Catalytic Asymmetric Diels-Alder Reaction of 2'-Hydroxychalcone as a Dienophile with a VANOL-Borate Ester Complex.

Numerous flavonoid Diels-Alder-type natural products have been isolated and received great attention from the synthetic community. Herein, we reported a catalytic strategy for an asymmetric Diels-Alder reaction of 2'-hydroxychalcone with a range of diene substrates using a chiral ligand-boron Lewis acid complex. This method enables the convenient synthesis of a wide range of cyclohexene skeletons in excellent yields with moderate to good enantioselectivities, which is critical to prepare natural product congeners for further biological studies.

Construction of microbelts through the coassembly of a disclike molecule and primary alkyl ammoniums: a noncovalent strategy to mimic covalently bonded pi-core alkyl chain structure.

In this letter, we report the fabrication of microbelts through the coassembly of hexa-2-pyridyl-hexaazatriphenylen (HPHAT), a disklike pi-conjugated molecule, with primary alkyl ammonium triflate. The strategy is first to construct hydrogen-bonded complexes between HPHAT and primary alkyl ammoniums to mimic covalently bonded pi-core alkyl chain structures, and then the complexes self-assemble into microbelts driven by pi-pi stacking in the pi core and van der Waals interactions between the peripheral alkyl chains. The morphology of as-prepared microbelts has been characterized with scanning electron microscopy (SEM), optical microscopy, polarizing microscopy, and transmission electron microscopy (TEM). Spectroscopic and crystallographic investigations were also carried out to reveal the formation mechanism of the microbelts, through which a sequential self-assembly process has been proposed.

Self-assembly of porphyrin-azulene-porphyrin and porphyrin-azulene conjugates.

In this paper we report the synthesis and self-assembling behavior of new porphyrin-azulene-porphyrin and porphyrin-azulene conjugates. The porphyrin-azulene-porphyrin conjugate gelates a number of organic solvents, while the porphyrin-azulene conjugates form vesicles in a chloroform-methanol binary mixture. The structures of the organogels and vesicles have been characterized by SEM and AFM. Two porphyrin-naphthalene-porphyrin and porphyrin-naphthalene conjugates were also prepared. A comparison of their properties with those of the azulene analogues reveals that the intermolecular dipole-dipole interaction of the azulene units plays an important role in promoting the self-assembly of the porphyrin-azulene-porphyrin and porphyrin-azulene conjugates.

Self-assembly of chiral propeller-like supermolecules with unusual "sergeants-and-soldiers" and "majority-rules" effects.

Chiral amplification is an interesting phenomenon in supramolecular chemistry mainly observed in complicated systems in which cooperative effect dominate. Herein, chiral, supramolecular, propeller-like architectures have been constructed through coassembly of an achiral disk-shaped molecule and chiral amino acid derivatives driven by intermolecular hydrogen bonding. Both the "sergeants-and-soldiers" principle and "majority-rules" effect are applicable in these discrete four-component supermolecules, which are the simplest supramolecular system ever reported that exhibit chiral amplification.