The photoirradiation of 3,5-disubstituted 2-isoxazolines and Fe(CO)5 in MeOH causes the N–O and C4–C5 bond cleavage to give two fragments of aldehydes and ketones, while that of 2-isoxazolines having no substituent at 5-position gives additional β-hydroxy- and β-methoxyketones.
1,5-Dimethyl-6-oxacyclopropylidenetricyclo[3.2.1.02,7] oct-3-en-8-one (II), upon irradiation, afforded 4,8-dimethyl-1,4-dihydrobenzopyran-3-one (III). This rearrangement was considered to be a novel ene-type reaction of photochemically generated ketene with the moiety involving an epoxide ring. The ketene intermediate was detected by low temperature ir spectrum as well.
Ultraviolet irradiation of 6-methylenetricyclo[3.2.1.02,7]oct-3-en-8-ols (Ia) and (Ib) afforded 3-methylenetetracyclo[3.3.0.0.4,602,8]octan-7-ols (IIa) and (IIb) in fairly good yields. This photorearrangement is considered to be a di-π-methane rearrangement. Oxidation of the photoproducts gave the ketones retaining the carbon skeleton of IIa and IIb
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