Fig. 5. X-ray structure of the reference compound 14 ("half of the tweezers"). The carboxyl groups are not separated by a spacer and form a dimer, as expected [14]. by hydrogen bondingThe 1 : f composition of the host-guest complexes of 12 and the high association constants suggest that the guest molecules are bound, as planned,[31 by hydrogen bonds in the noncollapsible molecular niche between the two functional groups. Remarkably, in earlier investigations of host compounds for nucleobases, for example tri-and bis(catechol) macrocycles,['Ob-dl the same order of bonding strengths was found for this type of guest.In conclusion, these tweezer molecules, the first constructed from cyclophanes, are strongly binding and selective hosts. The synthesis of other molecular tweezers of this type with various spacers, other functional groups, and with more than two convergent fixed functions appears to be worthwhile. Experimental Procedure 11:Compound 10 (121 mg, 0.35mmol) and copper(1) iodide (100mg, 0.52 mmol) were dissolved in degassed triethylamine (30 mL) under inert gas and heated at 80°C for 6 h. After the reaction mixture had cooled, the solvent was distilled off under vacuum and the residue purified by chromatography ( R , = 0.76; S O , , particle size 60-100 pm, dichloromethane/petroleum ether 40-60 (1 : 1)) to give colorless crystals (70 mg, 58%). 12/13. Compound 11 (69 mg, 0.1 mmol) was dissolved in anhydrous pyridine (30 mL). treated with anhydrous lithium iodide (403 mg, 3 mmol), and heated at reflux for 8 d. The solvent was distilled off under vacuum and the residue taken up in trichloromethane (20 mL) and 2~ HCI (20 mL) and extracted repeatedly with trichloromethane. The combined organic phases were washed three times with 6N HCI and dried over Na,SO,. The solvent was removed under vacuum and the residue purified by flashchromatography (SiO,, particle size 30-60 pm, trichloromethane/methanol (50: 1)). Fraction 1 (R, = 0.45): 36 mg (53%) monocarboxylic acid 13; fraction 2 ( R , = 0.22); 18 mg, biscarboxylic acid 12.
Experimentelles .In einem l00mL-Dreihalskolben, der mit Thermometer, Argon-EinlaB und Septum ausgestattet ist, werden 3.8 mL (13 mmol) Ti(OrPr), und 0.2 g (0.53 mmol) (1 R,2R)-1,2-Bis(trifluorsulfonamido)cyclohexan in 3 mL trockenem Toluol vorgelegt. Das Reaktionsgemisch wird auf 40-45 "C wihrend 0.5 h erwirmt und danach auf -60 ' C abgekuhlt. Bis(4-ch1orbutyl)zink (ca. 15 mmol; hergestellt aus 8.2 g (38 mmol) 1 -Chlor-4-iodbutan. 6.0 mL (59mmol) EtJn und einer katalytischen Menge (20mg. 0.11 mmol) CuI; 50°C. 16 h) (I] wurden in 16 mL trockenem Toluol gelost und LU der gekiihlten Reaktionslosung gegeben. Nach 5 inin wird der Aldehyd 5 b (1.96 g, 5.65 mmol) zugegeben. Das Reaktionsgemisch wird 16 h bei -35°C geruhrt (ca. 2 h hei -60°C im Fall von 6) und wie ublich aufgearbeitet. Dds entstandene 0 1 wird durch Flash-Chromatographie gereinigt (Hexan-Ether = 4: I ) und liefert den reinen Alkohol 8d als farbloses 01 (1.97 g, 79% Ausbeute; [NIP = -2.0 (c = 8.95, C,H,)). Im Falle des Aldehydes 6 wird nur ein UberschuB von zwei Aquivalenten [R'(CH,),],Zn benotigt. Eingegangen am 10. Dcaember 1992 [Z 57421 einem Uberschiin Me,SiCI behandelt. Man erhielt ndch wiBriger Aufarbeitung I-Trimethylsilyl-3-undecanol (79% Ausbeute, 93% ee; [N];' = -4.0 (c = 6.69, C,H,)).
structure structure (organic substances) K 9000 -040Structure and Symmetry of the Benzene Cation.-From its first photoelectron spectrum with fully resolved rotational lines it is concluded that the benzene cation is planar with D6h symmetry in the ground state. -(LINDNER, R.; SEKIYA, H.; BEYL, B.; MUELLER-DETHLEFS, K.; Angew.
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