STUDIES RELATED TO THE SYNTHESIS OF MOLECULES OF CARBON(,3) SYMMETRY (ACYLATION, ETHERIFICATION, PHENALENES)

GEORGE KVAKOVSZKY, Purdue University

Abstract

The work reported detailed synthetic approaches to precursors for 2,4,5,7,8,9b(alpha)-hexahydro-1H-phenalene (I). The unique structure, possessing only a C(,3) symmetry element, makes (I) inherently chiral and an interesting test case of theories of optical rotatory power. One unsuccessful synthetic approach was based on 1,5,9-cyclodecatriene (II). Another approach involved several parallel synthetic schemes based on 1,6-naphthalenediol (III). Conversion of (II) to c,c,t-perhydro-9b-boraphenalene was followed by ruthenium tetroxide oxidation to 1,5,9-cyclododecatrione (IV). Due to the tendency of (IV) to undergo intramolecular aldol condensation this route to hexahydrophenalene was abandoned. Rate data from the acid catalyzed etherification of 1- and 2- naphthols with methanol was used to predict the composition of etherification mixtures derived from 1,6-naphthalenediol. The experimental data was fitted with reversible, second order rate equations. In addition to 1,6-dimethoxynaphthalene (V) a mixture isomeric monoethers was obtained. Reduction of 2-methoxynaphthalene with sodium in refluxing ethanol gave 2-tetralone (VI). The analogous reaction of (V) yielded 5- methoxy-2-tetralone (VII). The reaction of pyrrolidine and morpholine with (VI) and (VII) gave, after azeotropic distillation of water, the corresponding enamines. Alkylation with acrylonitrile in methanol of the morpholine enamine derived from (VI) and (VII) gave, after acidic hydrolysis, the monosubstituted products 1-(2-carboxyethyl)-2-tetralone (VIII) and 1-(2-carboxyethyl)-5-methoxy-2-tetralone (IX), respectively. An alternative route to (VIII) involved alkylation of 1-carbethoxy-2-tetralone (X) and subsequent hydrolysis. Mechanisms for the formation of (VI) and 3,4-benzaheptane-1,7-dicarboxylic acid (XI) via base hydrolysis of (X) was described. Attempts to cyclize (IX) to a precursor of (I) were carried out in polyphosphoric acid, PPA. Related PPA reactions of acrylic acid with aryl ethers, including anisole and (V), were also investigated. The reaction with anisole gave 4,4'-dimethoxydihydrochalkone (XXII), together with a trace of the expected vinyl ketone. The reaction with (V) yielded 2,3-dihydro-4,7-dimethoxy-1H-phenalen-1-one (XII), a precursor for (I).

Degree

Ph.D.

Subject Area

Organic chemistry

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