Noncoordinating Dendrimer Polyanions: Cocatalysts for the Metallocene-Catalyzed Olefin Polymerization

Hexadentate poly-Lewis acids based on the bowl-shaped tribenzotriquinacene

Hexadentate poly-Lewis acids (PLA) based on the bowl-shaped tribenzotriquinacene (TBTQ) have been synthesised. The introduction of three n-propyl groups into the benzhydrylic positions of the TBTQ backbone has significantly increased the solubility of the subsequently derived compounds. Semi-flexible PLAs containing boron and aluminium were obtained by hydrometallation of the corresponding 2,3,6,7,10,11-hexaalkynyl-TBTQ. Other rigid hexadentate PLAs were synthesised by stannylation of the corresponding alkyne units with Me3SnNMe2 followed by tin-element exchange reactions. The Lewis acidity of these PLAs was investigated in host-guest experiments with pyridine. Further experiments with bidentate bases showed correlations between their flexibility, their Lewis basicity and the complexation behaviour towards the synthesised PLAs. Addition of bis((dimethylphosphino)methyl)dimethylsilane (BisPhos) to solutions of the rigid alkynyl PLAs led to the formation of 3 : 1 adducts. Single crystal X-ray diffraction was used to further elucidate the host-guest connectivtiy. In addition, a sixfold pnictogen-bonding donor was synthesised by tin-antimony exchange.

Synthesis of bi- and tetradentate poly-Lewis acids by hydroalumination of poly-alkynyl-anthracene derivatives

Photo-dimers of 1,5-diethynylanthracene and 1,5-bis[(trimethylsilyl)ethynyl]anthracene, obtained by UV radiation of the monomers, were treated with the bulky aluminium hydride [(SiMe₃)₂HC]₂AlH in hydroalumination reactions. Hydroalumination of the tetraethynyl-substituted anthracene photo-dimers (syn and anti) led to fourfold aluminium-functionalized Janus-like products with two aluminium functions on each side oriented towards the same direction. The reactions of the monomeric anthracene derivatives with [(SiMe₃)₂HC]₂AlH afforded semi-flexible bidentate Lewis acids, which are interesting building blocks for molecular chains bearing multiple Lewis-acidic functions. The aluminium-functionalized anti-photo-dimer was treated with various donor molecules to gain insight into its host-guest chemistry. All poly-Lewis acids and their adducts were characterized by X-ray diffraction experiments, multinuclear NMR spectroscopy and by elemental analyses.

Enantioselective Diels-Alder reaction of anthracene by chiral tritylium catalysis

The combination of the trityl cation and a chiral weakly coordinating Fe(III)-based bisphosphate anion was used to develop a new type of a highly active carbocation Lewis acid catalyst. The stereocontrol potential of the chiral tritylium ion pair was demonstrated by its application in an enantioselective Diels–Alder reaction of anthracene.

Synthesis of Polyamide Dendrimers bearing Multiple Hydrogen Bonding Parts on the Periphery

A series of polyamide dendrimers (GO-G2) having carboxy1 groups on the periphery were prepared by the divergent method. The reaction of G 18NH2 dendrimer with glutaric acid anhydride gave polyamide dendrimer (Gi-8COOH). The structure of polyamide dendrimers were confirmed by IR, 1H, 13C NMR, MALDI-TOF mass, and elemental analysis. Poly(4-vinylpyridine) (P4VP) was prepared by atom transfer radical polymerization of 4-vinylpyridine. A hydrogen bonded GI-8COOH/P4VP 1/8 (molar ratio) complex was prepared by mixing GIA8COOH with P4VP in methanol, followed by removing the solvent. IR spectrum of Gl-8COOH/P4VP 1/8 complex showed the characteristic absorptions at 2550 and 1950 cm-1 due to the hydrogen bonding. A glass transition temperature (Tg) of GI-8COOH/P4VP 1/8 complex was observed at 177°C by DSC measurement, whereas the Tg values of G 1-8COOH and P4VP were at 147 and 138°C, respectively.

Fluorous mixture synthesis of asymmetric dendrimers

A divergent fluorous mixture synthesis (FMS) of asymmetric fluorinated dendrimers has been developed. Four generations of fluorinated dendrimers with the same fluorinated moiety were prepared with high efficiency, yield, and purity. Comparison of the physicochemical properties of these dendrimers provided valuable information for their application and future optimization. This strategy has not only provided a practical method for the synthesis and purification of dendrimers, but also established the possibility of utilizing the same fluorinated moiety for FMS.