The catalytic, diastereo- and enantioselective Mannich-type reaction of a hydrazono ester with silyl enol ethers in aqueous media has been successfully achieved with ZnF(2), a chiral diamine ligand, and trifluoromethanesulfonic acid.
Radio Frequency Identification (RFID) and sensor networks are both wireless technologies that provide limitless future potentials. While the industry has witnessed rapid growth in developing and applying RFID technology, and the network research community has devoted tremendous efforts in sensor networks, these two communities would benefit greatly by learning from each other. In pursuing this effect, a project utilizing and integrating both technologies is described. The goal is to build an in-home elder healthcare system that monitors patients' medication in take. This would help addressing the challenge of a growing aging population.
Catalytic asymmetric aldol reactions in aqueous media have been developed using Pr(OTf)(3) and chiral bis-pyridino-18-crown-6 1. In the asymmetric aldol reaction using rare earth metal triflates (RE(OTf)(3)) and 1, slight changes in the ionic diameters of the metal cations greatly affected the diastereo- and enantioselectivities of the products. The substituents (MeO, Br) at the 4-position of the pyridine rings of the crown ether did not significantly affect the selectivities in the asymmetric aldol reaction, although they affected the binding ability of the crown ether with RE cations and the catalytic activity of Pr(OTf)(3)-crown ether complexes. From X-ray structures of RE(NO(3))(3)-crown ether complexes, it was found that they had similar structures regardless of the RE cations and the crown ethers used. Accordingly, the binding ability of the crown ether with the RE cation and the catalytic activity of the complex are important for attaining high selectivity in the asymmetric aldol reaction. Various aromatic and alpha,beta-unsaturated aldehydes and silyl enol ethers derived from ketones and a thioester can be employed in the catalytic asymmetric aldol reactions using Pr(OTf)(3) and 1, to provide the aldol adducts in good to high yields and stereoselectivities. In the case using the silyl enol ether derived from the thioester, 2,6-di-tert-butylpyridine significantly improved the yields of the aldol adducts.
Catalytic asymmetric hydroxymethylation of silicon enolates has been achieved. In this reaction, an aqueous solution of formaldehyde can be used to realize an easy and safe procedure, and high enantioselectivities have been obtained. This is the first example of catalytic asymmetric reactions in aqueous media with a chiral scandium complex.
We have developed Zn-catalyzed asymmetric allylation of hydrazono esters with allylboronates. The reactions proceeded smoothly in high yields and high stereoselectivities. Remarkably, formal α-addition occurred for α-substituted allylboronates exclusively, and excellent stereoselectivities were observed. This is the first example of catalytic regio- and stereoselective allylations with formal α-addition. In addition, the reaction proceeded in aqueous media, and the use of water is essential. Zn(OH)2 might be a catalyst in this asymmetric allylation, and the catalytic activity of Zn(OH)2 was confirmed. This is also the first case of chiral metal hydroxide-catalyzed asymmetric reactions.
[reaction: see text] Catalytic asymmetric hydroxymethylation of silicon enolates with an aqueous formaldehyde solution has been developed using a chiral bismuth complex. This is the first example of highly enantioselective reactions using a chiral bismuth catalyst in aqueous media. In this paper, we have added Bi(OTf)(3)-1 complex as a "water-compatible Lewis acid". Bi(OTf)3 is unstable in the presence of water but is stabilized by the basic ligand.
[figure: see text] Catalytic asymmetric aldol reactions catalyzed by lanthanide trifluoromethanesulfonates in aqueous media have been realized for the first time using a chiral crown ether.
This article reports the first psychological evidence that the combination of
oscillating optic flow and synchronous foot vibration evokes a walking
sensation. In this study, we first captured a walker’s first-person-view scenes
with footstep timings. Participants observed the naturally oscillating scenes on
a head-mounted display with vibrations on their feet and rated walking-related
sensations using a Visual Analogue Scale. They perceived stronger sensations of
self-motion, walking, leg action, and telepresence from the oscillating visual
flow with foot vibrations than with randomized-timing vibrations or without
vibrations. The artificial delay of foot vibrations with respect to the scenes
diminished the walking-related sensations. These results suggest that the
oscillating visual scenes and synchronous foot vibrations are effective for
creating virtual walking sensations.
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