Fulleropyrrolidines derived from dioxa- and trioxaalkyl-tethered diglycines

Abstract

Two different a,u-diglicynes linked by linear polyoxaalkyl chains in the presence of formaldehyde underwent Prato reaction to the fullerene C 60 . The shorter linker templated formation of only cisbisadducts, while the longer one afforded a mixture of four bisadducts (all cis and the equatorial) and difullerene dumbbell compound. Their structures were confirmed by the extensive analysis of the spectral data and molecular symmetry, as well. All compounds expressed an ability to arrange into hierarchically ordered supramolecular aggregates, the form of which depended both on the addition pattern and the spacer structure. The attenuated electron-accepting affinity, examined by cyclic voltammetry was in agreement with diminished delocalization of the p-electronic system. In addition, all compounds exerted a notable radical scavenging activity. † Electronic supplementary information (ESI) available: Experimental section, tabular representation of the UV and the NMR data, the NMR and HRMS spectra, additional SEM images, the CV curves of compounds 3-14, and their HPTLC densitograms. See

Fullerene bisadduct regioisomers containing an asymmetric diamide tether

“…The relative ratio of the isolated regioisomeric bisadducts e-edge/e-face/trans-4/cis-2 was 1.0:1.9:1.5:4.9. Comparative analysis of the ratio of the obtained bisadduct regioisomers 17 with those in recently synthesized bisadducts in two series with flexible tethers of a similar length (dodecamethylene 12 and trioxatridecamethylene-tethered substrates 13 ) revealed a dependence of the regioselectivity on the tether structure. Table 1 illustrates a comparison of their regioselectivity with various distribution of cis-, equatorial and trans-4 regioisomers and better regioselectivity of the investigated cycloaddition reaction relative to bisadducts prepared using Prato biscycloaddition with a polyoxa-tethered bisglycine derivative.…”

“…UV spectra were recorded with a GBC-Cintra 40 UV-vis spectrophotometer. 1 H-and 13 C NMR spectra were recorded with Varian Gemini 200 ( 1 H at 200 MHz, 13 C at 50 MHz) and Bruker Avance spectrometers ( 1 H at 500 MHz, 13 C at 125 MHz). Chemical shifts are measured in ppm, J in Hz.…”

“…The sample was dissolved in the indicated solvent system, and TMS was used as an internal reference. The homonuclear 2D (DQF-COSY) and the heteronuclear 2D 1 H- 13 C spectra (HSQC, HMBC) were recorded with the usual settings. The NMR spectra of all carbamates (4−7, 11 and 12) are consistent with the expected structure but are complicated (splitting of some signals) by the presence of carbamate rotamers.…”

“…Tetrahedron 2 phenyl-C 61 -butyric acid methyl ester using a tether-directed 1,3dipolar cycloaddition of azomethine ylides was reported by Zhang and co-workers. 8 The selectivity of a double Prato cycloaddition of C 2νsymmetric diglycine substrates as reactive centers linked by flexible alkyl 12 or polyoxamethylene 13 tethers to the fullerene C 60 was recently examined in our research group. The results showed that the regioselectivity of a one-pot biscycloaddition of the investigated flexible substrates on fullerene is significantly improved, giving mostly mixtures of cis-regioisomers with the exception of dodecamethylene-and trioxatridecamethylenetethers which additionally give trans-4 and/or equatorial isomers.…”

“…The addition patterns were confirmed by comparison with the UV/Vis absorption spectra of previously reported bispyrrolidinofullerenes bridged by flexible alkyl-and polyoxamethylene-tethers. 12,13 According to the number of 13 C signals and their intensities, the isomers 17a and 17b are symmetric, matching the Cs-symmetry of the equatorial bisaddition patterns, e-edge and e-face, respectively, while the regioisomers 17c and 17d are asymmetric. The 13 C NMR spectra of the two equatorial isomers showed 29 fullerene sp 2 resonances, two of which have half-intensity, indicating their Cs symmetry (SI, Figures S63 and S71).…”