An enantioconvergent Friedel-Crafts alkylation of indoles with donor-acceptor cyclopropanes is described. The reaction is catalyzed by pybox•MgI2 and proceeds via a type I dynamic kinetic asymmetric transformation (DyKAT).
Aminobenzaldehydes bearing a pendant 3,5-dinitrophenyl group react thermally with N-substituted α-amino acids to form unprecedented benzoazepine-fused isoindolines. The reaction proceeds via a dearomatization/ rearomatization sequence involving an intramolecular (3 + 2)-cycloaddition between the in situ formed azomethine ylide and the dinitroarene. Various glycine derivatives are tolerated as well as branched substrates based on cyclic, α-mono-, and α,α-disubstituted amino acids, giving single diastereomers in many cases. The method is scalable and gives products with a nitro group ready for further manipulation.
Summary
Communication of information through the global switching of conformation in synthetic molecules has hitherto entailed the inversion of chirality. Here, we report a class of oligomer through which information may be communicated through a global reversal of polarity. Ethylene-bridged oligoureas are constitutionally symmetrical, conformationally flexible molecules organized by a single chain of hydrogen bonds running the full length of the oligomer. NMR reveals that this hydrogen-bonded chain may undergo a coherent reversal of directionality. The directional uniformity of the hydrogen-bond chain allows it to act as a channel for the spatial communication of information on a molecular scale. A binding site at the terminus of an oligomer detects local information about changes in pH or anion concentration and transmits that information—in the form of a directionality switch in the hydrogen-bond chain—to a remote polarity-sensitive fluorophore. This propagation of polarity-encoded information provides a new mechanism for molecular communication.
The chiral pool-derived 1,1'-ditosyl-2,2'-biaziridine has been established as a valuable building block for the divergent synthesis of enantiopure vicinal diamines. Efficient procedures for the regioselective ring opening of the biaziridine with oxygen, sulfur, nitrogen, and carbon nucleophiles are described. The strategic use of nucleophiles bearing pendant functionality allows further elaboration of the acyclic products to a variety of 2,2'-bicyclic-embedded diamines. Desymmetrization of the biaziridine has also been accomplished via the selective monoaddition of organocuprates.
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