Synthesis and Characterization of Bimetallic Nanoclusters Stabilized by Chiral and Achiral Polyvinylpyrrolidinones. Catalytic C(sp 3 )-H Oxidation.

Second-generation chiral-substituted poly- N -vinylpyrrolidinones (CSPVPs) (-)- 1R and (+)- 1S were synthesized by free-radical polymerization of (3a R ,6a R )- and (3a S ,6a S )-5-ethenyl-tetrahydro-2,2-dimethyl-4 H -1,3-dioxolo[4,5- c ]pyrrol-4-one, respectively, using thermal and photochemical reactions. They were produced from respective d -isoascorbic acid and d-ribose. In addition, chiral polymer (-)- 2 was also synthesized from the polymerization of ( S )-3-(methoxymethoxy)-1-vinylpyrrolidin-2-one. Molecular weights of these chiral polymers were measured using HRMS, and the polymer chain tacticity was studied using 13 C NMR spectroscopy. Chiral polymers (-)- 1R , (+)- 1S , and (-)- 2 along with poly- N -vinylpyrrolidinone (PVP, MW 40K) were separately used in the stabilization of Cu/Au or Pd/Au nanoclusters. CD spectra of the bimetallic nanoclusters stabilized by (-)- 1R and (+)- 1S showed close to mirror-imaged CD absorption bands at wavelengths 200-300 nm, revealing that bimetallic nanoclusters' chiroptical responses are derived from chiral polymer-encapsulated nanomaterials. Chemo-, regio-, and stereo-selectivity was found in the catalytic C-H group oxidation reactions of complex bioactive natural products, such as ambroxide, menthofuran, boldine, estrone, dehydroabietylamine, 9-allogibberic acid, and sclareolide, and substituted adamantane molecules, when catalyst Cu/Au (3:1) or Pd/Au (3:1) stabilized by CSPVPs or PVP and oxidant H 2 O 2 or t -BuOOH were applied. Oxidation of (+)-boldine N -oxide 23 using NMO as an oxidant yielded 4,5-dehydroboldine 27 , and oxidation of (-)-9-allogibberic acid yielded C6,15 lactone 47 and C6-ketone 48 .