Allyl propynyl ethers of general formula RCECCHZOCHZCH=CHR (1) undergo cycloremangement to 3-oxabicyclo[4.l.0lhept-4-enes (2) in oxygen-free benzene upon brief treatment a t room temperature with catalytic amount of PtC14. The transformation of 1 to 2 is assumed to involve platinumallene intermediates. The structure of 7-(l-naphthyl)-6-phenyl-3-oxabicyclo[4.l.0lhept-4-ene (2c) has been determined by X-ray diffraction analysis. The naphthyl and phenyl groups were shown to be oriented cis to each other. In the presence of [(CO2)Rh(~-C1)12 the oxabicycloheptenes 2 undergo cyclopropane-ring cleavage. 6,7-Diphenyl-3-oxabicyclo[4.l.0]hept-4-ene (2b) forms the rhodocyclic complex 3b. In the absence of air, the oxygen-free analog of la, PhC=C(CHz)&H=CHz (4), rearranges to the unstable 7-phenylbicyclo[3.2.Olhept-1(7)-ene (51, which can be trapped by oxygen as stable 2-(2-oxo-2-phenylethyl)cyclopentanone (6).
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