The concept of "frustrated Lewis pairs" involves donor and acceptor sites in which steric congestion precludes Lewis acid-base adduct formation. In the case of sterically demanding phosphines and boranes, this lack of self-quenching prompts nucleophilic attack at a carbon para to B followed by fluoride transfer affording zwitterionic phosphonium borates [R(3)P(C(6)F(4))BF(C(6)F(5))(2)] and [R(2)PH(C(6)F(4))BF(C(6)F(5))(2)]. These can be easily transformed into the cationic phosphonium-boranes [R(3)P(C(6)F(4))B(C(6)F(5))(2)](+) and [R(2)PH(C(6)F(4))B(C(6)F(5))(2)](+) or into the neutral phosphino-boranes R(2)P(C(6)F(4))B(C(6)F(5))(2).
View Article and Find Full Text PDFThis manuscript describes the successful synthesis and characterization of five generations of dendrimers based on melamine. Early generations of these materials appear to be single chemical entities: upon purification, no detectable impurities are observed using NMR spectroscopy, mass spectrometry, and HPLC and GPC analysis. The analysis of larger generation materials precludes an unambiguous statement of purity.
View Article and Find Full Text PDFA comprehensive and chronological account of dendrimers based on [1,3,5]-triazines is provided. Synthetic strategies to install the triazine through cycloaddition, cyclotrimerization, and nucleophilic aromatic substitution of cyanuric chloride are discussed. Motivations and applications of these architectures are surveyed, including the preparation of supra-molecular assemblies in the solution and solid states and their use in medicines, advanced materials, and separations when anchored to solid supports.
View Article and Find Full Text PDF[reaction: see text] A synthetic route for obtaining functional group diversity in macromolecules is described. The route relies on the differential reactivity of substituted dichlorotriazines. Treatment of a triamine core with substituted dichlorotriazines cleanly yields tris(monochlorotriazines).
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