Highly Enantioselective Dihydroxylation of 1,1-Disubstituted Aliphatic Alkenes Enabled by Orchestrated Noncovalent π-Interactions.

The elusive nature of noncovalent π-interactions leads to their infrequent use as a design element in challenging chemical reactions. Stereocontrolling models based on coordinated noncovalent π-interactions were used for the asymmetric dihydroxylation of 1,1-disubstituted aliphatic alkenes. By introduction of a substituted phthalazine ring into the alkene substrates, the enantioselectivity reached 99% under the catalysis of bis-cinchona alkaloid ligands. Density functional theory calculations indicated a well-orchestrated, π-π interaction-directed "sandwich-like" transition state.

Unexpected Observation of Heavy Monomeric Motifs in a Basket-like Au26Ag22 Nanocluster.

Herein, a new basket-like Au26Ag22(TBBT)30 nanocluster (where TBBT = 4- tert-butylthiophenol) was synthesized by a coreduction method. Also, the precise structure was characterized by single-crystal X-ray diffraction and displays a shell-by-shell construction with a Au12@AuAg19 kernel protected by a Au13S26@Ag3S4 surface motif. Interestingly, a handle-like Ag3S4 motif was observed that composes the outermost shell. Except for this Ag3S4 motif, the other motifs are all monomeric "-S-Au-S-" motifs, which are rarely reported in thiolate-capped metal (Au or Ag) nanoclusters with small size ( n < 60). This work will provide new insight into the growth pattern of thiolate-capped metal nanoclusters.