C . G. OVERBERGER AND JEAN-PIERRE ANSELME
658
Vol. 86
examples, cis-2-butene-l,4-diol itself (21) and its 2.3each, but both peak areas should be added together t o dimethyl derivative (23) both have low Av's (130, and 90 make a more valid comparison. .llkyl groups aiso cm.-l, respectively) and very weak bonded peaks generally reduce the ireelbonded intensity ratios. A (free bonded intensity ratios 5.5 and 4.1). The unsingle substituent, such as methyl (a), permits the symmetrical character of 2-methyl-cis-2-butene-l,4- butane chain to adopt an orientation favoring hydrogen diol (22) evidently is propitious for hydrogen bondbonding without increase in nonbonded repulsions ; ing, since both Au (14s cm.-l) and the free 'bonded inthe C4-carboncan as easily be trans to the methyl group tensity ratio (2.1) are improved. a t C p as trans to the C1 carbon. The "gem-dialkyl Free 'Bonded Intensity Ratios-n;hen a proton effect''-the heightened tendency toward ring formadonor and a proton acceptor group are placed a t diftion of alkyl chains bearing alkyl substituents, especiferent ends of a hydrocarbon chain, ring formation ally when geminal-has its chief origin in such steric through intramolecular association is opposed by the influences.' The trend is best illustrated here by comnatural tendency of the chain to adopt a linear, zig-zag paring planimeter peak area ratios, .-If '.Ab, for the series: conformation. With a,w-diols proton donor and acbutane-l,4-diol (l), 1.0; 2-methylbutane-1,l-diol ( 2 ) , ceptor groups are both moderately strong ; the hydro0 . 6 ; and 2,2-dimethylbutane-l,4-diol ( 3 ) , 0.33. In gen bond between them is suficiently energetic to most of the other more complicated molecules, subensure that association persists to a large measure even stituents also favor intramolecular hydrogen bonding. in 1,&-diols,but intramolecular hydrogen bonding falls Compound 4 appears to be anomalous in this respect. off drastically in 1,s-diols. Although strictly not din-e make no claim to understanding the fine details of rectly comparable, the free bonded intensity ratios of substituent effects. Perhaps the pronounced nonterminal diols give a convincing indication of this: bonded interactions in these molecules, many of them Ethylene glycol = 1.3, propane-l,3-diol = 2,0,7 buquite crowded, vitiate simple analysis. tane-l,A-diol (1) = 2.6, and pentane-1,j-diol = ca. One further influence of substituents is noteworthy ; 4.0.' they seem to favor the adoption of more than one conformation and two peaks often appear in the spectra. Any conformational effect which would facilitate This influence is seen most clearly in the series 1, 2 , 8, ring formation should increase the percentage of molebut we do not have an entirely satisfying explanation. cules engaged in intramolecular hydrogen bonding and Extensions of this work to 1,5- and 1,B-diols have decrease the free 'bonded intensity ratio. Ordinarily been completed, and the results will appear shortly.' nonbonded skew butane type repulsions would tend to Further illustrations of the effects described above are favor the adoption of a trans conformation for the even more dramatically exemplified in longer chain butane-l,d-diol chain ; this nonbonding conformation molecules. competes with hydrogen bond ring formation. If the hydroxymethylene groups of a 1,4-diol are attached to a Acknowledgments.-We wish to thank Dr. J. ring, the nonbonding conformation is not possible ; Meinwald, Dr. A. G. Cook, Dr. A. T. Blornquist, Dr. considerably reduced free "bonded intensity ratios are J . Sicher, and Dr. N. L. Allinger for supplying comobserved for almost all monocyclic and bicyclic diols pounds used in this research. Partial support of this (Table I ) . Molecules with more than one bonded peak project by a grant from the National Science Foundation to P. R. S. is acknowledged with appreciation. (such as 33-36, 39, 40, and 41) display higher ratios for
[CONTRIBUTION FROM
THE
DEPARTMENT OF CHEMISTRY, POLYTECHNIC INSTITUTE OF BROOKLYN, BROOKLYN 1, N Y ]
Azo Compounds. Five-Membered Cyclic Azo Compounds. Their Stereospecific Decomposition BY C. G. OYERBERGER AND JEAN-PIERRE XNSELME~ RECEIVED AUGUST20, 1963
Two cyclic five-membered azo compounds, 3,j-diphen?-l-l-pyrazoline and 3,5bis-(p-chlorophenyl)-1-pyrazoline, have been prepared. Their stereospecific decomposition to the corresponding trans-1,2-diarylcyclopropanes is reported and t h e mechanism of the decomposition is discussed.
Introduction Five-membered ring azo compounds (1-pyrazolines) having an a-hydrogen and capable of rearranging to a conjugated system, usually isomerize to the more stable 2 - p y r a ~ o l i n e s . ~However, as a part of our general studies of cyclic azo compounds, we decided to synthe(IjAr = C6H5) and study size 3,j-diphenyl-1-pyrazoline its chemistry. There were no previous authenticated reports of stable 1-pyrazolines of this type. The mechanism of the decomposition of both 1- and 2-py\ 1) ia'1 This is t h e 43rd in a series of papers concerned with t h e preparation and t h e decomposition of azo compounds For t h e previous paper in this series, see C G Overberger. J - P Anselme. a n d J R Hall, J A m Chem. Soc , 85, 2752 11963). ( b ) For a preliminary report of this work. see C. G Overberger and J-P. Anselme, i b i d , 8 4 , 869 (1962) ( 2 ) This paper comprises a portion of a dissertation submitted by JeanPierre Anselme in partial fulfillment of t h e requirements for t h e degree of Doctor of Philosophy in t h e G r a d u a t e School of t h e Polytechnic I n s t i t u t e of Brooklyn (3) T I.. Jacobs in R. Elderfield, "Heterocyclic Compounds," Vol. 5 , John Wiley and Sons, Inc., New York, S . Y . , 1957, p . 7 2 .
razolines has been the subject of a controversy which is still not settled a t present. It was hoped t h a t the decomposition of 3,5-diphenyl-l-pyrazolinewould shed some light on the problem. Results and Discussion One of the most general methods for the synthesis of 1-pyrazolines consists in the addition of an olefin to a diazoalkane. The reaction of styrene with phenyldiazomethane resulted in the formation of a white crystalline solid which melted with decomposition. The infrared spectrum had no absorption indicating the presence of -N-H and had a sharp peak of moderate intensity a t 1548 cm.-l, assigned t o the azo linkage. The product from the thermal decomposition was pure trans-1,2-diphenylcyclopropane. The structure of the pyrazoline was confirmed by its isomerization to 8,5diphenyl-2-pyrazoline (111, Xr = C6H5)isolated as its N-acetyl derivative ( I V , Xr = CeH5). It was identical
Feb. 20, 1964
FIVE-MEMBERED CYCLICAzo COMPOUNDS
with the N-acetyl derivative prepared from 3,5-diphenyl-2-pyrazoline. Ar
+
\
-
N=N
K=NCHAr
/
I1
iH+ 0
I1
ArCH=CHCAr
+ XHzNHz
+
/ ArHC \
CH,
N-N
I
H
CHz
\ CAr // I11
/
ArHC
\
AczO
+
N-N
\ CAr //
659
clusive formation of the tra,ns-l,2-diarylcyclopropanes, since if a triplet state were formed, the coupling should not be stereospecific.4 The photolytic decomposition of 3,5-diphenyl-l-pyrazoline a t 15' gave trans-l,2-diphenylcyclopropane as the $ole product, a result identical with that of the thermal decomposition. Coupled with the e.s.r. studies, this would suggest a free radical mechanism for the thermal decomposition of 3,5-diaryl1-pyrazolines. Thus, using the free radical mechanism as a working hypothesis, the various steps in the decomposition of pyrazolines can be depicted by the scheme
I
IV
COCHi
A This indicated that indeed @-addition4of phenyldiazoB methane to styrene had occurred to give 3,5-diphenyl1-pyrazoline (I, Ar = C6H5),although a small amount of what may be the 3,4-isomer I1 (Ar = C&) was isolated. I n order to test the generality of the reaction and of the decomposition, 3,5-bis-(p-chlorophenyl)-l-pyrazoline (I, Ar = P-ClC6H4) was prepared from p-chlorophenyldiazomethane and p-chlorostyrene. I t also underwent thermal decomposition with the sole formation of trans- 1,2-bis-(p-chlorophenyl)-cyclopropane. T h e addition of diazoalkanes t o olefins has been viewed as a cis addition5 and was shown t o be a stereoselective reaction. From steric considerations, it was assumed that the addition of the aryldiazomethanes to the styrenes had resulted in the formation of the trans1-pyrazolines (I). I t was subsequently shown that inolefins deed the 3,5-substituents were trans.6 , H The stereospecific decomposition of I t o the corresponding t runs-1,2-diarylcyclopropanes is t o be contrasted with the mixture of products formed from the trans cis thermal decomposition of 3,7-diphenyl-1,2-diaza-lcycloheptene' and of 3,8-diphenyl-1,2-diaza-l-cyclo- The stereospecific decomposition of the trans-3,5-diaryloctene.8 The base-catalyzed decomposition of 21-pyrazolines indicated that, a t least in the 3,5-diaryl pyrazolines a t high temperatures, though extensively compounds, the lack of stereospecificity of the cycloused for the synthesis of cyclopropanes, very often propanes resulting from the base-catalyzed decomposigives a mixture of the cis and trans isomers as well as tion of the corresponding 2-pyrazolines did not result the corresponding olefins. Rinehart and Van A ~ k e n ~ , during ~ the conversion of B to C (or B' to (2'). Since it have shown that, a t low temperatures, cis- and trans-3was shown that the cyclopropanes were stable under carbomethoxy-3,4-dimethyl1-pyrazolines gave the corthe conditions of the decomposition, the formation of responding cyclopropanes with very little formation of the mixture of cis- and trans-cyclopropanes must be olefin. Similar results were obtained by Swiss workers. lo due t o the nonstereoselective isomerization of the 2Van Auken and Rinehart4 have discussed the mechapyrazolines to the 1-pyrazolines (A + B and B'). A nism of the decomposition of 1-pyrazolines. ' The core of similar general conclusion was reached by Jones,13 althe problem seems to reside in the step during which though the results of Rinehart and Van Auken have stereospecificity may be retained or lost. Walborsky conclusively shown that such a general statement is not and Pitt" have recently questioned the validity of the always valid. Inspection of the scheme for the decomfree radical mechanism for the thermal decomposition position suggested a more generally applicable theory, of 1-pyrazolines. namely that the stereochemistry of the resulting cycloElectron spin resonance studies of the photolytic depropanes and the extent of olefin formation will be decomposition of I a t 77'K. in a Nujol or Fluorolube termined by the structure and the stability of the interhave indicated the presence of a free radical in mediate biradicals (C or C') a t the temperature of the each case (free spin value), No evidence was found for a decomposition. triplet state. This result seems consistent with the exThe nonstereospecific decomposition of the seven- and (1) T . V. Van Auken and K . 1- Rinehart, J . A m . Chem. Soc., 84, 3736 eight-membered ring azo compounds has been previ(1962) ously compared t o that of 3,5-diphenyl-l-pyrazoline(I, ( 5 ) R . Huisgen, H . Stangl, H . J. S t u r m , and H. Wagenhofer, Angew. Ar = C6H5). The rate of decomposition of I (Ar = C6&) C h e m , 78, 170 (1961). (6) C G . Overberger, J-P. Anselme, and J R. Hall, J . A m . Chem. Soc., a t 80' was 526 times faster than that of l-azo-bis-l8 6 , 2752 (1963). phenylpropane (see Table I ) . Models of the l-pyra(7) C . G . Overberger a n d J. G Lombardino, ibid, 80, 2317 (1958) zolines had indicated that the planar configuration of ( 8 ) C. G . Overberger and I . Tashlick, i b i d . , 81, 217 (1959). the five-membered azo ring induced a considerable (9) K L Rinehart a n d T . V Van Auken, ibid.,82, 525 (1960). (10) K Kocsis, P. D Ferrini, D . Arigoni, a n d 0 . Jeger, H e l v C h i m . Acta, amount of angle strain. This would weaken the C--N 48, 2178 (1960) bonds and furthermore, the planarity of the C -N=N(11) H M Walborsky and C. G. P i t t , J . A m . Chem. Soc., 84, 4831 C system in the ground state would greatly facilitate (1962)
1 ;qp,
(12) We wish t o thank Dr A M. Trorzolo of Bell Telephone C o f o r obtaining these spectra for us
I",?.
..
1
(13) W. M . Jones, J . A m . Chem. Soc., 82, 3136 (1960), and previous papers.
660
C. G. OVERBERGER AND JEAN-PIERRE ANSELME
Vol. 86
l-Acetyl-3,5-diphenyl-2-pyrazoline .-A solution of 0.14 g . (0.6 nimole) of 3,5-diphenyl-l-pyrazoline in 5 nil. of acetic anhydride and a catalytic amount of p-toluenesulfonic acid was stirred for 1 hr. a t room temperature. It was then heated for an additional hour with continued stirring. The excess acetic anhydride was removed by heating in vucuo. T o the residual brown oil was added 25 mi. of 3 : 1 ethanol-water mixture with heating. Upon cooling, there was obtained about 0.10 g . of cream-colored grains, m.p. 125-125.5°. This product was identical with the compound prepared b>- the reaction of 3,5-diphenyl-2-pyrazoline with acetic anhydride,l' mixture m . p . 125-128". The infrared spectra TABLE I were identical and had a strong carbonyl absorption a t 1650 C I I I . - ~ . trans-l,2-Diphenylcyclopropane.-A solution of 0.23 g . (1.O KINETICDATAOF CYCLICAzo COMPOUNDS mrnole) of 3,5-diphenyl-l-pyrazolinein 10 ml. of benzene was Energy heated under reflux until the evolution of nitrogen had stopped. of activ. The solvent was removed in vacuo and pure trans-1,2-diphenylKate constant Rel. E., kcal.1 cyclopropane was obtained as a colorless oil, n Z 3 D 1.5987 (?z*OD k sec -1, 80' rate mol? 1.5995j7 prepared by base-catalyzed decomposition of 3,5-diphenyl-2-pyrazoline). The n.m.r. spectrum was identical with 1-Azo-his-1-phenylpropane* 1 9 X 10-8 1 32.3 t h a t reported by Curtin, et al." 3,5-Diphen>I-1-pyrazoline 1 0 X 10-3 526 11.6 3,5-Bis-( p-chloropheny1)-1-pyrazoline .--A solution of p-chloro3,7-Diphen) I- 1,2-diaza-lphenyldiazomethane in ether was prepared in a manner similar t o cycloheptene' 4 3 x 10-4 268 29.7 t h a t described for phenyldiazomethane from 140.5 g. (1.O mole) of p-chlorobenzaldehyde and 64 g . (1.9 moles) of anhydrous 3,8- Diphenyl-1,2-diaza-1hydrazine. From this solution, by addition of 42.2 g. (0.30 cyclooctene8 3 5 x 10-8 0.02 36.7 mole) of p-chlorostyrene in 100 ml. of ether, was obtained after 1 day 24 g. (27%) of 3,5-bis-(p-chlorophenyl)-l-pyrazoline,11i.p. The base-catalyzed decomposition of 3,5bis-(p118-1 19" dec. Recrystallization from hot methanol gave colorchlorophenyl)-2-pyrazoline(111, Ar = p-C1CeH4) a t less needles, 1n.p. 120-121' dec. after drying in v ~ c u oover phos200' was reported to give trans-l,2-bis-(p-chlorophenyl)- phorus pentoxide. The ultraviolet spectrum had a single peak, 327 mp (emaX 680). The infrared spectrum had the characcyclopropane, m.p. S3-83.5'.14,15 There was no menteristic sharp medium band a t 1543 cm.-' (-N=X-).6 tion of the formation of the cis isomer. While i t is 4 n a l . Calcd. for C I j H ~ ~ C 1 ~ NC,2 :61.87; H , 4.29; Found: true t h a t the 1n.p. of the crude solid obtained from the C, 61.84; H , 4.26. deconiposition was about 80°, i t was found that, by l-Acetyl-3,5-bis-(p-chlorophenyl)-2-pyrazoline.--Asolution of careful work-up of the various filtrates (see Experi0.1 g. (0.3 mniole) of 3,5-bis-(p-chlorophenyl)-l-pyrazoline in 10 nil. of acetic anhydride and a catalytic amount of p-toluenesulmental section), the cis isomer was isolated as a low fonic acid was allowed to stand a t room temperature for 3 days. melting solid, m.p. 50-52'. The assignment of conThe slightly yellow solution was evaporated in z'acuo with heating figuration was confirmed by their n.m.r. spectra (see on a steam bath and the residue dissolved in ethanol, heated with Table 11). charcoal, filtered, and allowed to cool. The slightly browni:h crystals were recrystallized from ethanol; m.p. 108-109 , TABLE I1 identical with the product obtained from the reaction of 3,5-bis(p-chlorophenyl)-2-pyrazoline with acetic anhydride,I4 mixture S . M . R . DATAO F 1,2-DIARYLCYCLOPROPANESB m.p. 108-110". The infrared spectra were identical and had a -Aromatic protons-Benzylic protonsstrong carbonyl absorption a t 1650 cni.-'. cis lvans c-l cis lrans 6-1 trans-1,2-Bis-(p-chlorophenyl)-cyclopropane.-A solution of 0.468 g. ( 1 . 5 mnioles) of 3,5-bis-(p-chlorophenyl)-l-pyrazolinein 1,2-DiphenyIcyclo10 ml. of toluene was heated on the steam bath for 2 hr., after 7 . 5 5 7 . 8 7 -0.32 propaneb 3 . 0 4 2 . 8 7 0 17 which time the evolution of nitrogen had ceased. A practically 1,2-Bis-(p-chloroquantitative yield of trans-l,2-bis-( p-chloropheny1)-cyclopropane, phenyl)-cyclom.p. 83-83.5', was obtained after evaporation of the solvent. The n.ni.r. spectrum had a symmetrical quadruplet centered a t 2.76 propane 3.08 2.73 0.35 7.63 7.90 -0.27 T, a triplet centered a t 7.90 T, and a quadruplet a t 8.60 T and was D. Y. CurGiven in T-values and taken in CCI, a t 60 Mc. identical with the spectrum of the high melting isomer ( m . p . tin, d a l . , J . .4m. Chem. SOC.,83, 4838 (1961); 84, 863 (1962). 83-83.5'), obtained from the base-catalyzed decomposition of 3,5-bis-(p-chlorophenyl)-2-pyrazoline, mixture m.p. 83-83.5". Experimental l 6 Base-Catalyzed Decomposition of 3,5-Bis-( p-chloropheny1)-2pyrazoline. cis- and trans-l,2-Bis-( p-chloropheny1)-cyclopro3,5-Diphenyl-l-pyrazoline.-To525 nil. of an ether solution of pane.-The pyrazoline obtained from 17.5 g. (0.0633 mole) of phenyldiazoinethane, prepared by oxidation with 300 g. of mertrans-p,p'-dichlorobenzalacetophenoneand 10 nil. of anhydrous curic oxide of a n ether solution of benzalhydrazone (from 106 g. hydrazine was decomposed immediately after isolation by heating of bmzaldehyde and 66 g . of anhydrous hydrazine in 600 ml. of a t about 200" in the presence of a catalytic amount of powdered ether), was added over a period of 1 hr. 35 g . (0.336 mole) of potassium h y d r o ~ i d e . l ~ , T ~ h6 e crude pyrolysis product was taken styrene in 90 1111. of ether. Throughout the reaction the flask up in ether, the ether layer separated, washed successively with waq wrapped with a piece of aluniinum foil. The following day the water, a dilute solution of hydrochloric acid, finally with water reaction mixture remained red in color. About 200 nil. of the and dried over sodium sulfate. The solvent was removed under solvent was removed in '~lncuo. The flask then was immersed in vacuum and the resulting oil chilled. The m.p. of the crude an ice bath and the reaction mixture allowed to stir. The total product was about 80". Recrystallization of the product from reaction time vias 36 hr. After thorough cooling of the flask in a n ethanol gave pure t~ans-l,2-bis-(p-chlorophenyl)-cyclopropane, ice bath for 2 h r . , the precipitate was washed with ice-cold ether m.p. 83-83.5". The n.m.r. spectrum consisted of a symmetrical to remove the red color. The total yield of crude product after quadruplet centered a t 2.73 T (aromatic protons), a triplet at wrirk-up of the first and second filtrates was 17.7 g. (23.77@),m . p . 7.90 7 (benzylic protons), and a quadruplet a t 8.60 T . 107-109° dec. T w o recrystallizations from warm methanol, Concentration of the mother liquor from the tvans isomer gave followed by drying in aaruo over phosphorus pentoxide a t room a second crop of solid with a lower melting point. This process temperature, gave the pure product as shiny white flakes, m.p. was repeated five times t o give the pure ris-l,2-bis-(p-chloro109-110" dec. The ultraviolet spectrum had a single peak, phenyl)-cyclopropane, m.p. 50-52" (from ethanol-water). The XE'OH ,,,ix 329 IIIF (e,,,,, 291). The infrared spectrum was very similar n.1n.r. spectrum was similar t o that of the tvans isomer except to t h a t of 3.7-diphenyl-1.2-diaza-1-cycloheptene' and of 3,8for the position of the bands. I t had a symmetrical quadruplet diphenyl-1 , ~ - t l i n z ~ r - l - r ~ c l o ~ ~ showing c t e n e , ~a sharp medium band centered a t 3.08 T (aromatic protons), a triplet a t 7.63 T (benzylic a t 1548crn.-'fi (-X=S-). protons), and a quadruplet a t 8.67 T . .4niil. C:ilcd. for CliHlaSp: C, 81.05; H, 6.35. Found: Anal. Calcd. for C , ~ H I Z C I ? : ' C68.45; , H , 4.60. Found: C , 81.01; H , 6.28. C , 68.66; H , 4.78. Kinetics-Spcctro grade xylene was used as solvent for the ( 1 4 ) AI. H a m a d a , Boi3'7r Kn,eahu. 21, 22 (195G). decomposition and the rate constants were calculated from the (13) 1- Biro. M', Voetgli. and P. I,auger, Heis'. C h i m . Acta. S T , 2230 plots of nitrogen evolved against time. (19.54)
the decomposition. This was entirely borne out by the remarkably low activation energy for the decomposition. It was found t o be 11.6 kcal./mole compared t o that of the seven- and eight-membered ring azo compounds, 29.7 and 36.7 kcal./mole, respectively (see Table I ) . The low activation energy may also explain the stereospecificity observed during the decomposition to the cyclopropanes.
(18) T h e melting points are uncorrected. T h e n . m r. spectra were run in carhnn tetrachloride a t 60 Mc with tetramethylsilane as an internal sta,ndard
(17) D . Y . Curtin, el ai., J . A m . C h e m . S O L . ,83, 4838 (1961); 84, 863 (1 962)
Feb. 20, 1964
1,3-CYCLOHEXilNEDIOXES WITH HYDRAZINE
Acknowledgment.-We wish gratefully to acknowledge the support of this work by the National Science
[CONTRIBUTION FROM THE
DEPARTMENT OF
66 1
Foundation, Grant No. NSFG-17448, and the technical assistance of Mr. Ned Weinshenker.
CHEMISTRY, STATE UNIVERSITY O F IOWA,
IOWA CITY,
IOWA]
Reactions of 1,3-Cyclohexanediones with Hydrazine : A Novel Pyridazinopyridazine Synthesis as a Result of Oxidation Promoted by Steric Strain BY J. K. STILLEAND R. ERTZ’ RECEIVED SEPTEMBER 5, 1963 The reactions of 1,3-cyclohexanedione and 5,5-dimethyl-1,3-cpclohexanedione with excess hydrazine hydrate produce 1.4,5,8-bis-trimethylenepyridazino[4,5-d]pyridazine and 1,4,5,8-bis-P,@-dirnethyltrimethylenepyridazino[4,5-d]pyridazine, respectively. The mechanism of this reaction was demonstrated t o involve formation of the cyclic azine a n d subsequent air oxidation to the aromatic pyridazine structure. This reaction represents a novel method of pyridazine formation.
The reaction of 1,3-~yclohexanedionewith excess hydrazine hydrate has been reported2 to afford a product CsHeNz, whose structure was reported to be either 1,3-azo-1,3-cyclohexadiene(I) or its dimer 11. It is evident that I is an unlikely candidate for the CsH6N2 N=N
N=N I1
I
compound and the formation of I1 would involve azine formation, tautomerization, and finally oxidation of the hydrazo tautomer to the azo compound. Further, it is unusual that such a facile isomerization and oxidation in the formation of I1 would take place to the exclusion of cyclic azine formation, since the formation and isolation of cyclic azines from diketones are the usual modes of r e a ~ t i o n . ~Under certain conditions acetonylacetone reacts with hydrazine hydrate to form an associated dimer of a dimethyldihydropyridazine,4 but this is a special case of the reaction with diketones. The reaction of 1,3-~yclohexanedionewith hydrazine hydrate does indeed form a light yellow, crystalline compound, whose elemental analysis and molecular weight verified the Cl2H1,N, compound described earlier. The infrared spectrum of this compound failed to reveal the characteristic C=N or N=N stretching and only a weak maximum a t 1625 crn.-’, which could be ascribed to the C=C moiety, was observed. The ultraviolet spectrum confirmed the absence of N=N absorption and showed a complicated absorption spectrum in the 250-3 10 mp range. This spectral data and the n.m.r. spectrum established 1,4,5,8-bistrimethylenepyridazino [4,S-d]pyridazine (111, R = H) as the product of the reaction of 1,3-~yclohexanedionewith hydrazine hydrate. The N-N
“G=B R
N-N
111, R = H , CHJ
quintet centered a t 7.67 T (relative to tetramethylsilane) was assigned to the four internal methylene protons; ( 1 ) Abstracted in part from t h e P h . D Thesis of R . E r t z , February, 1964 (2) N . A. Domnin and N . S . Glebovskaya, Zh. Obsch. K h i m . , 27, 656 (1957). (3) C. G. Overberger, Record Chem. Progr., 21, 21 (1960). (4) C. G. Overberger, N. R . Byrd, and R. B. Mesrobiao, J . A m . Chem. Soc , 78, 1961 (1956).
the areas of the components of the quintet were the expected 1: 3 : 5 : 3 : 1. The triplet centered a t 6.6 7 was assigned to the eight equivalent methylene protons ; the areas of the components of the triplet approximated a 1 : 2: 1 ratio. The relative number of triplet to quintet protons was 2 : 1. Further support of the pyridazine structure (111, R = H) was gained by an investigation of the product of the reaction of 5,j-dimethyl- 1,3-cyclohexanedione with excess hydrazine hydrate. The infrared spectrum of this product showed no absorption assxiated with the C=N or N=N moiety. The ultraviolet spectrum failed to reveal the characteristic N=N absorption, but showed again a complicated absorption spectrum between 250 and 310 mp. This spectral data and the n.m.r. spectrum established 1,4,5,8-bis-P,P-dimethyltrimethylenepyridazino [4,5d]pyridazine (111, R = CH,) as the product of the reaction of 5,S-dimethyl1,3-cyclohexanedione with hydrazine hydrate. The singlet a t 8.83 T (relative to tetramethylsilane) was assigned t o the twelve methyl hydrogens and the singlet a t 6.72 T corresponded to the eight methylene hydrogens. The relative number of methyl protons to methylene protons was 3 : 2. The formation of I11 (R = H , CHJ presumably proceeds through the intermediate IV which contains two azine linkages, yet compounds containing two
RQFpR R
N-N IV, R = H , CHs
azine linkages formed in the condensation of acyclic diketones with hydrazine are stable enough to be isolated from the reaction mixture.3 This would indicate that the intermediate IV must have a special reactivity associated with it and is not stable under the conditions of the reaction. Models of IV show that the hydrogens on the two internal methylene groups are no greater than 1.2 A. apart, the van der Waals radius for hydrogen. Thus, because of the close proximity of the two internal methylene groups, IV, in the presence of an oxidizing agent, dehydrogenates with bond formation to produce the pyridazine 111, and thereby relieves the strain imposed. It is significant that cyclodecapentaene, which is forced into the same type of steric crowding, has never been isolated, although its transitory existence has been indicated.s Several examples of this type of oxidation involving bond formation to afford the same ring system have been described in the (5) M . Avram, C D. Nentizescu, and E hlarica, Ber , 90, 1857 (1957)
