Clive S. Penkett

The double [3+2] photocycloaddition reaction

A remarkable double [3 + 2] photocycloaddition reaction that results in the formation of fenestrane 2 from aromatic acetal 1 is reported. During the formation of 2, four carbon-carbon bonds, five new rings, and seven new stereocenters are created in a one-pot process. The reaction occurs in a sequential manner from the linear meta photocycloadduct 3, while the angular meta photocycloadduct 4 undergoes an alternative fragmentation-translocation photoreaction to afford angular tricycle 6.

Photosolvolysis reactions of 3-alkoxypyridinium tetrafluoroborate salts

Irradiation of a series of 3-alkoxypyridinium tetrafluoroborate salts in alcohol solution resulted in the formation of cyclopentenone ketals by diastereoselective incorporation of the alcohol solvent under the basic conditions of the photolysis reaction. In a second series of photochemical reactions, the same 3-alkoxypyridinium salts were irradiated in water to yield β-hydroxycyclopentanones stereoselectively.

Oxidative rearrangements of bicyclic 2-alkenyl aziridines

Oxidation of a range of photochemically generated aziridines gave products arising from a [2,3] Meisenheimer rearrangement of the initial N-oxide, followed by further oxidation to give delta-hydroxynitrones.

Investigating the photochemical properties of an arenyl dienol.

Upon irradiation with UV light, an arenyl dienol was transformed into linear and angular meta photocycloadducts and ortho derived photoadducts. Extended exposure to UV radiation resulted in the formation of other degradation products, which shed light on the chemical processes taking place. One of the linear meta photocycloadducts was thermally unstable and underwent further thermal and photochemical transformation, while the ortho-derived photocycloadducts ring-opened and eliminated methanol to afford a cyclooctadienone product.

Palladium catalyzed arylation reactions of meta photocycloadducts

We describe the first application of a Heck arylation reaction being performed on a meta photocycloadduct. The resulting arylation/fragmentation process leads to the formation of a bridged bicyclic ketone and constitutes a dramatic increase in molecular complexity after just two synthetic operations.