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[摘要]：The synthesis of three- and four-layered [3.3]paracyclophanes ([3.3]PCPs) has been accomplished by utilizing the (p-ethylbenzenesulfonyl)methyl isocyanide (EbsMIC) method. The structures of the three- to four-layered [3.3]PCPs and their diones have been elucidated based on the 1H NMR spectra and finally by X-ray structural anal. In the three-layered [3.3]PCP-dione I (X = CO), the trimethylene bridges of the [3.3]PCP unit assume a chair conformation , while the [3.3]PCP-2,11-dione unit assumes a boat conformation different from that of [3.3]PCP-dione with a chair conformation. On the other hand, the two [3.3]PCP units in three-layered [3.3]PCP I (X = CH2) both assume a boat conformation. In the four-layered [3.3]PCP-dione II (X = CO), the two outer [3.3]PCP units assume a boat conformation while the inner dione unit has a chair conformation. The trimethylene bridges in the four-layered [3.3]PCP II (X = CH2) are highly disordered even at -150 癈. All the outer benzene rings are distorted into a boat form while the inner ones are distorted into a twist form. In the electronic spectra, bathochromic shift and hyperchromic effect are obsd., but the magnitude decreases with an increase in the no. of layers and the spectra become structureless. In the charge-transfer (CT) bands of the three- to four-layered [3.3]PCPs with tetracyanoethylene (TCNE), two absorption maxima (lmax) are obsd. The effect of an increase in the layers becomes significant, and the changes in the longest wavelength lmax values from two to three and three to four are ca. 60 and 50 nm, resp. By comparison of the stereoisomeric four-layered [3.3]PCPs II (X = CH2) (meso) and III (racemic), the helical arrangement of the trimethylene bridges of III shows a more efficient transannular p-electronic interaction. In the three- to four-layered [3.3]PCP-diones, a magnitude of the CT interaction almost comparable to that of [3.3]PCP was obsd., and this indicates that the -CH2COCH2- bridges inhibit the CT interaction and that this tendency is supported by the calcd. HOMO energy levels and obsd. oxidn. potentials. Three- and four-layered [3.3]PCPs show reversible redox processes, and II (X = CH2) and III show an electron-donating ability almost comparable to that of [36]CP. Very good correlation between the lmax of the CT bands with TCNE and the oxidn. potentials is obsd. |
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