J . Org. Chem. Vol. 37, No 11, 1972 1807
5- AND 6-FLUOROBENZO[CIPHENANTHRENE pounds X and 20 were better resolved on column I11 at loo”, giving retention times of 38.9 and 39.3 min, respectively. Kinetic Measurements. A. Anhydrous Acetic Acid.4oAnhydrous acetic acid was prepared by refluxing reagent grade glacial acetic acid with 10% acetic anhydride and a catalytic amount of concentrated sulfuric acid. After having been refluxed for 12 hr, the acetic acid was distilled through a 30-plate perforated-glass column and collected over the range 117-117.5’. The acetic acid was stored in a flask equipped with a siphon-type arrangement so that it could be removed using a positive pressure of dry nitrogen without exposing i t to air. B. Titrations:-Titrations of acetic acid solutions of p-toluenesulfonic acid with sodium acetate in acetic acid were accomplished potentiometrically on a Potentiograph E 336 (Metrohm Ltd., Herisau, Switzerland). The sodium acetate solution, approximately 0.05 M , was obtained by dissolving anhydrous, reagent grade sodium acetate in anhydrous glacial acetic acid and making the solution up to volume. The sodium acetate solution was standardized against 0.0527 M perchloric acid in acetic acid C. Rate Measurements.-Solutions 0.05 M in the compounds to be solvolyzed were made up at room temperature in a volumetric flask from a weighed portion of the tosylate and anhydrous acetic acid. About 3-ml portions of the solutions were sealed in 10 ml color-break ampoules (Kimble Neutraglas) under nitrogen and immersed in a 100” oil thermostat. The exact temperature of the bath was obtained from a Beckman thermometer which had been previously calibrated with a quartz thermometer (Hewlett-Packard, Inc., Quartz Thermometer No. 2801A). At suitable times an ampoule was removed and placed in a dewar of Dry Ice-isopropyl alcohol until all samples could be titrated together. Approximately 12 samples were taken during each run, spaced evenly over the first two to four half-lives. An additional one to three samples were taken for infinity points. The samples were brought to room temperature and opened. (40) The procedure was adapted from the Ph.D. thesis of H . A. Hammond, “Studies of Acetolysis Rates of Arylmethyl p-Toluenesulfonates,” University of California, Berkeley, Calif., 1966.
A 2-ml aliquot was removed with a Chaney syringe adjusted to deliver a constant volume. The 2-ml volume was standardized by weighing the volume of distilled water delivered by the syringe. Each aliquot was diluted to approximately 15 ml with glacial acetic acid and titrated potentiometrically. Rate constants were obtained using a nonlinear least-squares computer program LSKIN 141 which calculates the best value of the first-order rate constant. The infinity titer was treated as a fixed parameter. The standard deviations of the rate constants, as calculated by the computer, showed the precision of the measurements to be good, the error limits obtained generally being less than *3% of the observed rate constants. Results are presented in Table 111.
Registry No.-1, 22489-58-3; 2, 34217-23-7; 3-d, 34217-24-8; 4, 34217-25-9; 6 , 34217-26-0; 8 , 3421727-1; 9, 34217-28-2; 10 ketal alcohol, 34217-29-3; 12, 34217-30-6; 14, 34217-31-7; 18, 21789-58-2; 19, 22489-59-4; 19 DNP, 34217-34-0; 19 semicarbazone, 34217-35-1 ; 20, 22489-60-7; 22, 34217-37-3; 23,34217-38-4; 24, 34217-39-5; 25 (trans), 21370-71-8; 26, 34217-41-9; 27, 34217-42-0; 30, 13031-01-1; 31 (trans), 5365-38-8; 32, 34217-44-2; 33, 22460-14-6; 37,15674-93-8; 54 DKP, 22460-13-5. Acknowledgments.-We gratefully acknowledge financial assistance by the National Science Foundation and the Committee on Research, Berkeley Division, University of California. We also thank hlr. Clayton Quinn for technical assistance and Professor Donald Noyce for several stimulating discussions on the subject. (41) D. F. DeTar and C. E. DeTar, “Computer Programs for Chemistry,” Vol. I, W. A. Benjamin, New York, N. Y., 1969.
Synthesis of 5- and 6-Fluorobenzo[c]phenanthreneby Photocyclization GERARD S . MARXAND E. D . BERGMANN * Department of Chemistry, Hebrew University, Jerusalem, Israel Received September 8, 1971 5- and 6-fluorobenzo[clphenanthrene (1, 2 ) were synthesized by photocyclization of the appropriately substituted 1-naphthyl-2-phenylethylenes. Various synthetic schemes for obtaining 1,3-disubstituted naphthalenes have been studied. The uv spectra of key compounds are tabulated.
Interest in fluoro analogs of polycyclic aromatic compounds stems from the hope that they may help evolve a model of chemically induced carcinogenicity.’ We have synthesized the title compounds by photocyclieation of the appropriately fluorinated diarylethylene~.~-~ An intrinsic expectation of the synthetic approach to 1 and 2 was that the photodehydrogenation or photocyclization step would occur on the 4 carbon of the naphthalene i o i e t y . This expectation was bolstered by the statement6 that the formation of phenanthrene moieties from stilbenelike compounds is possible if the sum of the free valence numbers in the first excited state (Z Fr”) of the appropriate carbon is greater than 1.0. (1) E. D . Bergmann and J. Blum, J . Org. Chem., 27, 527 (1962). (2) J. Blum, F. Grauer, and E. D . Bergmann, Tetrahedron, 2S, 3501 (1969). (3) S. .M. Kupchan and H. C. Warmser, Tetrahedron Lett., 3792 (1965); J . O w . Chem., 80, 3792 (1965). (4) T . Sata, S. Shimada, and K. Hata, BuLl. Chem. S o c . Jap., 42, 766 (1969). ( 5 ) W.H. Laarhoven, T . J. Cuppen, and R. J. Nivard, Reel. Trau. Chim.. Pays-Bas, 87, 687 (1968).
q$WFT F 1
2
3a,R=H b,R=I
I .
4a,R=H b,R=I
sa, X = NH,; Y CO,H b, X = NH,; Y = C02Me c,X = F; Y = CO.,Me d,X= F; Y = CH,OH e,X = F; Y = CHIBr 5
1808 J. Org. Chem. Vol. 37, No. 11, 1972
MARXAND BERGMANN
Such calculations were carried out and gave values of 2 Fr* = 1.169 (3a) and 1.173 (4a). 6-Fluorobenxo [clphenanthrene (1) indeed was formed by the photolysis of either the ethylene 3a or 3b. Precursor 3a gave yields ranging from 52% (without addition of 1 2 ) to 82% (in the presence of the halogen), while 3b gave >91%. Compounds 3a and 3b were obtained from 2-aminonaphthalene-3-carboxylicacid (Sa), which was sequentially converted t o 5e by straightforward reactions. Homer-Wittig reaction of 5e with either benzaldehyde or o-iodobenzaldehyde gave 3a or 3b. Compound 2 proved to be much more difficult t o obtain, since the overall yield in the multistep synthesis of the key compound 1-fluoro-3-bromonaphthalene (9) is very low. A number of pathways were explored. Scheme I involved the reduction of 1-fluoro-4-nitro-
F I
SCHEME I F I
NO?
6
NH2
SCHEME I1
rl.0, 10
11
@qBr - @yBr -
carboxylic acid (22). The inability of fluoronitrobenzenes to undergo the von Richter reaction has been remarked on.'O Our attempts to duplicate the reported procedure for the synthesis of 1-amino-3-cyanonaphthaleneby fusion of sodium l-aminonaphthalene-3-s~lfonate~~ with potassium cyanide gave only traces of 15. A further synthesis of 9 was effected by a route starting from tetralin (Scheme 111).16-18 This procedure, too, gave only low yields (overall
