Organic Lab Reactions 127

Organic Lab Reactions 127 - found. STERIC FACTORS OTHER...

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122 THE FORMATION OF CYCLIC KETONES Examples of intramolecular acylation ortho to a carbonyl group are well known in the cyclization of o-benzoylbennoic acids to anthraquinones. It is noteworthy that this type of ring closure requires more drastic cyclizing conditions than are necessary for the usual type of intra- molecular acylation. Polycyclic Nuclei. In general, arylpropionic and arylbutyric acids in which the aryl group is a polycyclic aromatic nucleus cyclize readily. Cyclization into the a-position of the naphthalene nucleus, for example, takes place more easily than into the benzene ring. The ring closure of the substituted naphthylpropionic acids XXXIII and XXXV proceeded smoothly. YTYTTT XXXIV CH 2 C 6 H 8 XXXV The products, formed in yields above 70%, were the benzhydrindones XXXIV and XXXVI, respectively. 13 None of the isomeric ketones was
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Unformatted text preview: found. STERIC FACTORS OTHER THAN RING SIZE The extraordinary difficulty experienced in preparing 5-methoxy-8-phenyltetralone-1 (XXXVIII) from 7-(4-methoxy-3-biphenyl)-butyric acid (XXXVII) possibly may be explained by the hindering effect of the phenyl substituent ortho to the point of ring closure. The necessity of the acylation occurring meta to the methoxyl group does not seem to account fully for the behavior because 7-0-methoxyphenylbutyric/acid has been cyclized to 5-methoxytetralone-l in fair yield 24 and other ring closures meta to the methoxyl group are known. 15-26 Although XXXVII has been cyclized by means of hydrogen fluoride, the yield was very low. 16 24 Lockett and Short, J. Chem. Soc., 1939, 787. 86 R. T>. Haworth and Sheldrick, J. Chem. Soc., 1934, 1950....
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