TY - JOUR
T1 - Synthesis, stereochemical characteristics, and coordination behavior of 2,2'-binaphthyl-1,1'-biisoquinoline as a new axially chiral bidentate ligand
AU - Kawatsu, Takahiro
AU - Tokushima, Hiroki
AU - Takedomi, Yuya
AU - Imahori, Tatsushi
AU - Igawa, Kazunobu
AU - Tomooka, Katsuhiko
AU - Irie, Ryo
N1 - Publisher Copyright:
©ARKAT-USA, Inc.
PY - 2015/7/6
Y1 - 2015/7/6
N2 - We describe the synthesis, stereochemical characteristics, and coordination behavior of 2,2'-binaphtyl-1,1'-biisoquinoline (BINIQ), a new axially chiral bidentate ligand. BINIQ was obtained in a racemic form by the diastereoselective Ullmann coupling of 1-(2-iodonaphthalen-1-yl)isoquinoline, which was prepared by the regioselective C-H iodination of 1-(1-naphthyl)isoquinoline. BINIQ has three chiral biaryl axes α and γ at the two naphthylisoquinoline and β at the 2,2'-binaphthyl sites and their relative configuration (αRaβRa , γa ) in solid state was confirmed by X-ray diffraction analysis. The naphthyl-isoquinoline axes α and γ were proven rigid enough in solution to allow for optical resolution by a chiral HPLC method and a solution of the optically pure BINIQ (98% ee) in chloroform-d did not result in racemization while standing at room temperature for 24 h. On the other hand, the 2,2'-binaphthyl axis is stereochemically labile and readily alternates between βRa and βSa at room temperature. Accordingly, (αRa a γa )- and (αRa a ,γRa)-BINIQ are in equilibrium in solution with the former stereoisomer being dominant, though the latter is suitable as a bidentate ligand. Notably, this dynamic stereochemical behavior enabled BINIQ to readily give the relative configuration (αRa a ,γRa ) upon coordination to a copper(I) ion at room temperature.
AB - We describe the synthesis, stereochemical characteristics, and coordination behavior of 2,2'-binaphtyl-1,1'-biisoquinoline (BINIQ), a new axially chiral bidentate ligand. BINIQ was obtained in a racemic form by the diastereoselective Ullmann coupling of 1-(2-iodonaphthalen-1-yl)isoquinoline, which was prepared by the regioselective C-H iodination of 1-(1-naphthyl)isoquinoline. BINIQ has three chiral biaryl axes α and γ at the two naphthylisoquinoline and β at the 2,2'-binaphthyl sites and their relative configuration (αRaβRa , γa ) in solid state was confirmed by X-ray diffraction analysis. The naphthyl-isoquinoline axes α and γ were proven rigid enough in solution to allow for optical resolution by a chiral HPLC method and a solution of the optically pure BINIQ (98% ee) in chloroform-d did not result in racemization while standing at room temperature for 24 h. On the other hand, the 2,2'-binaphthyl axis is stereochemically labile and readily alternates between βRa and βSa at room temperature. Accordingly, (αRa a γa )- and (αRa a ,γRa)-BINIQ are in equilibrium in solution with the former stereoisomer being dominant, though the latter is suitable as a bidentate ligand. Notably, this dynamic stereochemical behavior enabled BINIQ to readily give the relative configuration (αRa a ,γRa ) upon coordination to a copper(I) ion at room temperature.
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U2 - 10.3998/ark.5550190.p009.069
DO - 10.3998/ark.5550190.p009.069
M3 - Article
AN - SCOPUS:84938362495
VL - 2015
SP - 161
EP - 175
JO - Arkivoc
JF - Arkivoc
SN - 1424-6376
IS - 4
ER -