Photochemical Rearrangements of Organic Molecules

Thermal and photochemical rearrangements of bicyclic epoxides and ketones

“…The photochemical excitation of the carbonyl group of a simple cycloalkanone often leads to fission of the bond be tween the carbonyl group and the more heavily substituted o(-carbon (20). This "«T-cleavage" leads to the formation of un saturated aldehydes and/or saturated ketenes.…”

“…This "«T-cleavage" leads to the formation of un saturated aldehydes and/or saturated ketenes. Schematically> using cyclohexanone as an example, the oC-cleavage may be viewed as a homolytic fission to an intermediate (X\riII) which can undergo intramolecular abstraction of a hydrogen atom at the carbon adjacent to the alkyl radical giving the unsaturated aldehyde (XIX) or from the carbon adjacent to the acyl radical giving the ketene (XX) (20). Evidence to sup port the mechanism for both aldehyde formation (21) and ketene formation (22) has been reported.…”

Photochemistry of isocolchicine and related compounds

“…Irradiation of simple tropolones such as ^-tropolone methyl ether (VI) (13) and cK-tropolone methyl ethers (VIII a, b, and c) (14) gives good yields of bicyclic photoproducts VII and IX a, b, and c respectively. In direct contrast, ^ -tropolone methyl ether (X) (15) and tropone XII (16) give only complex mixtures of photoproducts . It has been shown by Schenck (ll) and Gardner (17) that colchiceine (XV) undergoes light-induced 1somerization and dimerization reactions analogous to those of colchicine.…”