2-Alkenyl-2-oxazoline-5-ones

The photochemistry of more complex and highly substituted alkenic partners has been studied. In 1978, Hartmann and coworkers reported the photocycloaddition of 4-oxazolin-2-one with acetone, used as a photosensitizer in the reaction of 4-oxazolin-2-one with alkenyl and alkynyl partners, to form oxe-tane (44). Recently, Scharf has described the photochemistry of 3-acetyl-2,3-dihydio-2,2-dimcthyloxa-zole (45). Irradiation of (45) in the presence of acetophenone produced the oxetane (46) with the phenyl group endo (17%), in addition to 21% of a ring-opened derivative. The stereoselectivity is in agreement with the high exo carboxyl selectivity observed in the photocycloaddition of methyl phe-nylglyoxylate with 2,2-dimethyl-1,3-dioxole to produce oxetane (47). 

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