title: Nucleophilic β-Carbon Activation of Propionic Acid as a 3-Carbon Synthon by Carbene Organocatalysis.
abstract: Direct β-carbon activation of propionic acid (C2H5CO2H) by carbene organocatalysis has been developed. This activation affords the smallest azolium homoenolate intermediate (without any substituent) as a 3-carbon nucleophile for enantioselective reactions. Propionic acid is an excellent raw material because it is cheap, stable, and safe. This approach provides a much better solution to azolium homoenolate synthesis than the previously established use of acrolein (enal without any substituent), which is expensive, unstable, and toxic.
authors.affiliation: Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore).
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Jin
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637371 (Singapore).
authors.forename: Ke
authors.initials: K
authors.lastname: Jiang
authors.affiliation: Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore).
authors.forename: Zhenqian
authors.initials: Z
authors.lastname: Fu
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore 637371 (Singapore).
authors.forename: Jaume
authors.initials: J
authors.lastname: Torres
authors.affiliation: Laboratory Breeding Base of Green Pesticide and Agricultural, Bioengineering, Key Laboratory of Green Pesticide and Agricultural, Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang 550025 (P. R. China).
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Zheng
authors.affiliation: Laboratory Breeding Base of Green Pesticide and Agricultural, Bioengineering, Key Laboratory of Green Pesticide and Agricultural, Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang 550025 (P. R. China).
authors.forename: Song
authors.initials: S
authors.lastname: Yang
authors.affiliation: Laboratory Breeding Base of Green Pesticide and Agricultural, Bioengineering, Key Laboratory of Green Pesticide and Agricultural, Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang 550025 (P. R. China). songbaoan22@yahoo.com.
authors.forename: Bao-An
authors.initials: BA
authors.lastname: Song
authors.affiliation: Laboratory Breeding Base of Green Pesticide and Agricultural, Bioengineering, Key Laboratory of Green Pesticide and Agricultural, Bioengineering, Ministry of Education, Guizhou University, Huaxi District, Guiyang 550025 (P. R. China). robinchi@ntu.edu.sg.
authors.forename: Yonggui Robin
authors.initials: YR
authors.lastname: Chi
keywords: N-heterocyclic carbenes; asymmetric synthesis; organocatalysis; propionic acid; β-activation