THIONAPHTHENEQUINONES
Sept., 1935
1611
(XIII). Almost colorless, yielding solutions with marked then from hot ethyl alcohol, or vice uetxa, seems to give a blue fluorescence, it melts on recrystallization from acetone solvent-free product. No fluorescence of the original carbinol (VII) in solution could be detected, but on addiand methyl alcohol at 160'. Anal. Calcd. for C Z ~ H ~ ZC,O86.52; ~: H, 5.52. Found: tion of acid and slightest warming, a marked blue fluorescence was noticeable. C, 86.57; H, 5.68. On bromination, oxidation, acetylation, and treatment Reaction with Hydrogen Halides.-Treatment of (VII) with dry hydrogen halides, this substance behaves exactly in ether solution with dry hydrogen chloride and hydrogen like the dihydroanthranol (VII) and yields identically the bromide yields the wchloro and bromo derivatives (XIII). Treatment with thionyl chloride in the cold yields the same same products as have already been described. Molecular Silver on Bromo Compound (XIII).-The brochloride, m . p. 189', as yellow needles, highly fluorescent. mide (XIII), warmed for a short time in benzene solution And. Calcd. for C27H19Cl: C, 85.55; H, 5.07. Found: with molecular silver, is converted into a yellow, highly C, 85.35: H, 5.06. fluorescent substance, m. p. 252-253', recrystallized from The bromide, m. p. 188", was obtained as described benzene-petroleum ether. above, and also by brominating 9-phenyl-10-benzylanthra- Anal. Calcd. for Cs4H38: C, 94.46; H, 5.54; mol. wt. cene in carbon disulfide solution. No bromine was ab- 686. Found: C, 94.06; H, 5.53; mol. wt. (Rast, camsorbed in the cold in the latter reaction and when reaction phor), 524. began on warming slightly, hydrogen bromide evolution summary immediately took place. It was recrystallized from car1. The Grignard reagent adds 1,6- t o methylbon disulfide and ether. Anal. Calcd. for Cg7HlgBr: C, 76.56; H, 4.54. Found: eneanthrone. C, 76.14; H, 4.81. 2. 10-Alkylanthranols readily yield crystalline 9-Phenyl-10-w-oxybenzylanthracene (VU).-A solu- peroxides with atmospheric oxygen and these tion of 7 g. of the dihydroanthranol (VII) in 40 cc. of ace- peroxides suffer smooth pyrolysis to anthraquitone and 5 cc. of 10% sulfuric acid was warmed on the none and alcohols formed by 1,4-elimination. water-bath until insoluble and high melting material began 3. lO-Alkyl-9,10-dihydroanthranols are readily to separate (one hour). The solution was then filtered, poured into water and extracted with ether. The residue converted into anthracene derivatives, either by from evaporation of the washed and dried ether solution 1,4-elimination of substituents or by migration was recrystallized, first from alcohol, then from acetone and of groups. petroleum ether, m. p. 187'; yield 6.2 g., highly fluorescent 4. A five-carbon atom isomerism in anthracene in solution. derivatives similar t o the threecarbon atom isoAnal. Calcd. for Cz,HmO: C, 89.96; H, 5.60. Found: merism in allyl compounds is conclusively demonC, 89.65; H, 5.68. strated in the case of 9-phenyl-10-benzylideneThis compound seems to crystallize both with alcohol and acetone of crystallization, the solvent being lost be- 9,lO-dihydroanthranol-9. INDIANA RECEIVED JUNE 17, 1935 tween 70 and 80". Recrystallization from acetone first, GREENCASTLE,
1 CONTRIBUTION FROM
THE
CHEMICAL LABORATORY O F HARVARD UNIVERSITY]
A Comparison of Heterocyclic Systems with Benzene.l nones
IV.
Thionaphthenequi-
B Y LOUISF. FIESERA N D R. GRICEKENNELLY
This series of investigations was undertaken with the idea that a comparison of the lowering in the reduction potential of a quinone resulting from the fusing of an unsaturated heterocyclic ring to the quinonoid ethylene linkage, with the lowering in potential produced by a benzene ring in the corresponding position, might afford a means of determining the degree of aromaticity of the heterocycle with respect to benzene. Fieser and Arneslt' studied two quinones containing the (11 previous papers: ( a ) Fieser. '~"lb: I[JIIKNAL. 48, 1097 (1926): ill) Ijiebcr atld .4mea, m i d , 49, 2804 (1Y27l; ( c ) Fiesrr and Peters,
ibrd , 69, 4080 I 1931 1
thiophene nucleus, but each of these was of a rather special structural type. The purpose of the present work was t o prepare and characterize simple ortho and para quinones derived from thionaphthene with the quinone grouping located in the carbocyclic ring. The problem was largely a preparative one, for few quinones of the desired type have been described previously, and hydroxythionaphthenes suitable for use as starting materials are either unknown or rather inaccessible. The only route to the hydroxy compounds is by synthesis, since
LOUISF. FIESER A N D R. GRICEKENNELLY
1612
substitutions attack thionaphthene a t the C3 position2 in the heterocyclic ring.3 A synthesis of 5-hydroxythionaphthene (VI) recently has been reported by Fries4and described in detail by Hemmecke,6 and we have found the method of great service in obtaining a typical ortho quinone of the series. The starting material, 2-chloro-5-nitrobenzaldehyde, I, is converted through the disulfide t o the sulfhydryl compound 11, and on reaction with chloroacetic acid and ring closure
I /I
tion of 5-hydroxpthionaphthene by the usual method proceeded poorly, but the zinc salt of the nitroso compound was obtained easily by the method of Henriques and llinski,' and it could be converted into the sodium salt with little loss. The sodium salt reacted easily with sodium bisulfite to give 4-amino-5-hydroxythionaphthene7-sulfonic acid, and this on oxidation yielded the o-quinone, which was isolated as the crystalline red potassium salt VII. The reaction of this
CHO
02N\//\/CHO
0
CHaO
I1
I
0
,!(, \ -
+
+
Vol. 57
i s
SOaK
0
V I II
VI1
TI1
+HO\[). IV
02N\Q
\/
\/\,
v
VI
S
quinone with methyl alcohol and sulfuric acid proceeded as in the naphthalene series,8giving the methoxy-p-thionaphthenequinone VIII. As the starting point for the preparation of the unsubstituted para quinone, either 4-hydroxythionaphthene or 7-hydroxythionaphthene was required. The former compound has been obtained previously in very poor yields by the condensation of a-thiophene aldehyde with sodium succinate, and the isomer is not known. We decided to attempt a new synthesis. The Friedel and Crafts reaction of thiophene with succinic anhydride in either nitrobenzene or carbon bisulfide gave in fair yield a keto acid which very probably has the structure of IX. That the substitution occurs a t the a-position is inferred from the course of the condensations with phthalic anhydride'* and with acyl All types of substitutions, in fact, yield chiefly the aderivatives. Reduction of the keto acid to ?-(athieny1)-butyric acid (X) by the Clemmensen
5-nitrothionaphthene-2-carboxylic acid, IV, is obtained. Hemmecke reduced the nitro compound and decarboxylated the resulting amine, but we found i t somewhat more convenient to decarboxylate IV with copper powder in quinoline solution6 and to reduce the 5-nitro compound, V. Our over-all yield of 5-hydroxythionaphthene in five steps from o-chlorobenzaldehyde was 5%. All attempts to prepare 4,5-thionaphthenequinone were unsuccessful. 4-Amino-5-hydroxythionaphthene hydrochloride was obtained in a highly pure condition (through the azo dye), but it yielded only a black, sparingly soluble substance on oxidation. We were able to characterize potentiometrically the oxidation step to the __ quinoneimine, but the quinone itself was not + obtained. A stable derivative suitable for po- \s \COCH~CH,COOH+ \CH~CH~CH~CO~H tentiometric study was found, however, in poIX X tassium 4,5-thionaphthenequinone-7-sulfonate, OH VII, which was prepared as follows. The nitrosaCO I
I/ )
u
-/\.
(2) Numbering system (German convention): 5
6us/2 7
1
(3) Fries and Hemmecke, Ann., 4 7 0 , l (1929); Komppa and Weckman, J . prokt. Chcm., 138.109 (1933). (4) Fries, Ann., 464, 126 (1927). (6) E.Hemmecke, Dissertation, Braunschweig, 1929. (6, Shepard, Winslow s i 1 1 I Johnson, THIS J O V K N , ~ I . , 12, '_'OX:{ (1930).
S
CH2
XI
(7) Henriques and Ilinski, Rer., 18, 704 (1885). (8) Fieser, THISJOURNAL. 48, 2922 (1026). (9) Biedermann, Ber., 19, 1617 (1886). (10) Steinkopf. .Inn., 407, 94 (1!115). h11) Scheibler and Reftig, BEr., 19, ll',I4 (1!l?tjI. [ 121 V b f w c r . 1,ir ' " ~ ~ ~ ~ i ~ ~ i M ~ W t ~ , 131) ~ i IT,: i
S XI1
~ Irt ' 8~t i ~ i ~ ~ ~ ~ , "
THIONAPHTHENEQTJINONES
Sept., 1935
1613
method was best accomplished by the low- which includes for comparison values for the temperature procedure, l 3 for the thiophene nu- normal potentials of the corresponding naphthocleus appears to be sensitive to the action of quinones. strong hydrochloric acid a t the boiling point. TABLE I For the same reason aluminum chloride proved NORMAL REDUCTION POTENTIALS (26") to be too active a reagent for the ring closure of X Solvents: A, aqueous buffer; B, 50% alcohol, 0.1 N through the acid chloride. Using anhydrous in HCI and 0.2 N in LiCl; C, 37% alcohol, 0.047 M in KHzPOl and 0.047 M in NazHP04. Titrating agents: stannic chloride, a milder reagent which has been TB tetrabromo-o-benzoquinone; KD = K2Cr207; KM used with success in the thiophene series14 and = &Mo(CN)s. Kormal with other particularly reactive aromatic sysTitrated potential, Eo (av.), v. System, named as oxidant Solvent with terns,I5 4-keto-4,5,6,7-tetrahydrothionaphthene, KD 0.540 4,7-Thionaphthene- A (HC1) XI, was obtained in 90% yield. DehydrogenaTB ,559 quinone (XIII) B tion of the ketone to the desired 4-hydroxy- a-Naphthoquinone A (HCl) ,47018 B ,48417 thionaphthene was accomplished in 46% yield with the use of sulfur. The hydroxy compound Pot. 4,5-Thionaphthenequinone-7A (PH4.9, always was accompanied by a neutral fraction sulfonate (VU) pH 6.2) KM ,705 probably containing thionaphthene formed by Pot. l,&Naphthothe elimination of the elements of water. The quinone-4-sulfonate A . 6301" yield was very poor when selenium was used, 4,5-Thionaphthenequinone-4-imine C KM .70018 probably because of the slower dehydrogenating action and because of the destruction of the 1,2-Naphthoquinone1-imine C KM .62218 phenolic substance a t the higher reaction temperature. The best over-all yield of 4-hydroxythioVarious comparisons between the heterocyclic naphthene from thiophene was 14.5%. and the carbocyclic systems can be made and the An amino grou!p was introduced by the reduc- results are all concordant. The para quinone tion of the p-sulfobenzeneazo compound, and on derived from thionaphthene has a potential in oxidation there was obtained 4,7-thionaphthene- aqueous solution 70 mv. higher than that of aquinone, XIII, 5% crystalline, yellow compound naphthoquinone, and in alcoholic solution the very similar in properties to a-naphthoquinone. difference is 75 mv. The heterocyclic ortho quinone sulfonate is 75 mv. higher in potential 0 OAc than the naphthalene derivative. The P-thioACZO naphthenequinone itself is not available, but a comparison is possible between the ortho quinoneHzSOP 0 imines of the thionaphthene and the naphthalene series, even though these substances are extremely XIII: unstable, and the difference in this case amounts Since the conjugated system of the quinone is to 78 mv. Clearly the EO value for substances unsymmetrical, there are two paths open for 1,4- of quite different structural types is an essentially addition reactions. In the one example studied, constant quantity. namely, the Thiele reaction, the only product As judged by the criterion of these oxidoisolated (33% yield) was that formed by addition reduction potentials, the thiophene ring is disto the system terminating in the C7-carbonyl tinctly less aromatic than benzene. The effect of group, giving the triacetate XIV. The structure fusing a benzene ring to ortho or para benzowas established by converting the substance into quinone is to lower the potential by 231 rnv.I9 a methoxythionaphthenequinone which proved The average effect of the thiophene ring is 156 to be identical with the compound VI11 obtained (16) La Mer and Baker, THIS JOURNAL, 44, 1960 (1922). (17) Fieser and Fieser, ibid., 66, 1565 (1934). in the other series of experiments. (16) Determined by the method of discontinuous titration ( i b i d . , A summary of the results of the potentiometric 52, 4915 (1930)). The figure reported is in each case the average of determinations agreeing within 1 mv. The values for the study of the nen quinones is given in Table I, seven constant C were 0.97 and 1.23, respectively; the initial rates of =i
'
