132774-87-9Relevant academic research and scientific papers
Guest Capture during Shell Closure1a-c
Bryant, Judi A.,Blanda, Michael T.,Vincenti, Marco,Cram, Donald J.
, p. 2167 - 2172 (2007/10/02)
The preparation and properties of seven new carceplexes 1-7 of general structure H·G are reported in which H is an enforced closed-shell molecule (carcerand) composed of linked anisyl moities to which are attached pendant R groups required to impart solubility to the complexes. The guest molecules (G) are incarcerated in the enforced hollow interior of the hosts: 1, R = CH2CH2C6H5 and G = CH3OH·HOCH3; 2, R = CH2CH2C6H5 and G = CH3CN·NCCH3; 3, R = CH2CH2C6H5 and G = CH3CN; 4, R = (CH2)4CH3 and G = (CH3)2NCHO; 5, R = (CH2)4CH3 and G = CH3CH2OH; 6, R = (CH2)4CH3 and G = CH3COCH2CH3; and 7, R = (CH2)4CH3 and G = CH3CH2COCH2CH3. The complexes were all thermally stable except that H·CH3CN·NCCH3 when heated gave H·CH3CN plus CH3CN. The critical shell-closing reactions used to prepare 1-7 involved a 4-fold substitution in which four CH2Cl groups attached to the rim of a cavitand reacted with a second cavitand with four CH2SH groups attached to its rim. The M2CO3-catalyzed reactions were run in solvents whose molecules fitted well into the interiors of the carcerands on the basis of an inspection of Corey-Pauling-Koltun (CPK) molecular models. The nonpolar complexes were purified by chromatography. The yields were high for the 4-fold reactions: 1, 22%; 2 + 3 mixture, 25%; 4, 20%; 5, 20%; 6, 32%; and 7, 23%. No shell closure occurred with benzene as solvent. When conducted in benzene-alcohol or benzene-acetonitrile, only the more polar component was incarcerated. All carceplexes except 2 gave strong molecular ions in their desorption chemical ionization mass spectra (DCI MS) ((CH3)3CH was the reagent gas), in both their positive and negative ion modes. The proton signals of the guests in 1-7 occurred 1-4 ppm upfield in their 1H NMR spectra in CDCl3, while the chemical shifts of the inward-turned protons of the OCH2O groups of the hosts were guest-sensitive. The 1H NMR spectra of 1 and 3-5 indicated that the guests rotated about both the C2 and C4 axes of the host rapidly on the 1H NMR time scales (360 and 500 MHz). The spectrum of 6 indicates the long axis of the CH3COCH2CH3 guest is aligned with the C4 axis of the host and rotates around this axis rapidly, but not about the shorter C2 axes.
