Synthesis of α-Hydroxy Acids via Dehydrogenative Cross-Coupling of a Sustainable C 2 Chemical (Ethylene Glycol) with Alcohols.

Ir(NHC) (NHC, N -heterocyclic carbene)-catalyzed dehydrogenative coupling of sustainable ethylene glycol and various bioalcohols can produce industrially valuable α-hydroxy acids (AHAs). This study is the first to report the sustainable synthesis of higher C n AHAs, in addition to glycolic acid (C 2 AHA) and lactic acid (C 3 AHA). This catalytic system can be recycled to the seventh cycle while maintaining good yields. A reaction mechanism, including facile dehydrogenation of each alcohol and fast cross-coupling of dehydrogenated aldehydes forming products, was proposed based on 18 O- and 2 H-labeling experiments and electron spray ionization-mass spectrometry (ESI-MS) and NMR spectral analyses.