5692
COMMUNICATIONS TO THE EDITOR
The differences in solvolytic reactivities would not be as large a t 400 or 500°, but one should find the same order of reactivity. One notes t h a t the reactivity of exo-norbornyl chloride is less than t h a t of cyclohexyl or cyclopentyl chloride, although an analogy to carbonium ion reactions in solution requires a greater reactivity. I n addition, the reactivity of a-phenylethyl chloride is comparable to t h a t of the other secondary chlorides. The analogy would predict a rate similar to t h a t of t-butyl chloride. Exner has recently suggested t h a t a parallelism of rates a t two different temperatures is sufficient to infer similarity or identity of mechanism in a reaction series.8 Inversion of reactivity due to inclusion of an isokinetic temperature in the experimental temperature rangeg is discounted. However, as one can see from Table I , isokinetic temperatures do intrude into the ordinary temperature range for thermal dehydrochlorination. The work reported herein shows clearly t h a t the "quasi-heterolytic" mechanismla for gas-phase thermal dehydrochlorination is not correct in detail, although the parallel reactivities to solvolytic reactions found previously now become more difficult to explain.
VOl. 86
above 190 mp. The presence of the -HC=CMegroup is indicated by the n . m . ~ -maxima .~ a t T 8.2
A. I
q C Q R
A
A
I1ROzC 3COzR
I11
ROzC
IV, R = H V, R = M e
VI, R = H VII, R = Sle
(intensity 3 ) and 4.5-5.0 (1) and confirmed by ozonolysis followed by hypobromite oxidation to the dicarboxylic acid IV (30%), m.p. 133'. This, with acetic anhydride, yielded the anhydride (m.p. 40-40.5') and with diazomethane, the ester (V) ; the infrared, ultraviolet, and n.m.r. spectra of these three compounds indicate the absence of olefinic groups, so that the acid IV is monocyclic. T h a t it is a glutaric acid Acknowledgment.-The support of the National is suggested by the maxima a t 1761 and 1805 ern.-' Science Foundation (Grant No. GP2-17) is greatly of the anhydride and confirmed by a reverse Michael appreciated. reaction.6 Thus, when the ester V was saponified ( 3 hr. refluxing with 10% potassium hydroxide in (8) 0 . Exner, Coiieclion Czech. Chem. Comm., 2 9 , I094 (1964). (9) J . E . Leffler, J . O i g . C h e m . , 20, 1202 ( l 9 5 , j ) . methanol) and the product re-esterified, gas chroma(IO) T o whom inquiries should be addressed a t Florida Atlantic Univertography indicated starting material (37.5%) and a new sity. isomer (VII, 5670). The same reaction was effected (11) National Defense Education Act Fellow. DEPARTMENT OF CHEMISTRY WILLIAMC. H E R N D O N ' ~ less cleanly by heating a 6y0solution of V in isooctane OF MISSISSIPPI JACKM . SULLIVAN for 20 hr. a t 280". The corresponding new acid (VI) UNIVERSITY USIVERSITY,MISSISSIPPI MELVINB. HEN LEU'^ had m.p. 156-157', Amax 206 mp ( t 15,000), and, when treated with ozone followed by warm 30y0 hydrogen DEPARTMEXT OF CHEMICAL AND JERALD M . MAN ION^^ PHYSICAL SCIENCES peroxide, gave isopropylsuccinic acid (45%), identiFLORIDA ATLANTICUNIVERSITY fied by infrared spectrum and mixture melting point 33432 BOCARATON,FLORIDA with a synthetic' specimen. RECEIVED JULY 6, 1964 The photoproduct I11 is thermally stable, having a half-life a t 300° of 40 min. ; five pyrolysis products, probably isomers of the starting material, are formed. When heated at 240' for 5 hr. with 5% platinized Synthesis of a Bicyclo[Z.l.l]hexene charcoal, m-cymene and p-cymene were obtained Sir: (8 and 5%, respectively, from a 96% sample); these The recent photoisomerization of 1,j-hexadiene to were isolated by gas chromatography and identified bicyclo [2.1.1]hexane' suggests a new general approach by their infrared spectra. Buchi and Goldmans to the synthesis of this interesting ring system.2 This have described the acid-catalyzed aromatization of communication records a cognate preparation of the another bicyclo[2.l.l]hexane. first unsaturated member (111) of the series. The mass spectrum of I11 further confirms the presence of an isopropyl group, having its base peak a t Ultraviolet irradiation of wphellandrene (I) was reported to give a mixture of trienes (11), which dismie = 93 and the complementary ion peak in comappeared on prolonged i r r a d i a t i ~ n . ~In the present parable abundance (58%) a t mle = 43.9 I t is thus work a 3yo ethereal solution of this terpene (Roy0)was surprising that the n.m.r. spectra of neither IV nor irradiated with light above 250 mp until i t showed no V show splitting of the isopropyl peak a t 7 8.9-9.1, absorption in this region. The crude product showed while those of the anhydride of IV and the hydroonly a weak maximum a t 1950 cm.-' due to allenic carbon I11 both show this peak as only partially rephotoproducts4 and yielded one principal photosolved doublets ( J = 3 and 1.6 c.P.s., respectively). product (35%) on distillation. ( 5 ) Kun in CDCln on a Varian A-60. T h e author is deeply indebted t o This compound (111) has b.p. 55" (18 mm.), is Drs. L. Stautzenberger a n d K . M. Geudin. Celanese C o r p . . Clal-kwood' Texas, for t h e n . m . r . a n d mass spectral d a t a given in this war-k optically inactive, and shows no ultraviolet maximum (I) K . Siinivasan, 3 P h y s . Chenr , 67, 1367 ( 1 0 6 3 ) : J . A m . C ~ P SI O~L.. , 8 6 , 819 (1963)
( 2 ) For a review see J. M e m w a l d , Record C h e m P Y O W ,2 2 , 39 (1961). ( 3 ) I < . J d e K o c k , S . G hlinaard. a n d E Havinga, R e c . ira7'. chrm.. 7 9 , 922 (1960) (4) k: J CI-owley, Pror. Chrin Soc., 1 7 (1064).
(6) C / . L Crombie, J . Crossley, a n d D . A. Mitchard. J . Chem Soc., 49.57 (1963). ( 7 ) P . A. S. S m i t h a n d J . P. Horowitz, J . A m . Chrm. S O L , 71, 3418 (1949). ( 8 ) G . Buchi a n d I. h l . Goldman, ibid., 79, 4741 (19.57). (9) R . I . Reed in " M a s s Spectrometry of Organic Ions," F. W. McLafferty. E d . , Academic Press, I n c . , 1963, p p . 656 el s e q .
Dec. 20, 1964
COMMUNICATIONS TO THE EDITOR
5693
latter a ketene fragment resulting from the familiar retro Diels-Alder-type of fragmentation (see arrows), common for alkaloids of the aspidospermine'O and (10) Satisfactuty caibon a n d hydrogen analyses were obtained for all new compound' refractine classes.11 The M - 42 fragment (m/e = DEPARTMENT OF CHEMISTRY KEVINJ CROWLEY 252) can then undergo simple bond fission as indicated ITSTITUTOVENEZOLANO DE to yield an ion of m/e = 109, a very characteristic ITVESTIGACIOTES CIENTIFICAS( I V I C ) phenomenon for systems such as 111. Other imCARACAS, \.ENEZUELA portant ions are the indole fragments of m/e = 130 RECEIVED SEPTEMBER 28, 1964 and 143, 144, as well as the one a t m/e = 138 which arises from the alicyclic part lria a variation1* of the Interconversion of the Aspidospermine Skeleton general pathway outlined above. Further proof of to the Refractine Type' the conversion of CH3CO- to -CHzCO- is derived from the base-catalyzed exchange of the a-hydrogens. Sir : Two atoms of deuterium were exchanged (under conI n the course of our work2 on the structure of ditions leading to incorporation of three deuterium minosine3 ( = minovincine4) I, an alkaloid isolated atoms into I) as judged from the mass spectrum of the from Vinca r n i n ~ r ,we ~ , ~discovered a reaction which product which also agrees with the above jnterpretamade possible an experimentally facile transformation tion of the spectrum of 111 (peaks a t m/e = 109, 130, of a skeleton of the aspidospermine type5 into the 140, 143, 144,252, and 296). pleiocarpine6-refractine' class of alkaloids, an interChemical transformations of I11 support the assignconversion of considerable biogenetic interest. ment : lithium aluminum hydride reduction produced While our approach as well as the conclusions rea dihydroindole alcohol I V (mol. wt. 296), the mass garding the structure of I had closely paralleled those spectrum of which had the expected peaks at m/e = published a t about that time by Janot, Djerassi, and 252 (M - 44), 140 ( = 138 2), and 109. Similarly, their collaborators, we realized that an unexpected reduction with lithium aluminum deuteride furnished cyclization had occurred during one of the degradation the C-20 deuterated derivative V, whose mass spectrum reactions. showed the appropriate shifts M = 297, m/e = 252 On heating of I in constant-boiling hydrochloric acid (M - 45), 141 ( = 138 3 ) , and 109. Partial exa crystalline compound (m.p. 176-177", mol. wt. 294) change of the active hydrogen on nitrogen in I11 for was obtained t o which we assign the hexacyclic strucdeuterium led to a compound (VI) which showed ture 111, a skeleton of the pleiocarpine type. Aside doublets in its mass spectrum a t m/e = 295, 294 ( M + ) , from its biogenetic significance, this observation con267, 266 (M - 28), 252, 253 (M - 42), 145, 144, and tradicts the report4 cited above in which the apparently identical substance (same melting point and molecular weight, also obtained by acid decarboxylation of I) was considered-without citing much experimental evidence-to be the isomeric indolenine 11, the product expected a priori in the hydrolysis of a carbomethoxyCOOCH3 methyleneindole such as I. I I1 The mass spectrum of the decarbomethoxylation product cannot be reconciled with structure I1 (it is 111, R i = H , R z = O very different from the one exhibited by the carbonylR2 IV,Ri=H,Rz=H,OH V, Ri = H, Rz = D,OH free analog of I P ) and all our results are consistent with structure TI1 instead : the ultraviolet spectrum is R1 21 *O typically that of a dihydroindole: ":A:: 241 ( e 7110) VI,Ri=D,RZ=O and 292 mp ( e 3080), and from the infrared absorpVII, R,=H,Rz=H,H m/e = 294 tion a t 1706 and 3350 cm. ketone and amino functions can be inferred. The molecular ion a t m/e = 294 in the mass spectrum of I11 confirms the loss of the ester function and all other peaks are readily interpreted in terms of the assumed structure: loss of both 28 and 42 mass units from the molecular ion, the former representing carbon monoxide and e t h ~ l e n e , the ~ The other portions of these spectra are in accord with the assigned structures.1°
+
+
4
(1) Paper X X I l I on t h e Application of Mass Spectrometry t o S t r u c t u r e Problems. F u r paper X X I I see K . Biemann, P.Bommer, A. L. Burlingame, and W. J. M c M u r r a y , J . A m . Chem. Soc., 86, 4624 (1964). (2) In collaboration with Dr. J , Mokrj. and his colleagues, Chemical I n s t i t u t e of Slovak Academy of Sciences, Bratislava, Czechoslovakia. (3) J . Mokrg, I . KompiB, L. Dubravkovd, and P. SeffoviC, Paper pre sented a t t h e Second International Symposium on t h e Chemistry of Natural Products, 1 9 6 2 , Prague, Czechoslovakia. (4) M . P l a t , J . Le Men, M - M J a n o t , H. Budzikiewicz, J. M. Wilson, L. J. D u r h a m . and C . Djerassi, Bull. S O L . chim. France, 2237 (1962). ( 5 ) J. F. D. Mills and S. C. N y b u r g , Telrahedron L e l l e r s , No. 11, 1 (1959). H. Conroy, P. R . Brook, and Y.Amiel, ibid.,4 (1959). (6) W. G . K u m p , D . J. Le Count. A. R. Battersby, and H. Schmid, Helv. C h i m A d a . 46, 8.54 (1962). (7) C . Djerassi, T. George, X. Finch, H. F. Lodish, H. Budzikiewicz, and B . Gilbert, J . A m . Chem. S o c , 84, 1499 (1962). (8) K . Biemann and G. Spiteller, ibid.. 84. 4878 (1962).
M - 42,m/e
= 252
,,'e = 138
m/e=
m/e=
130
109
m/e = 144
(9) In a 1: 1 ratio, as determined by high-resolution mass spectrometry.
(IO) K . Biemann, M. Spiteller-Friedmann, and G . Spiteller, . I .
Am.
Chem. Soc., 86, 631 (1YG3). (11) C. Djerassi, H. Budzikiewicz, R . J . Owellen, J . M . Wilson, U'. G. K u m p , 1). J . LeCount, A. R . Battersby, and H. Schmid. Helu. C h i m . Acla,
L6, 7 4 2 (191i3).
