A NOVEL PTCL4-CATALYZED CYCLOREARRANGEMENT OF ALLYL PROPYNYL ETHERS TO 3-OXABICYCLO[4.1.0]HEPTENES

Allyl propynyl ethers of general formula RC-CCH2OCH2CH=CHR' (1) undergo cyclorearrangement to 3-oxabicyclo[4.1.0]hept-4-enes (2) in oxygen-free benzene upon brief treatment at room temperature with catalytic amount of PtCl4. The transformation of 1 to 2 is assumed to involve platinum-allene intermediates. The structure of 7-(1-naphthyl)-6-phenyl-3-oxabicyclo[4.1.0]hept-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(mu-Cl)](2) the oxabicycloheptenes 2 undergo cyclopropane-ring cleavage. 6,7-Diphenyl-3-oxabicyclo[4.1.0lhept-4-ene (2b) forms the rhodocyclic complex 3b. In the absence of air, the oxygen-free analog of 1a, PhC=C(CH2)(3)CH=CH2 (4), rearranges to the unstable 7-phenylbicyclo[3.2.0]hept-1(7)-ene (5), which can be trapped by oxygen as stable 2-(2-oxo-2-phenylethyl)cyclopentanone (6).