| Abstract
| - The novel lactonizations of methyl 4-aryl-5-tosyloxypentanoate 1 and 4-aryl-5-tosyloxyhexanoate3 concomitant with a phenyl rearrangement are reported. The lactonizations were promoted bysilica gel or heating in various solvents. By examining the effects of substituents of the aromaticring on the reactivity, it was found that the reaction proceeded via a phenonium ion. This findingwas supported by the stereochemical results for the lactonization of optical active 1. Silica gel-promoted lactonization of 1 gave only γ-lactone 2, whereas that of 3 afforded γ-lactone 4 andδ-lactone 5. These lactonizations proved to be kinetically controlled. On the other hand, when 3cwas heated in CH3NO2 at 70 °C, the highly selective formation of 4c was observed. Further detailedexperiments confirmed that the thermal lactonization in CH3NO2 was thermodynamically controlled.
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