Isolation, characterization, and reaction of activated iodosylbenzene monomer hydroxy(phenyl)iodonium ion with hypervalent bonding: supramolecular complex PhI+OH.18-crown-6 with secondary I...O interactions

The isolation, characterization, and reaction of the active species hydroxy(phenyl)iodonium ion with hypervalent bonding are reported. Reaction of iodosylbenzene with HBF(4)-Me(2)O in the presence of equimolar 18-crown-6 in dichloromethane afforded the hydroxy-lambda(3)-iodane complex PhI(OH)BF(4).18-crown-6 as stable yellow prisms. X-ray structure analysis indicated that both the close contacts between the iodine(III) and the three adjacent oxygen atoms of 18-crown-6, and the hydrogen bonding OH.O(crown ether) will be responsible for the increased stability of the complex as compared to the uncomplexed PhI(OH)BF(4). The crown ether complex is highly reactive and serves as a versatile oxidant even in water: thus, the complex undergoes oxidative transformations of a variety of functional groups such as olefins, alkynes, enones, silyl enol ethers, sulfides, and phenols under mild conditions.     

Tandem Michael addition-carbene insertion reaction of 1-alkynyl(aryl)(tetrafluoroborato)-lambda3-bromanes: 1-(phenylsulfonyl)- and 1-(trifluoromethylsulfonyl)cyclopentene annulation

Exposure of 1-alkynyl[p-(trifluoromethyl)phenyl](tetrafluoroborato)-lambda(3)-bromanes to sodium benzenesulfinate or sodium trifluoromethanesulfinate in dichloromethane at 0 degree C under argon resulted in tandem Michael-carbene insertion reactions to produce 1-sulfonylcyclopentenes selectively, with concomitant formation of a small amount of rearranged 1-alkynyl sulfones.     

Emergence of BLOCH bands in a rotating Bose-Einstein condensate

A rotating Bose-Einstein condensate is shown to exhibit a Bloch band structure even in the absence of a periodic potential. Vortices enter the condensate via Bragg reflection if the frequency of a rotating drive is adiabatically increased or decreased, or if the interaction is adiabatically changed at a constant rotating drive. A localized state analogous to a gap soliton in a periodic system is predicted to occur near the edge of the Brillouin zone.     

Shaping Carbon Nanotubes with Chemistry

As-grown, string-shaped single-walled carbon nanotubes were transformed into other shapes by applications of organic chemistry. Cutting carbon nanotubes in strong acids affords oxygen-containing groups at both ends of the open tubes. These groups were utilized for ring-closure reactions in very dilute conditions. Atomic force microscopy reveals ring-shaped nanotubes with a mean diameter of 540 nm as products. Also, the end groups were used to react with the surface amine groups of PAMAM dendrimer. It gave star-shaped structures in which straight nanotubes are radiating from dendrimer centers. These experiments clearly demonstrate that covalent chemistry is useful for construction of super-structured carbon nanotubes.     

New Integrable Models from the Gauge/YBE Correspondence

We introduce a class of new integrable lattice models labeled by a pair of positive integers N and r. The integrable model is obtained from the Gauge/YBE correspondence, which states the equivalence of the 4d $\mathcal {N} =1$ $S^{1}\times S^{3}/ \mathbb {Z} _{r}$ index of a large class of SU(N) quiver gauge theories with the partition function of 2d classical integrable spin models. The integrability of the model (star-star relation) is equivalent with the invariance of the index under the Seiberg duality. Our solution to the Yang-Baxter equation is one of the most general known in the literature, and reproduces a number of known integrable models. Our analysis identifies the Yang-Baxter equation with a particular duality (called the Yang-Baxter duality) between two 4d $\mathcal {N} =1$ supersymmetric quiver gauge theories. This suggests that the integrability goes beyond 4d lens indices and can be extended to the full physical equivalence among the IR fixed points.     

Electronic Tuning of Iron–Oxo‐Mediated C?H Activation: Effect of Electron‐Donating Ligand on Selectivity

We have reported previously that an iron(III) complex supported by an anionic pentadentate monoamido ligand, dpaq^H (dpaq^H=2‐[bis(pyridin‐2‐ylmethyl)]amino‐N‐quinolin‐8‐yl‐acetamido), promotes selective C? H hydroxylation with H₂O₂ with high regioselectivity. Herein, we report on the preparation of Fe^III–dpaq derivatives that have a series of substituent groups at the 5‐position of a quinoline moiety in the parent ligand dpaq^H (dpaq^R, R: OMe, H, Cl, and NO₂), and examine them with respect to their catalytic activity in C? H hydroxylation with H₂O₂. As the substituent group becomes more electron‐withdrawing, both the selectivity and the turnover number increase, but the selectivity of epoxidation shows the opposite trend.