DECEMBEE 1957
NOTES
1737
moles oi alkali are required by formula I for opening the rings and one for decarboxylation of the resultant isodehydroacetic acid analog. Phorone has been isolated as the product of this alkaline hydrolysis. Formation of phorone requires opening of both rings, decarboxylation a t both carboxyl groups, and isomerization of the double bond. The carbon chain in the dimer is established by the isolation of this degradation product. The spectral data for the dimer also confirm the structure I. Spectral analogies would be expected with the related open chain isopropyl isodehydroacetate (11).There is a remarkable parallel in the CHEMICAL LABORATORY data for these two materials. The dimer absorbs in OF TORONTO UNIVERSITY the ultraviolet a t 254 mp, log e 3.984; 294 mp, log e TORONTO 5, CANADA 3.698. Isopropyl isodehydroacetate absorbs a t 248 mp, log E 3.80; 295 mp, log E 3.78. The principal and characteristic infrared absorption bands occur 2-Pyrones. XXVIII. 4,7,7-Trimethyla t 1745 and 1718 cm.-l (2-pyrone and unsaturated delta lactone carbonyl stretching vibrations respec7,8-dihydro-(2H,SH)-pyrano-[4,3-b]tively); 1071 cm.-l (C=O stretching); and a t 850 pyran-2,5-dione crn.-I (ethylenic C-H rocking vibration band characteristic of 2-pyrones). The related absorption RICHARDH. WILEY,J. G. ESTERLE,K. F. HUSSUNG, bands for ethyl isodehydroacetate occur at 1754, C. L. DE SILVA,AND S. C. SLAYMAHER 1727, 1080, and 850 cm.-l The dimer differs from the ethyl ester in having a relatively strong absorpReceived May 20, 1957 tion band a t 1406 crn.-I, assignable to the C-H On numerous occasions over the past several bending vibration of the conjugated methylene years we have observed the formation of a solid by- group. In both structures the 2-pyrone carbonyl abproduct during the preparation of p-methylgluta- sorption is shifted to higher frequencies, a phenomconic anhydride. This solid, m.p. 154-155", is best enon previously noticed with 2-pyrones having prepared by distillation of P-methylglutaconic acid carbonyl substituents in the 5-positi0n.~ a t atmospheric pressure-a process that sometimes The pyrolysis of the dimer is a most interesting gives the anhydride and sometimes gives the by- reaction. The pyrolysis product, formed by heating product. Its empirical composition, ClIH1204, and the dimer to 350" in the presence of copper, is 4molecular weight of 204 correspond to the combina- me thyl-6- (2'-me thylpropenyl)-2-pyrone (111) obtion of two molecules of P-methylglutaconic acid tained by decarboxylative rearrangement of the with the loss of one molecule of carbon dioxide. At acyl glutaconic anhydride obtained in turn from various times we have considered several different senecioyl chloride and R-methylglutaconic anhystructural possibilities for this material based on dride. The infrared absorption characteristics of various types of condensations of two molecules of the products obtained by the two processes are the anhydride. Of these only that of 4,7,7-tri identical. The great diminution of the very strong methyl - 7,8 - dihydro - (2H15H)-pyran0 [4,3-b]pyran- band a t 1080 cm.-l, characteristic of the C-0 2,5-dione1 (I) is in accord with all of the physical stretching vibration in the unsaturated delta lacand chemical data now available to characterize tone structure of the dimer and one of the most this product. We now have confirmatory evidence prominent in its spectra, can be used to assess the for this structure which establishes it with reason- purity of the 2-pyrone in which this band is very able assurance. weak. It has been noted previously4 that 3,6-diMost structural possibilities, such as those based methyl-3-valerolactone is converted to isoheptanoic on Diels-Alder condensations, can be eliminated a t acid a t 216" in a similar reaction. once as the dimer shows no acidic, enolic, or ketonic This conversion of @-methylglutaconic anhyproperties and does not react readily with bromine. dride in two pyrolytic steps to 4-methyl-6-(2'Although the dimer does not dissolve in cold alkali methylpropenyl)-2-pyrone has suggested the comand cannot be saponified with aqueous or alcoholic bination of these two steps into one as a more dialkali, it does react quantitatively with three moles of potassium hydroxide on refluxing in ethylene gly(2) Richard H. Wiley, and S. C. Slaymaker, J . A m . Chem. col to give a saponification equivalent of 69. Two Soc., 78,2393 (1956). (3) Richard H. Wiley, and J. G. Esterle, J. Org. Chem., activated a t 200" for one day. Elution with hexane yielded successively the meso diastereomer and then the dd,11, isomer. Finally the column was eluted with methanol t o remove stilbene. The yields for diadduct-dioxahexane, 1:2 were 0.33 g. (35%) meso, 0.13 g. (14%) dd, 11, characterized by the absorption peak a t 280 mp and 0.39 g. (41%) of stilbene characterized by mixture melting point. The yields from diadducMioxahexane 2:l were 0.37 g. (39%) meeo, 0.18 g. (19%) dd, 11, and 0.31 g. (33%) of stilbene. The meso3,4-diphenylhexane was characterized by mixture melting point.' A comparable experiment with diethyl sulfate and the red residue from the monoadduct after hexane extraction to remove stilbene yielded meso and dd, 11-3,4-diphenylhexane in aratioof2.1:l.
(1) The product, ultimately identified as (I) will be referred to as the dimer in this discussion in the interests of brevity.
21,1335 (1956). (4) R. P. Linstead and H. N. Rydon, J. Chem. SOC.,580 (1933).
1738
VOL.
NOTES
rect route to this pyrone which is of interest as a possible intermediate or inhibitor in the biosynthesis of cholesterol. This direct synthesis has been achieved to give 35% yield of the pyrone from the acid. The acid is first heated to 250" a t atmospheric pressure for one hour and then, after addition of copper, to 300" for an additional hour during which time the pyrone distills from the reaction mixture. The formation of the dimer can be accounted for assuming a condensation in the linear anhydride (IV) between a methylene group and anhydride carbonyl followed by lactonization and decarboxylation or by a self-acylation of the anhydride and its decarboxylated product followed by a rearrangement in which the intermediate is lactonized rather than decarboxylated as in previously observed6 reactions of this type. There may be no fundamental difference in these two possibilities. In each the anhydride, or acid, carbonyl condenses a t the methylene carbon as a means of providing the carbon--carbon bond required to form the 2pyrone ring. Both have, however, been previously observed only as base-catalyzed reactions. The dimer has been obtained from the senecioyl chloride acylation of t,he anhydride which indicated the feasibility of the later reaction sequence. 0
" I/
CH3
22
min. Ten ml. of water was added to the cooled solution. The acidified solution was extracted with ether. The ether extracts were washed with aqueous sodium carbonate, dried, and evaporated to give a residue. Distillation of this residue gave 0.2 g. of material which gave a positive ketone test. The infrared spectra of this product was identical with that of an authentic sample of phorone. The dinitrophenylhydrazone, m.p. log", was prepared and gave no depression in melting point when a mixed melting point was run with an authentic sample. $-Methyl-6-(2'-methylpropenyl)-2-pyroneby pyrolysis of the dimer. A mixture of 5.0 g. (0.024 mole) of the high boiling fraction and 1.0 g. of copper powder was heated on a Wood's metal bath a t 270-290" for 1.5 hr. After the initial heating period the temperature of the bath was gradually raised to 350'. There was collected as distillate 1.7 g. (43%) of 4methyl-6-( 2 '-methylpropenyl)-2-pyrone. Refractionation gave a fraction b.p. 109'/1 mm., which was recrystallized from ether to give the pyrone, m.p. 45-46'. The infrared spectrum of the product was identical with that of an authentic sample of the pyrone prepared as previously described. .&Methyl-6-(%"-methylpropenyl )-B-pyrone by pyrolysis of ~"methylglutaconicacid. I n a 25-ml. distilling flask was placed 15.0 g. (0.104 mole) of crude 8-methylglutaconic acid. The flask was immersed in a Wood's metal bath previously heated t o 250". The crude acid melted and evolved carbon dioxide vigorously. A small amount of low boiling material was collected as distillate. After this initial reaction had subsided, the flask was heated for 1 hr. at 250" and then, after adding 1.0 g. of copper powder, at 300" for 1 hr. The temperature of the bath was then gradually raised to 360' during which time 3.1 g. (38%) of 4methyl-6-(2'-methylpropenyl)-2-pyrone was collected. The infrared spectrum of the product was identical with that of an authentic sample of the pyrone prepared as previously described.
Acknowledgment. The authors wish to acknowledge partial support of this research through grants from the Damon Runyon Memorial Fund, National Science Foundation, Eastman Kodak Company, and United States Public Health Service. DEPARTMENT OF CHEMISTXY UNIVERSITYOF LOUISVILLE LOUISVILLE 8, KY.
EXPERIMENTAL^ Preparation of the dimer (I). Fifty grams (0.35 mole) of P-methylglutaconic acid was placed in a 125-ml. Claisen flask with a receiver, an ebulator, and a thermometer. The pressure was reduced to 3 mm. The flask was heated t o 185' over a 0.5-hr. period. The temperature was held constant until the pressure which srtddenly rises t u 60 mm. dropped to 10 mm. The temperature was then again raised slowly and the ~iiatwiddistilling between 180 and 210' was collected. Upon recrystallizatikm from methanol 15 g. of niittwial, m.p. 154-155": w2:s obtained. Anal. Calcd. for C,lII,d14:C, 65.45; H, 5.81; sapon. equiv. 69.4; mol. wt. 208.4. Found: C, 63.36; H, 6.09; sapon. equiv., 69 (in ethylene glycol); mol. wt. 204 (Rast). Conversion of dimer Eo phorone. One gram (0.0048 mole) of the dimer wa.s Jlssolvec! in 20 mi. of I N potassium hydroxide iri ethyiene glyco!. The solution was heated siowly to 130' ovor a period of 30 mio. and held a t this temperature for 15
Some 1,s-Dinitrophenanthrene Derivatives CHARLESK. BRADSHER AND DOROTHY J . BEAVERS Received April 22, 1957
I n earlier experiments, directed toward the synthesis of dinitrophenanthrene derivatives, it w a found that 3,5-dinitro-2-chlorobiphcny~ (1) with NO2 ?yN02
},
TAC1 cooc2IIs
Y , ~NO1
~
$. .v
CH,COCH Na)
I (5) Richard ki. Riiej and X R. Smith, J . An?. C!Lem. Soc., 74,3893 (1952; ( 6 ; Analysee by X i c r o Tech I,aboratorirs, dkckie, 111.
U2K
-
--)-
\.C H - C O O C I F ~ ~
,:c' b-CH , 1
1:
t
(1) @. K. Bradsher and S T. izmore, J . Am. C b r n hoc., 66,1283 (1944).
