0-Phenylpropionic acid, cyclization

The cyclizations of y-phenylbutyric acid (I) to tetralone-1 (II) and of /3-phenylpropionic acid (III) to hydrindone-1 (IV) exemplify a type of intramolecular acylation which has served as an important tool in the synthesis of polycyclic hydroaromatic and aromatic compounds.1-2 8... 

The Benzene Nucleus. The main problem in direction of cyclization is presented when both positions ortho to the acid side chain are available and ring closure into both would result in the formation of two isomeric ketones. In the benzene series the only acids having these structural properties are the meta substituted phenylbutyric and phenylpropionic acids, with which cyclization usually takes place at the position para to the substituent. Thus 6-methoxytetralone-l (LIV) was obtained14... 

Intramolecular Buchner reaction. Rh(OAc), is more efficient than CuCl as the catalyst for cyclization of the a-diazo ketone 1, derived from 3-phenylpropionic acid, to bicyclo 5.3.0]decatrienone (2). This product isomerizes in the presence of triethylamine to the more stable trienone 4. A useful isomerization to 3-tetralone (3) occurs in the presence of trifluoroacetic acid. 

Thomson and co-workers effected cyclizations such as /3-phenylpropionic acid 1-indanone (85%). -phenylbutyric acid - a-telralone (73%) by stirring a mixture of 2 g. of NiiCI and 10 g. of AICI, over a free flume until molten, stirring in 2 g. of acid with u thermometer at 140°, raising the temperature rapidly and keeping it at 180-200 for 2 minutes. The same procedure served fur Fries renrrangements, for condensation of hydruquinone with diacids, and fur cyclization of aryl vinyl... 

The Reformatsky reaction between 2-allylcycZohexanone and ethyl a-bromo-/3-phenylpropionate yielded the acid [l], which on cyclization gave two acids, one of which was the expected 13-allyl-derivative [li]. The other acid did not react with bromine and was allotted the structure [l 11 ] on Curtius degradation it afforded the amine [liii]. The acid [in] was recovered mainly unchanged after heating with spongy palladium at 310° C. for one hour [21]. 

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