176 THE FORMATION OF CYCLIC KETONES as the only product isolated. The stannic chloride method upon repeti-tion m proved to be unreliable as it gave the phenanthrene derivative less frequently than the product of pen ring closure. The phosphorus pentoxide cyclization was shown also to give the aeven-membered ring closure. 24- »» A striking example of selective orientation is illustrated by the cyclization of 7-2-phenanthrylbutyric acid (XCVI). By the hydrogen0 (CH 2 ) 3 COaH xovi xovn fluoride method, a high yield pf ketone resulted consisting almost entirely of 8-keto-5,6,7,8-tetrahydro-l,2,-benzanthracene (XCVII), which was obtained pure in 78% yield. 43 In contrast, the pure isomeric 4-keto-l,2,3,4-tetrahydrochrysene (XCVTII), was obtained in 74% yield by the Friedel-Crafts stannic chloride method, 107 and in 51% yield by the zinc chloride acetic acid-anhydride technique. 43 When the ring was closed with sulfuric acid a mixture resulted from which only the chrysene derivative (XCVIII) could be isolated, and this in poor yield. An apparent influence of the solvent was noted in the action of alu-
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This note was uploaded on 11/20/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.