Rhodium‐Catalyzed Highly Diastereo‐ and Enantioselective Synthesis of a Configurationally Stable S‐Shaped Double Helicene‐Like Molecule

Abstract

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Synthesis, Structure, and Complexation of an S‐Shaped Double Azahelicene with Inner‐Edge Nitrogen Atoms

“…The UV-vis spectrumo fdl-1 in CHCl 3 solution showed a broad absorption with maximaa t4 67 (e,4 470), 442 (3450), and 281 (54100) nm (Figure 3a). The shape of the spectrum of 1 is comparable to that of 1-aza [6]helicene 14, [13] albeit that the absorption maxima of 1 are redshifted (14;2 59, 399, 409 nm) duet ot he extended p-conjugation.T he longest wavelength absorption was assigned to the HOMO-LUMO transition (l calc = 494.6 nm; f = 0.119) based on time-dependent (TD) DFT calculations (TableS11). The HOMO (À4.62 eV) is mainly localizedo nt he central naphthalene moiety,w hile the LUMO (À1.53 eV) is delocalized over the entire molecule (Figure 4).…”

“…Meso-1 contains ac entero fs ymmetry at the midpoint of the C5ÀC5* bond. The dihedral angles of the terminal 1-aza [6]helicene moieties( rings A/F and E/J)a re 40.08 and 45.58 for rac-dl-1 and 51.28 for meso-1.T he inner C-C-C-C dihedral angles of rings B/D and C/E also differed between rac-dl-1 (20.6(3)-28. 8(3)8)a nd meso-1 (27.5(3)-32.0(3)8).…”

“…Subsequently,w ea ttempted to use benzoquinoline substrate 5 to synthesize [6]azahelicene with al arger helical structure (Scheme 2). However,l ess-hindered p-extended1 -aza [5]helicene 6 was obtained as the sole product, as the sterically less hindered 3-position participated in the reaction rather than the desired 1-position.M eanwhile, the reaction of substrates 7 with an additional substituent at the 3-position furnished [ 6]azahelicene 8 in excellenty ield.…”

“…8(3)8)a nd meso-1 (27.5(3)-32.0(3)8). Based on theoretical results for hypothetical molecules in which the aryl rings in 1 were sequentially removed from the terminal (Table S10), the difference in stability between rac-dl-1 and meso-1 was attributedp redominantly to the deformation of ring D.T he dihedral angles of the terminal 1-aza [6]helicene of 1 are smaller than those of (M)-1-aza [6]helicene [(M)-14] [12] (56.38)a nd the dl form of the analogousa ll-carbon-based double [6]helicene, dl-15, [6e] (47.78)( Ta ble S2).…”

“…Previously,a nS -shaped doublea zahelicene with nitrogen atomsembedded on its outer peripherale dge was synthesized by Ta naka; [5] however,t he inner-edge structure shown in Figure1has notb een reported yet. [6] Herein, we wish to report the first synthesis of S-shaped double azahelicene with two inner-edge nitrogen atoms and its trans-chelating bidentate coordination to palladium(II). To achievet his goal, we investigated the intramolecular dehydrogenative double CÀHf unctionalization of benzo[h]quinoline as ad irecting group (Scheme 1).…”