The intermolecular [2+2] cycloaddition of allenol esters, which were in situ generated by Pt-catalyzed 1,3-acyloxy migration of propargylic esters, with C proceeded regio- and stereo-selectively to give a novel class of alkylidenecyclobutane-annulated fullerenes. The cyclobutane-annulated fullerene derivatives have high-lying LUMO levels, which gave a high open-circuit voltage in organic solar cell applications. The observed high electron mobility provided a good fill factor compared with the PCBM-based devices.
The reaction of 1,2‐diaryl‐1,2‐diketones, propiolic acid esters, and C60 in the presence of Et3N gave cyclopentene‐annulated fullerenes through a [3+2] cycloaddition. They were formed in two Et3N‐promoted steps, namely, the generation of 1,3‐bifunctional allenes and the cycloaddition of 1,3‐bifunctional allenes with C60. Interestingly, when a similar reaction was conducted using a flow packed‐bed reactor in combination with a silica‐supported tertiary amine, cyclobutane‐annulated fullerenes were obtained through a [2+2] cycloaddition.
The [2+2] cycloaddition of 3-alkoxycoumarins with C60 proceeded stereoselectively under photoirradiation conditions to produce a new class of fullerene fused oligocyclic cyclobutane products. This reaction seems to progress via radical ion pair intermediates that arise from the SET processing of 3-alkoxycoumarins with the excited form of C60.
The Front Cover shows the cycloaddition of C60 with benzyl and methyl propiolate in the presence of Et3N or silica‐supported tertiary amine. In our reaction system, Et3N‐catalyzed [3+2] cycloaddition of C60 gave cyclopentene‐annulated fullerene. On the other hand, cyclobutane‐annulated fullerene were obtained via [2+2] cycloaddition of C60 by using a flow packed‐bed reactor in combination with a silica‐supported tertiary amine. More information can be found in the Communication by M. Ueda et al.
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