% catalyst to obtain full conversion.
Some practical notes:
• Both catalysts are air-stable and can be stored under the benchtop without any special precautions.
• However, the intermediates formed under the reaction conditions are air-sensitive, thus it is essential that the reactions are conducted under anaerobic conditions.
• The reductive hydration catalyst is activated by the addition of formic acid. For difficult substrates, it may be advantageous to add a small amount of trifluoroacetic acid to the reaction mixture.
• The reductive hydration catalyst converts formic acid to dihydrogen and carbon dioxide. Accordingly, pressure will develop in a sealed vessel and appropriate precautions should be taken.
Le Li and Seth B. Herzon Nat. Chem. 2014, 6, 22.
Le Li, Mingshuo Zeng and Seth B. Herzon Angew. Chem., Int. Ed. 2014, 53, 7892.
Mingshuo Zeng, Le Li and Seth B. Herzon J. Am. Chem. Soc. 2014, 136, 7058.
Mingshuo Zeng and Seth B. Herzon J. Org. Chem. 2015, 80, 8604.
For a review, see: Mingshuo Zeng and Seth B. Herzon Aldrichimica Acta 2014, 47, 55.
See also: Le Li and Seth B. Herzon J. Am. Chem. Soc. 2012, 134, 17376.