Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

• Axel G. Griesbeck,
• Marco Franke,
• Jörg Neudörfl and
• Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

• -controlled formation of the corresponding triplet 1,4-biradical and high stereocontrol due to SOC-controlled crossing from the triplet to the singlet surface [4][5]. Reaction behavior of the photoproducts 9a–c All bicyclic oxetanes obtained in the analytical photochemical experiments as well as in

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

• according to the mechanism shown in Scheme 1 through biradical intermediates BR1 and BR2 and leads to the formation of the corresponding dibenzosemibullvalene (DBS) [6][7]. Notably, the photoreactivity of the dibenzobarrelene system is multiplicity-dependent: Upon photoinduced triplet sensitization in the

Synthesis of spiropyrans: H-abstractions in 3-cycloalkenyloxybenzopyrans

• Satish C. Gupta,
• Mandeep Thakur,
• Somesh Sharma,
• Urmila Berar,
• Surinder Berar and
• Ramesh C. Kamboj

Beilstein J. Org. Chem. 2007, 3, No. 14, doi:10.1186/1860-5397-3-14

• can be visualized as having occurred through an initial abstraction of the O-methine proton of cycloalkenyl group by the excited carbonyl of the pyrone moiety to produce 1,4-biradical 8. The photoproduct 5 (a, b, c, d), is then formed through bond formation between the alkoxy radical and furan (8