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out in toluene are illustrative examples of this achievement.
Further studies towards the application of cationic ligands in
other contexts are currently underway in our research group.
Experimental Section
Synthesis of 5 f. A dried Schlenk flask was charged with 1,1’-(bi-
phenyl-2-yl)-phosphine (2.24 g, 12.0 mmol), chloro cyclopropenium
salt 2 (2.15 g, 6.0 mmol), and diglyme (20.0 mL), and the resulting
mixture was heated overnight at 1008C. After cooling of the reac-
tion mixture to room temperature, the solvent was removed in
vacuo, the residue dissolved in DCM, and the organic phase
washed with a saturated aqueous solution of NaBF4. Then, the or-
ganic phase was dried over sodium sulfate, and the solvent evap-
orated in vacuo to afford a residue that was finally purified by
column chromatography on silica gel (DCM/Acetone, 9:1). White
solid (1.86 g, 61%). 1H NMR (400 MHz, CDCl3): d=1.08 (d, J=
6.8 Hz, 6H), 1.16 (d, J=6.8 Hz, 6H), 1.34 (d, J=6.8 Hz, 6H), 1.37 (d,
J=6.8 Hz, 6H), 3.65 (septd, J=6.8, 1.8 Hz, 2H), 4.12 (sept, J=
6.9 Hz, 2H), 5.39 (d, J=233.3 Hz, 1H), 7.22–7.23 (m, 1H), 7.26 (m,
1H, overlaps with solvent signal) 7.31–7.51 (m, 6H), 7.69–7.75 ppm
(m, 1H); 13C{1H} NMR (101 MHz, CDCl3): d=21.0, 21.0, 21.5, 21.5,
Scheme 4. Synthesis of Calanhydroquinone A and Calanquinone C. Reagents
and conditions: a) 38 (1 equiv), 37 (1.5 equiv), Pd2(dba)3 (5 mol%), PCy3
(11 mol%), Cs2CO3, 1,4-dioxane/toluene, yield 84%. b) Ohira-Bestmann re-
agent (1.5 equiv), MeOH, K2CO3, yield 67%. c) 21(SbF6) (0.5 mol%), AgSbF6
(0.5 mol%), toluene, yield 89%. d) H2 (20 Bar), Pd/C (10 mol%), yield 89%.
e) (NH4)2Ce(NO3)6 (1 equiv), THF/H2O, yield 69%.
22.1, 22.2, 49.4, 56.5, 103.4 (d, JPꢀC =58.4 Hz), 124.9 (d, JPꢀC =
8.1 Hz), 128.2, 128.7, 128.9 (d, JPꢀC =4.4 Hz), 129.1 (d, JPꢀC =3.0 Hz),
130.6 (d, JPꢀC =4.0 Hz), 131.0, 136.8 (d, JPꢀC =9.3 Hz), 138.9 (d,
J
PꢀC =2.0 Hz), 141.0 (d, JPꢀC =4.0 Hz), 147.9 ppm (d, JPꢀC =20.2 Hz);
31P{1H} NMR (161 MHz, CDCl3): d=ꢀ78.0 ppm; IR (solid): n˜ =702,
762, 861, 884, 1029, 1152, 1340, 1458, 1562, 1874, 2297, 2984 cmꢀ1
;
HRMS (ESI): m/z calcd for C27H38N2P+: 421.276711 [MꢀBF4]+; found:
421.276383.
Synthesis of 1 f. Dry THF (5 mL) was added at ꢀ408C to a solid
mixture of KHMDS (325 mg, 1.63 mmol) and phosphine 5 f
(830 mg, 1.63 mmol), and the resulting suspension was stirred at
this temperature for 2 h. Then, the desired chloro cyclopropenium
salt (580 mg, 1.63 mmol) was added, and the reaction warmed to
room temperature overnight. Removal of the solvent in vacuo af-
forded a residue that was dissolved in DCM and washed with a sa-
turated solution of NaBF4 (3x). For a final purification, the obtained
1
residue was washed with THF. White solid (660 mg, 49%). H NMR
(400 MHz, CD3CN): d=0.97 (d, J=6.8 Hz, 12H), 1.16 (d, J=6.8 Hz,
12H), 1.32 (d, J=6.8 Hz, 12H), 1.35 (d, J=6.8 Hz, 12H), 3.68–3.71
(mbr, 4H), 4.13 (sept, J=6.8 Hz, 4H), 7.17–7.19 (m, 2H), 7.44–7.50
(m, 3H), 7.52–7.56 (m, 1H), 7.60–7.64 (m, 1H), 7.67–7.70 (m, 1H),
7.73 ppm (td, J=7.5 Hz, 1.3 Hz, 1H); 13C{1H} NMR (101 MHz,
CD3CN): d=21.1, 21.2, 21.5, 21.6, 21.6, 21.7, 53.2, 56.0, 98.7 (d,
J
PꢀC =60.6 Hz), 125.7, 129.7, 129.8, 129.9 (d, JPꢀC =4.0 Hz), 130.2,
132.4 (d, JPꢀC =6.5 Hz), 134.0, 136.2 (d, JPꢀC =3.1 Hz), 140.6 (d,
PꢀC =2.0 Hz), 140.7, 150.0 ppm (d,
PꢀC =36.1 Hz); 31P{1H} NMR
J
J
Figure 8. Molecular structures of compounds 42 (left) and 36 (right) in the
solid state. Anisotropic displacement parameters are shown at 50% proba-
bility level and hydrogen atoms not directly bonded to an oxygen are omit-
ted for clarity.[6]
(162 MHz, CD3CN): d=ꢀ54.7 ppm; IR (solid): n˜ =440, 519, 549, 578,
616, 640, 666, 688, 705, 740, 761, 891, 1028, 1048, 1150, 1182,
1204, 1283, 1353, 1376, 1457, 1552, 1852, 2879, 2939, 2976 cmꢀ1
;
HRMS (ESI): m/z calcd for C42H65BF4N4P+: 743.497053 [MꢀBF4]+;
found: 743.498110.
tho[2,1-b]furans. In this reaction, the strong Lewis acidity gen-
erated at the AuI center probably makes the final release of
the product rate determining; hence, the bulky biaryl substitu- Acknowledgements
ent is essential for a faster transformation. On the other hand,
the introduction of long chain dialkylamino substituents to the
ligand structure increases the solubility of the resulting cata-
lysts and, consequently, chlorinated solvents are not necessary
as reaction medium. The syntheses of Calanquinone C and Cal-
anhydroquinone A through a key hydroarylation step carried
The X-ray structural determination of 36 was carried out at the
light source PETRA III at DESY, a member of the Helmholtz As-
sociation (HGF). We would like to thank A. Burkhardt and S.
Panneerselvam for assistance in using the beamline P11. We
also acknowledge the NMR spectroscopy and X-ray crystallog-
Chem. Eur. J. 2016, 22, 1 – 9
7
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