Pd-0-Catalyzed Asymmetric Carbonitratation Reaction Featuring an H-Bonding-Driven Alkyl-Pd-II-ONO2 Reductive Elimination

Reductive elimination of alkyl-Pd-II-O is a synthetically useful yet underdeveloped elementary reaction. Here we report that the combination of an H-bonding donor [PyH][BE4] and AgNO3 additive under toluene/H2O biphasic system can enable such elementary step to form alkyl nitrate. This results in the Pd-0-catalyzed asymmetric carbonitratations of (Z)-1-iodo-1,6-dienes with (R)-BINAP as the chiral ligand, affording alkyl nitrates up to 96 % ee. Mechanistic studies disclose that the reaction consists of oxidative addition of Pd-0 catalyst to vinyl iodide, anion ligand exchange between I- and NO3-, alkene insertion and S(N)2-type alkyl-Pd-II-ONO2 reductive elimination. Evidences suggest that H-bonding interaction of PyH center dot center dot center dot ONO2 can facilitate dissociation of O2NO- ligand from the alkyl-Pd-II-ONO2 species, thus enabling the challenging alkyl-Pd-II-ONO2 reductive elimination to be feasible.

Automated summary

In this study, the combination of an H-bonding donor [PyH][BE4] and AgNO3 additive under a toluene/H2O biphasic system was found to enable the reductive elimination of alkyl-Pd-II-O, forming alkyl nitrate. The Pd-0-catalyzed asymmetric carbonitration of (Z)-1-iodo-1,6-dienes using (R)-BINAP as the chiral ligand provided alkyl nitrates with up to 96% ee. Mechanistic studies revealed that the reaction involves oxidative addition, anion ligand exchange, alkene insertion, and S(N)2-type reductive elimination of alkyl-Pd-II-ONO2.