Borrowing hydrogen

Borrowing hydrogen catalysis is an important catalytic concept that is based on the intermediate oxidation of an alcohol substrate to the corresponding aldehyde by the catalyst (which "borrows" hydrogen from the substrate); the intermediate aldehyde then reacts with e.g. a secondary amine in a condensation reaction to produce e.g. an imine, that is then reduced by the catalyst in the final step to yield e.g. a tertiary amine.^[1][2][3] The method is highly atom economic, because is circumvents the activation of the alcohol (which is a poor electrophile itself, see tosylation or Swern oxidation). "Borrowing hydrogen" can be seen as an example of sustainable (thus "green") chemistry. The method is not limited to the preparation of amines, it can also be used to form C–C-bonds.^[4]

See also

• (Cymene)ruthenium dichloride dimer
• Dichlorotris(triphenylphosphine)ruthenium(II)
• dppf
• Eschweiler-Clarke reaction

References

1. ^ Hamid, Malai Haniti S. A.; Slatford, Paul A.; Williams, Jonathan M. J. (2007). "Borrowing Hydrogen in the Activation of Alcohols". Advanced Synthesis & Catalysis 349 (10): 1555. doi:10.1002/adsc.200600638. 
2. ^ M. Hamid (2008). Conversion of Alcohols into Amines by Borrowing Hydrogen (Ph.D. thesis). University of Bath. http://opus.bath.ac.uk/15587/1/UnivBath_PhD_2008_MHSA_Hamid.pdf. 
3. ^ D. Hollmann (2008). New Applications of the Borrowing Hydrogen Methodology — Selective Synthesis of Amines and Mechanistic Studies (Dr. rer. nat. thesis). http://deposit.ddb.de/cgi-bin/dokserv?idn=993351522&dok_var=d1&dok_ext=pdf&filename=993351522.pdf. 
4. ^ Pridmore, Simon J.; Williams, Jonathan M.J. (2008). "C–C bond formation from alcohols and malonate half esters using borrowing hydrogen methodology". Tet. Lett. 49 (52): 7413. doi:10.1016/j.tetlet.2008.10.059.