Abstract
We recently reported that chlorine substituents on the alkene control the regio selectivity of the cyclization of 5-hexenyl and 6-heptenyl radicals generated by oxidation of an acetoacetate ester or 1,3-diketone with Mn- (0Ac)3*2H20.1 One-electronoxidationofbenzoylacetone derivative 3a, containing a chlorine on the terminal double- bond carbon, gives -chloro radical 4a that adds to the aromatic ring to give 5a after a second one-electron oxidation. Loss of hydrogen chloride leads to naphthol 6a in 79% yield. The chlorine substituent plays two crucial roles in the conversion of 3a to 6a. Steric effects from the chlorine slow down the 7-endo cyclization thereby favoring the6-exocyclizationtogive4a. Notricyclicproductsare obtained from the deschloro analogue of 3a. Secondly, spontaneous loss of hydrogen chloride from 5a leads directly to the desired naphthol 6a.