Organic Lab Reactions 124

Organic Lab Reactions 124 - cyclized under the mildest...

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ORTHO AND PARA DIRECTING GROUPS 119 intramolecular reaction. Thus as ortho and para directing groups enhance intermolecular acylation, so ring closures are preferably directed to one of these positions rather than into an unsubstituted nucleus. This has been substantiated 13 in the ring closure of /3-m-tolylhydrocin- namic acid (XIX). The product of reaction, obtained in 60% yield, consisted solely of 5-methyl-3-phenylhydrindone-l (XX), arising from acylation para to the methyl group. No material was found which cor- responded to cyclization into the unsubstituted nucleus. A similar result was observed in the ring closure of a-benzyl-/S-»»-tolylpropionic acid (XXI). The hydrindone XXII, formed in 75% yield by substitu- tion at the para position to the methyl group, was the only ketone encountered. CO 2 H 0 C,H 6 XXI XXII The powerful activating influence of the methoxyl group is indicated by the fact that 7-m-methoxyphenylbutyric acid (LIII, p. 125) can be
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Unformatted text preview: cyclized under the mildest conditions in 96% yield. 14 In the cyclization of 7-5-methoxy-l-naphthylbutyric acid (formula XCIV, p. 175), the course of the ring closure seemed to depend somewhat upon the reagent and conditions of the reaction, but the formation of the seven-membered ring ketone XCIII was definitely favored over the production of the phenanthrene derivative XCV. The activating influence of the methoxyl group, therefore, seemed to offset in part the preference for the forma-tion of a six-membered ring. Cyclizations meta to an ortho, para directing substituent are known. For example, the 7-substituted tetralones XXIV were prepared 16 from the corresponding arylbutyric acids XXIII. 13 v. Braun, Manz, and Reinsch, Ann., 468, 277 (1929). 14 Bachmann and Thomas, J. Am. Chem. Soc., 64, 94 (1942). " Krollpfeiffer and Sch&fer, Ber., 56, 620 (1923)....
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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.

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