Iridium-catalyzed asymmetric hydrogenation of racemic α-substituted lactones to chiral diols

Abstract

A protocol for the highly efficient iridium-catalyzed asymmetric hydrogenation of racemic α-substituted lactones via dynamic kinetic resolution is described.

Dual Photoredox/Copper Catalysis for the Remote C(sp3)−H Functionalization of Alcohols and Alkyl Halides by N‐Alkoxypyridinium Salts

“…The(S)absolute configuration of 6a was determined by its conversion to the known (S)-2phenylpentane-1,5-diol (11)and by comparing the sign of the optical rotations. [30] To gain insight on the reaction mechanism, several control experiments were conducted. Reaction of 4a with TMSN 3 failed to produce 5a in the absence of either one of the following ingredients, fac-Ir(ppy) 3 ,C uOAc or irradiation.…”

Unexpected CNN-to-CC Ligand Rearrangement in Pincer–Ruthenium Precatalysts Leads to a Base-Free Catalyst for Ester Hydrogenation

“…The ability to hydrogenate esters in the absence of an added strong base may be useful when base has the potential to cause undesired side reactions. For example, alkoxide bases are known to catalyze the racemization of α-chiral esters, which has been exploited in the dynamic kinetic resolution of racemic esters via hydrogenation. , However, if the ester reactant is enantiopure, a loss of optical purity would be detrimental. Kuriyama and co-workers have reported the use of a preactivated catalyst in the hydrogenation of α-chiral esters with minimal loss of optical purity .…”

Structure–Function Relationship in Ester Hydrogenation Catalyzed by Ruthenium CNN-Pincer Complexes

“…This suggests that with further experimentation, it may be possible to develop effective conditions for the hydrogenation of amides and/or nitriles with our catalyst system. The reactivity of catalysts for ester hydrogenation toward nonpolar substrates such as alkenes and alkynes is varied, although some catalysts have been shown to be highly specific for ester hydrogenation in the presence of both terminal and internal (nonconjugated) alkenes. , We are aware of one example of an ester hydrogenation catalyst that is tolerant of internal alkynes, reported by Clarke and co-workers . Under our optimized conditions for ester hydrogenation, Ru-dipp-Et catalyzed the complete hydrogenation of both 1-dodecene and 1-dodecyne to n -dodecane, indicating that it is not selective for CO bonds over CC bonds.…”