Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• formation of the dibenzosemibullvalene with moderate stereoselectivity (68:32 er). In contrast, the thioureido derivative showed no such effect upon complexation of chiral anions. Keywords: dibenzobarrelenes; dibenzosemibullvalenes; di-π-methane rearrangement; supramolecular photochemistry; (thio)urea

• two enantiomeric dibenzosemibullvalenes 2b and ent-2b. As indicated in Scheme 1, the two enantiomers originate from different vinyl–benzo bridging pathways in the first reaction step (path a or b). Note that the same two enantiomers are formed upon initial vinyl–benzo bridging with the other benzene

• : 4.76 ppm, in acetone). The dibenzosemibullvalene 2i was obtained in 52% yield by filtration through a column of silica gel and subsequent crystallization. The dibenzosemibullvalenes 2h and 2i were identified and fully characterized by 1H NMR and 13C NMR spectroscopy, elemental analysis and/or mass

Synthesis of cationic dibenzosemibullvalene-based phase-transfer catalysts by di-π-methane rearrangements of pyrrolinium-annelated dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 119–126, doi:10.3762/bjoc.7.17

• pyrrolidinium-annelated dibenzosemibullvalene may act as phase-transfer catalyst in alkylation reactions. Keywords: di-π-methane rearrangement; dibenzobarrelenes; dibenzosemibullvalenes; phase-transfer catalysis; photochemistry; polycylic compounds; Introduction The di-π-methane (DPM) rearrangement is among

• of the semibullvalene structure to enable additional hydrogen bonding with the substrate. Also, the benzene rings may be further annelated with additional aromatic units to increase the potential π-stacking area [13]. Most notably, dibenzosemibullvalenes are chiral compounds, so that the propensity

• of 2g. Thus, irradiation of 2g in acetonitrile for 12 h led to ca. 10% conversion with ca. 60% dibenzosemibullvalenes formed. At the same time, several unidentified byproducts were formed in significant amounts. The analysis of the photolysate by 1H NMR spectroscopy revealed that independent of the