Phenanthrene synthesis

The acid 19 has been dimerized, although in low yield, in the course of a perhydro-phenanthrene synthesis [141]. When the oxidation potential of the double bond is sufficiently lowered by alkyl substituents, lactone formation by oxidation of the couble bond rather than of the carboxyl group occurs (Eq. 7) [142] (see also chap. 15). 

Pschorr, R. Ber. Dtsch. Chem. Ges. 1896, 29, 496. Robert Pschorr (1868—1930), born in Munich, Germany, studied under von Baeyer, Bamberger, Knorr, and Fischer. He became an assistant professor in 1899 at Berlin where he discovered the phenanthrene synthesis. During WWl, Pschorr served as a major in the German Army. 

Cohare and co-workers reported that aristolactam BU (22) was prepared, following Kupchen s method, by Perkin condensation of 6-bromo-3,4-di-methoxy phenyl acetic acid (119) and o-nitrobenzaldehyde (120) (Scheme 14). The 2-bromo-4,5-dimethoxy-2 -nitro-ds-stilbene-a-carboxylic acid (121) was obtained. The nitro group of 121 was reduced with ferrous sulfate and ammonium hydroxide, and the resulting 2-bromo-4,5-dimethoxy-2 -amino-cw-stilbene-a-carboxylic acid (122) without purification was submitted to the Pschorr phenanthrene synthesis to yield l-bromo-3,4-dimethoxyphen-anthrene-lO-carboxylic acid (123). The phenanthrylamine 124 was prepared from 123 via a Schmidt reaction, and, by treatment with n-butyllithium and CO2, 124, afforded 22 (42). 

The Bardhan-Sengupta Phenanthrene Synthesis uses P2Os in place of H2SO . 

On naphthalene based starting materials, a phenanthrene is produced and the reaction is called the Hayworth Phenanthrene Synthesis ... 

Phenanthrene synthesis. Treatment of (Z)-2-chlorostilbenes, available by Wittig reactions with 2-chlorobenzaldehydes, with Riecke activated magnesium in refluxing THF (12 hours) produces phenanthrenes (64-83% yield). (Z)-2-Bromostilbenes are reduced and isomerized to (E)-stilbenes by activated magnesium. The phenanthrene synthesis involves radical intermediates.2... 

Scheme 15. Isoxazole-appended phenanthrene synthesis by PIFA-mediated oxidative cyclization.

Phenanthrene synthesis. A new phenanthrene synthesis employs the nickel(O)-catalyzed condensation of the imine 1 with 2 to give, after hydrolysis, the aldehyde 3. This product was converted in several steps to the phenanthrene 4, which is a key... 

Haworth phenanthrene synthesis. Acylation of aromatic compounds with aliphatic dibasic acid anhydrides to (i-aroylpropionic acids, reduction of the carbonyl group according to Clemmensen or Wolff-Kishner procedures, cyclization of the y-arylbutyric acid with 85% sulfuric acid, and conversion of the cyclic ketone to polycyclic hydroaromatic and subsequently to aromatic compounds. 

Hofmann degradation of N-methylthebenine dimethyl ether methiodide or methomethylsulphate, which result from the complete methylation of thebenine, affords 3 4 8-trimethoxy-5-vinylphenan-threne [vn], the 4-methoxyl group of which is so readily hydrolysed that boiling with acetic acid or alcoholic hydrogen chloride results in formation of methebenol and bromination in formation of bromo-methebenol [8], 3 4 8-Trimethoxy-5-vinylphenanthrene can be reduced to 3 4 8-trimethoxy-5-ethylphenanthrene, identical with a specimen prepared from 2-nitroveratric aldehyde and 2-methoxy-5-ethylphenyl-acetic acid by the Pschorr phenanthrene synthesis [11]. 

Ramana, M. N. V. and Potnis, R V. 1996. Tandem acylation-cycloalkylation a novel synthesis of phenanthrenes. Synthesis 1090-1092. 

For an excellent overview of Pschorr phenanthrene synthesis see D.F. DeTar, Organic Reactions, 9, (1957), 409. 

Another Friedel-Crafts route to phenanthrenes is the Bardhan-Sengupta phenanthrene synthesis. When phenethylcyclohexanol 222 was cyclized with phosphorus pentoxide at 140°C, the product was 223. Aromatization was accomplished by heating with selenium to give the phenanthrene derivative 224 (1-methyl-7-isopropylphenanthrene, otherwise known as retene). An improvement in the reaction used hydrogen fluoride (HF) to induce cyclization.l ... 

Structure. The structure of glaucine was arrived at by Gadamer (12) by a process of intuitive reasoning supplemented by a synthesis. Co-rytuberine dimethyl ether and glaucine were known to be isomeric, and if a relation to papaverine were admitted only two structures were available for the two alkaloids. Pschorr (13), utilizing his well-known phenanthrene synthesis, had attempted to convert papaverine into an aporphine (IV) via the nitro (II) and the amino (III) derivatives. When papaverine is nitrated it yields 6 -nitropapaverine (II), from which the methochloride... 

We have observed that by simply changing the base from K2CO3 to NaOAc in the phenanthrene synthesis shown in Eq. 83, we can obtain good yields of 9-alkylidene-9ff-fluorenes instead (Eq. 86) [154,155]. 

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