Abstract
Flexible chain-like molecules can adopt various conformations, but fabrication of complex and higher-order architectures by chain networking or coiling is still a difficult task in organic chemistry. As the degree of freedom increases, the large entropy loss impedes conformation and orientation fixing. Here we report oligo (3,3-dimethylpentane-2,4-dione)s as flexible and shapable carbon chains with many carbonyl groups for chemical modification. Polycarbonylated chains of various lengths are synthesized by terminal-selective silylation and oxidative coupling reactions using silver(I) oxide. We use reactions of 1,3-diketones and 1,4-diketones to reduce the chain length and to induce favourable conformations. When the chains are treated with hydrazine, all the carbonyl groups are converted to imine groups, resulting in the formation of multidentate ligands. Finally, a two-dimensional sheet-like structure and a cylindrical assembly are generated by respectively networking and coiling the carbon chains, with the aid of metal coordination.
Highlights
Flexible chain-like molecules can adopt various conformations, but fabrication of complex and higher-order architectures by chain networking or coiling is still a difficult task in organic chemistry
Polyketone chains composed of alternating 1,3-diketone and 1,4-diketone subunits were prepared by enol silyl ether formation at the terminal carbonyl group and subsequent stepwise oxidative homo-coupling (Fig. 2)
We have achieved the synthesis, chain length modulation, conformation induction, and formation of assemblies of flexible carbon chains based on oligo(acetylacetone)s
Summary
Flexible chain-like molecules can adopt various conformations, but fabrication of complex and higher-order architectures by chain networking or coiling is still a difficult task in organic chemistry. Given recent developments in synthetic reactions using transition-metalcatalyzed functionalization of aliphatic compounds[9], the inducement of various conformations, and the construction of twoand three-dimensional assemblies with flexible carbon chains (Fig. 1a) become more important for synthesis of a new class of structurally flexible organic architectures with various size and shape. Natural polyketones, which consist of repeated 1,3-diketones, readily undergo intramolecular cyclization reactions through enolization to form stable six-membered rings, which often aromatize after dehydration (Fig. 1c)[11, 12].
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