Stereoselective Arene‐Forming Aldol Condensation: Synthesis of Configurationally Stable Oligo‐1,2‐naphthylenes

Abstract

Structurally well-defined oligomers are fundamental for the functionality of natural molecular systems and key for the design of synthetic counterparts. Herein, we describe a strategy for the efficient synthesis of individual stereoisomers of 1,2-naphthylene oligomers by iterative building block additions and consecutive stereoselective arene-forming aldol condensation reactions. The catalyst-controlled atropoenantioselective and the substrate-controlled atropodiastereoselective aldol condensation reaction provide structurally distinct ter- and quaternaphthalene stereoisomers, which represent configurationally stable analogues of otherwise stereodynamic, helically shaped ortho-phenylenes.

Charge Transfer Pathways in Three Isomers of Naphthalene-Bridged Organic Mixed Valence Compounds

“…1 Naphthalene-based structures as molecular bridges for longrange charge transfer are much less well explored, 2 but recently developed new synthetic methods make such structures much more amenable. 3 Depending on the naphthalene substitution pattern significant differences in charge transfer properties have been reported, 4 in analogy to what was found when comparing ortho-, meta-, and para-substituted phenylenes. 5 Several recent studies have attempted to identify orbital rules for charge transfer and charge transport in naphthalenes and related aromatic molecules.…”

Enantioselective Synthesis of Atropisomers with Multiple Stereogenic Axes

“…[27] In 2016, Sparr and coworkers developed ac ompelling and efficient enantioselective aldol condensation for the construction of oligo-1,2naphthylenes with one stereogenic axis (Scheme 13). [28] The natural amino acid l-isoleucine catalyzed the stereoselective intramolecular aldol addition of the in situ double-oxidation product of 35,a nd the conversion of the central chirality to the axial chirality during the dehydrative arene-forming process afforded the oligoarene 36 in 71 %y ield and 90 % ee. To generate the second axis,amixed-metal species 37,the building block for the preparation of 35,w as added to build as imilar aldol addition precursor unit 38.T hus,t he in situ double-oxidation and the substrate-controlled diastereoselective arene-forming aldol condensation sequence formed the atropisomers 39 featuring two stereogenic axes with 1,2arrangement and as econdary P-helix substructure in 29 % yield and 79:21 dr.…”

Stereoselective arene formation

“…In this context, our group studied a strategy to access individual stereoisomers of 1,2-naphthylene oligomers (Scheme 25). 46 Iterative addition of an organometallic building block and consecutive catalyst-or respectively substrate-controlled stereoselective areneforming aldol condensation gave access to structurally well-defined oligo-1,2-naphthylene stereoisomers. Intriguingly, for the configurationally stable stereoisomer with a secondary helical structure, a racemisation barrier of 154 kJ mol -1 was measured.…”