A gold-catalyzed intermolecular reaction of propiolic acids with alkenes led to a [4 + 2] annulation or enyne cross metathesis. The [4 + 2] annulation proceeds with net cis-addition with respect to alkenes and provides an expedient route to α,β-unsaturated δ-lactones, for which preliminary asymmetric reactions were also demonstrated. For 1,2-disubstituted alkenes, unprecedented enyne cross metathesis occurred to give 1,3-dienes in a completely stereospecific fashion. DFT calculations and experiments indicated that the cyclobutene derivatives are not viable intermediates and that the steric interactions during concerted σ-bond rearrangements are responsible for the observed unique stereospecificity.

A biofilm, a community of microorganisms, is highly resistant to antibiotics, resulting in massive losses in various areas. We herein present a strategy to remove Streptococcus mutans biofilms through a spontaneous exfoliation by the synergistic effect between zwitterion and sugar alcohols. It is assumed that the anionic site of zwitterion can be coupled with sugar alcohols and the cationic site remains in the state of lacking electrons. The cationic site allows the complexes to be delivered to negatively charged exopolysaccharides of biofilms. This strategy facilitates a significant increase in the ability of sugar alcohols to disperse aggregated exopolysaccharides. In this work, it was demonstrated that the mixture of betaine and erythritol existed as a complex in water and that the complex induced a spontaneous detachment of biofilms from the surface to which the biofilms had been adhered. This detachment resulted from a reduction in adhesive forces of the biofilms due to an increase in solubility of bacterial exopolysaccharides. The effects triggered by the formation of complex between zwitterion and sugar alcohol provide a simple and safe way to remove biofilms without antibiotics and physical forces.

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Gold-catalyzed aerobic oxygenative cleavage of triple bonds that occurs under the ambient pressure of air and at room temperature is reported; radical inhibition tests suggest that oxygenation occurs via a gold-bound metalloradical intermediate.

Asymmetric hydrosilylation was one of the most effective methods, which provided optically active organosilanes as a synthetically useful intermediate in organic synthesis. 1 One useful transformation is the Tamao-Fleming oxidation, which is an oxidation reaction of carbon silicone bond to afford optically active alcohols with retention of configuration. 2 Palladium-monophosphorus ligand complex is the wellknown catalysts in asymmetric hydrosilylation of olefins. Among various types of monophosphines, the monodentate phosphine (MOP)-type ligands were known as a highly reactive and enantioselective ligands. 3 Ferrocene-based monophosphine ligands such as L1 were also highly effective ligands in asymmetric hydrosilylation of olefins ( Figure 1). 4 Recently, chiral phosphoramidite ligands which were easily prepared from readily available compounds with a good stability 5 were applied to asymmetric hydrosilylation of styrene and its derivatives. 6 As well as the Feringa ligand (L2), 6a phosphoramidites which had 1,1 0spirobiindane backbone 6b or BINOL backbone with unsymmetric secondary amines 6c demonstrated that these ligands were highly efficient for the Pd-catalyzed asymmetric hydrosilylation of styrenes. Chiral phosphoramidite ligands (L3a) derived from bis((R)-1-ferrocenylethyl)amine, introduced by Zheng and co-workers, were used in the Cucatalyzed asymmetric 1,4-conjugate addition. 7 Thus, we attempted to prepare whole diastereomers of the ferrocenyl amines and to prepare all the phosphoramidite ligands from (S)-BINOL and these diastereomeric ferrocenyl amines in order to evaluate their utility in asymmetric hydrosilylation of styrenes as a chiral ligand, focusing on the effect of the diastereomeric ferrocenyl amino group on the ligands in their enantioselectivity. In this context, we synthesized all the diastereomeric phosphoramidites from (S)-BINOL and diastereomeric bis(1-ferrocenylethyl)amines. Two racemic (R,R)and (S,S)-4 and one meso (R,S)-4 were obtained by the substitution reaction between the appropriate ammonium salt 2 and the primary amine 3, respectively, starting from each of enantiomerically pure N,N-dimethylaminoethylferrocene (1). 7,8 Diastereomeric phosphoramidite ligands L3 were easily prepared from (S)-BINOL, bis(1-ferrocenylethyl)amines 4, and PCl 3 in the presence of trimethylamine (Scheme 1).With these phosphoramidite ligands in hands, we examined the reactivity and enantioselectivity of the hydrosilylation of styrene (5a) using these diastereomeric ferrocenyl phosphoramidite ligands ( Table 1). The catalytic reactions were performed without solvent with 1.0 mol % of palladium catalysts generated in situ by mixing [PdCl(π-C 3 H 5 )] 2 and L3 (Pd/P = 1/2). The reactions proceeded smoothly at 20 C in 20 h to give optically active 1-phenyl-1-(trichlorosilyl)ethane (6a). After Tamao-Fleming oxidation, enantioselectivities of the hydrosilylation were deduced from enantiomeric excess of 1-phenylethan-1-ol (7a). It was found that (S a ,R c ,R c ,)-L3a, which had the same absolute configuration...