J . Org. Chem., Vol. 40,No. 10, 1975 1483
Acid Catalyzed Tricycloundecane Rearrangements
Large Enhancement of Apparent Isomerization Rates in Endo vs. Exo Precursors for Trifluoromethanesulfonic Acid Catalyzed Tricycloundecane Rearrangements Naotake Takaishi, Yoshiaki Inamoto,' and Koji Aigami Industrial Research Laboratories, Kao Soap Company, Ltd., Wakayama 640-91, Japan
Eiji Osawa Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060, Japan Received November 4,1974 The rate of the trifluoromethanesulfonic acid catalyzed rearrangement of 2,3-endo-tetramethylenenorbornane (endo-I) and that of 6,7-endo-trimethylenebicyclo[3.2.l]octane(endo-2) were found to be lo4 times larger than thos,e of the corresponding exo isomers. 2,3-Trimethylenebicyclo[2.2.2]octane(3) was also as reactive as the endo compounds. 6,7-endo-Trimethylenebicyclo[3.2.l]octane(endo-2) was synthesized for the first time and the structure was established unambiguously by 13C NMR spectroscopy. Product analysis for the isomerizations of endo precursors revealed some new aspects of the tricycloundecane rearrangement which have never been seen so far in the studies of the reactions of exo isomers.
obtained by dichlorocarbene ring expansion13 of 5,6-endoSchleyer and his group1 demonstrated that the pathway trimethylenenorborn-2-ene (4),14was reduced with metallic of the adamantane rearrangement of either exo- or endosodium in liquid ammonia12 to 6,7-endo-trimethylenebicytrimethylenenorbornane, (exo- 10 or endo- 10) was such clo[3.2.l]oct-2-ene (6),which on catalytic hydrogenation that these reactants at first gave an equilibrium mixture over palladium on charcoal gave endo-2. It is interesting consisting of both isomers which then rearranged to adamantane via several steps. In contrast to this, no endo isomer (endo- 1 ) was detected in the rearrangement of 2,3-exotetramethylenenorbornane (exo-1).2-8The difference between the behavior of the Clo and the C11 tricyclic hydrocarbons may be ascribed to either (or both) of two reasons: either that the equilibrium is further shifted to the exo isomer in C11 than in Clo precursors, or that endo- 1 is so reactive that it is present in too low a concentration to be detected. Measurement of the equilibrium between endo- l 4 endo-2 and exo-1 in the presence of palladium on alumina catapc1* lystg showed that the absence of endo-1 during the rearHI, ]Pd, c rangement could not be accounted for by thermodynamic reasons. Fast disappearance of endo-1, if it is formed a t all, is a remaining possibility which explains its absence. This prompted us to examine the rate of the isomerization of endo- 1. Preparation and aluminum chloride catalyzed rearrangement of endo-1 was reported by Whiting.5 However, they did not find any difference between the reactivities of endo-1 and exo-1, nor make any kinetic measurements. I 6 c1 6,7-exo- Triniethylenebicyclo[3.2. lloctane ( e x o - 2 ) , to5 gether with 4-homoisotwistane (tricycl0[5.3.1.0~~~]undecane) (9)6-8Jo and homoadamantane, was discovered by us8 L{AIHp to be an intermediate in adamantane rearrangements of exo- 1 and 2,3-trimethylenebicyclo[2.2.2]octane(3).11 Here again, no 6,7-endo- trimethylenebicyclo[3.2.l]octane(endo2 ) was detected during the rearrangement, suggesting a high reactivity of endo-2. Since endo-2 has never been prepared before, an unequivocal synthesis had to be established before the kinetic measurement, Determination of the rate of the isomerization of these precursors was accomplished in refluxing methylene chloride solvent in the presence of trifluoromethanesulfonic acid, which was recently discovered by us8 to be a very ef8 7 fective catalyst for the rearrangement. The system is homogeneous and, therefore, particularly suitable for use as the medium for the rate measurement. Synthesis alf 6,7-endo-Trimethylenebicyclo[3.2.l]octane ( e n d o - 2 ) . A synthesis of endo-2 was achieved by the application of the method of De Selms and Comb.12 3,4Dichloro-6,7-emdo-trimethylenebicyclo[3.2.l]oct-2-ene (5), 9
1
1484
J.Org. Chem., Vol. 40, No. 10, 1975
Takaishi, Inamoto, Aigami, and Osawa
that sulfuric acid hydrolysis13 of 3-chloro-6,7-endo-trimethylenebicyclo[3.2.l]oct-2-ene(7)(obtainable by lithium aluminum hydride reduction of 5 ) did not give the hoped(8) but for 6,7-endo-trimethylenebicyclo[3.2.l]octan-3-one only tarry materials, whereas acid hydrolysis was successfully applicable to 3-chloro-6,7-exo-trimethylenebicyclo[3.2.l]oct-2-ene for the preparation of 6,7-exo-trimethylenebicycl0[3.2.l]octan-3-one,~ the exo isomer of 8. ‘endo-2 prepared in this way showed correct elemental analysis and a mass spectrum, and its total and off-resonance proton-decoupled I3C NMR spectral5 were consistent with the structure of endo-2. The compound was distinctively different from exo- 2 as indicated by the comparison of various spectral as well as physical properties. Kinetics. Rate measurements were made on endo- 1, exo- 1, endo-2, em-2, and 3. The disappearance of the reactants was followed approximately to 50%,during which five to eight determinations on the concentration of reactants were done by the use of VPC. Reactions of endo-1, exo-1, endo-2, and 3 proceeded with reasonable rates by using 1 molar equiv of trifluoromethanesulfonic acid, but exo-2 isomerized so slowly with this amount of the catalyst that the rate measurement was impracticable. Therefore the reaction of e m - 2 was run in the presence of 4 M catalyst. The rate of exo-1 was also measured under the same conditions, and the ratio kero-l/ kexo.z for 4 A4 catalyst was used to calculate kero-a for 1 M catalyst with the assumption of an equality between two relative rates. The treatment is justified by the fact that both hero-l and hero-z are proportional to the fifth power of the catalyst concentration taken within the range from 0.4 to 6.0 molar equiv. All the reactants showed fairly good first-order kinetics when followed by VPC. The calculated rate constants and relative rates are listed in Chart I.
Chart I
elndo-2 4.1 x io4 2 x 104
endo-1
106 k, min-’
Re1 rate
4.6 X1@ 3x10’
A
5.8X ld4
exb-1 6.9 X lo1
4 x ioi4
4 X 10‘
3
1016k, min”
Re1 rpte
exo-2
IO6 k , mini'
Re1 rpite
1.9 1
encio-40 (l7.7 X103)
~1 x io3)
As is evident from these results, an interesting difference was discovered between the reactivities of endo and exo isomers. Rate constants for endo isomers are about lo4 times larger than those of the corresponding exo isomers. Compound 3, where endo and exo isomers are identical, reacted a t a similar rate to those of endo-1 and endo-2. Rate enhancement of one of the epimers vs. the other is rather familiar, e.g., in solvolysis reactions, but the phenomenon does not seem to have been recognized in the adamantane rearrangement of hydrocarbons. Product analysis (Table I) for the rearrangement of endo- 1 revealed another interesting feature of the reaction: no exo-1 was detected throughout the reaction. An interpretation of this may be that in endo- 1 the Wagner-Meerwein rearrangement to exo- 1 would occur much more slowly than the pathway leading to 4-homoisotwistane (9). The direct measurement of the rates of the interconversions between endo- l and exo- l is obviously impossible, since the reaction of endo- 1 does not give rise to any exo- 1 at all, and vice versa. Therefore the rate of the isomerization of 2,3endo-trimethylenenorbornane (endo-10) to its exo isomer (exo- 10) was measured in order to have a rough idea about the rate of the Wagner-Meerwein rearrangement of the bicyclo[2.2.l]heptane system under the present reaction conditions. The first-order rate constant for endo- 10 was found to be lo2 times smaller than that for the isomerization of endo- 1 (Chart I). Products. Golay (capillary) column VPC was used to determine the product compositions. Product analysis was done at appropriate stages of the rearrangements to establish time-conversion relationships. Identification of each product was made on a mass spectrometer connected to the Golay VPC instrument. endo-1 and endo-2 isomerized to the products listed in Table I. The combined yields of the products were almost quantitative, as was the case for other tricycloundecane precursors so far studied (exo- 1, exo-2,3, and 9).s Although the structure of seven products designated by letters A-E16 still remained unknown, they were all tricycloundecanes as determined by mass and l H NMR spectroscopy. Thus the reaction under study was really a rearrangement without being accompanied by any appreciable disproportionations and decompositions. All the endo reactants including 3 was found to give none of homoadamantane and methyladamantanes. The result is easily understood if we consider that these products are formed from 9.S Indeed 9 was quite unreactive in the presence of only 1 molar equiv of the catalyst, and gave none of homoadamantane and methyladamantanes in short reaction time (run 61) during which extensive reaction of endo compounds had been effected (runs 1-4 and 31-33). Unknown A was not found in earlier stages of the reaction of any precursors, while it was detected in longer reaction of every reactant and also of 9. Unknown B3 arose only in the reaction of endo- 1 and exo- 1 (runs 1-5 and 11,Table I). Considerable amount of Bz was formed in the reaction of endo-1 and exo-1 (runs 1-5, 11, and 21-23), although a little was formed in the case of exo-2,3, and 9 on prolonged reaction. B1 presented itself in the reaction of all the reactants including 9. It may be noted that B1 did not appear a t the early stage of the reaction of endo- 1, exo- 1, and endo-2 (runs 1-4, 11, and 31), whereas it did in the reaction of 3 from the beginning (run 51). No exo-2 was obtained at all at early stages of the reaction of endo-1 (runs 1-4), but a little was formed from endo-2 and 3 from the beginning (runs 31,32, and 51). Unknown D was always accompanied by 9, which suggested that D arose from and was in equilibrium with 9. Unknown
J. Org. Chem., Vol. 40, No. 10,1975
Acid Catalyzed Tricycloundecane Rearrangements
1485
Table I Products of Tricycloundecane Rearrangements under Trifluoromethanesulfonic Acid Catalysisa Productd yield, %e Reactant
Reaction
(amt of catalyst)b
time, hr (min)c
1 2 3 4 5
endo-1 (1.0)
11
exo-I (1.0)
(1) (2) (4) (17) 2 24
21 22 23 31 32 33 41 42 43 51 52 61
exo-1
1
(4.0)
24 48 (10) 1 8 1 8 38 1 24 6
Run
A
1-Me-Ad
B1
B2
63
C
4.0 8.8 15.4 15.5 14.3 1.5
3.5 6.2 8.2 7.7 6.8 0.3
2.8 4.8 5.6 5.9 5.9 1.0
2-Me-Ad
em-2
9
D
21.8 42.1 59.4 58.1 57.8 10.4
2.1 4.7 5.1 5.0 5.0 1.5
52.6 35.2 29.5 40.2 58.1 80.4 11.8 23.1 26.6 29.2 46.9 80.5
4.2 4.9 4.3 1.8 3.4 4.5
2.0 1.3 1.8
3.1 2.0 21.5 3.2 4.3
1.4 1.5
E
Homoad
~~
endo-2 (1.0) exo-2
(4.0) 3 (1.0) 9 (1.0) 9 (4.0)
1.5 1.2 6.1 8.0
0.3 0.5 3.5 9.2
8.4 11.9 11.0
10.9 7.0 5.1
2.2 1.8
2.2 10.0
0.8 1.1
2.2
1.6
0.2 1.3 1.8 9.1 12.6 2.8 17.6 1.1
1.0
1.7
13.2 15.6 14.1 0.5 1.1 4.2 1.9 8.9 11.9 5.0 16.6 8.1
0.6 6.0 8.4
3.4 11.6 2.4
1.0 6.8 5.0 0.6 0.7 0.8 84.4 45.6 18.8 1.5 5.4 0.3
0.3 0.3
20.2 2.2
71 1 19.6 4.1 0.5 1.6 9.3 1.0 3.2 51.8 4.5 2.3 6.2 18.9 4.6 41.1 72 6 1.0 4.4 14.4 1.3 3.6 2.6 1.6 16.8 5.8 6.5 24 2.4 5.3 18.0 73 36.3 2.8 1.8 20.3 11.6 8.0 100 10.0 0.9 25.2 5.5 74 15.0 1.3 1.2 a Reactant (200 mg, 1.33 mmol) and CF3S03H (200 mg, 1.33 mmol, or 800 mg, 5.33 mmol) in refluxing CHzClz (10 ml). In molar equivalents to the reactant. c Reaction time in parentheses is expressed in minutes. d Combined yields of the products were always almost quantitative, the balance being unreacted starting materials. Products are aligned in the order of increasing retention times. Abbreviations: A-E refer to compounds of unknown structure;8916 1-Me-Ad and 2-Me-Ad, 1- and 2-methyladamantane, respectively; Homoad, homoadamantane. e Calculated from VPC peak areas.
E was detectable only a t early stages of the reaction of 3 (run 51). This, coupled with the formation of an unusually large amount of D, was takens as an evidence for the pathway from 3 to E to D to 9. exo- 10 was the only product from endo- 10. Neither adamantane nor any other intermediated were detectable under the present reaction conditions. Discussion
It is shown in this work that endo precursors isomerize with much greater apparent rates than those of exo isomers. Adamantane rearrangements of polycyclic hydrocarbons consist of a very complex network of hydride transfer and isomerization reactions that occur competitively and c o n s e ~ u t i v e l y . ~The J ~ distribution of intermediates is controlled not only kinetically but also thermodynamically. It is quite difficult, therefore, to decide to which elementary reaction the observed rate enhancement should be ascribed. Some speculations, however, may be made concerning the process of the rate enhancement. The first and a t the same time rate-determining step in the adamantane rearrangement of endo- 10 or exo- 10 is, according to Schleyer,l hydride abstraction a t a tertiary carbon atom and 1,2-alkyl shift to 1,7-trimethylenenorbornane.If a similar scheme applies to 2,3-tetramethylenenorbornanes(l), abstraction of 2-ex0 hydride in endo-1 might be accompanied by the participation of the 6-methylene group. This same process should be unfavorable for the 2-endo hydride. Thus 6methylene participation in endo- 1 may lead to the formation of the bridged ion18 that lowers the activation energy.
Similar mechanisms involving the abstraction of angular exo hydride with neighboring methylene participation in endo-2 and 3 may account for the high reactivities of these compounds. Alternatively, the difference between the ground-state energies of endo and exo isomers may be a predominating factor that determines the activation energy difference. No definite interpretation of the phenomenon can be made at the present. Examination of the change in product distributions with reaction time in endo precursors clarified a more precise rearrangement scheme (Chart 11) than that in exo reactants C h a r t I1 enkdo-1 eixb-I
did.8 A conclusion in the previous studies6-sJ0 that 9 was a table,^ common intermediate to methyladamantanes from a various kind of precursor was further confirmed here. As is summarized in Chart 11,endo- 1first isomerizes to Bz, B3, and C. Of these three, only B3 is irreversibly isomerized to 9, while Bz and C are in equilibrium with 9, because these
1486
J. Org. Chem., Vol. 40, No. 10, 1975
two arose from other precursors o n prolonged reaction (runs 42, 43, a n d 52) and also from 9 (runs 71-74). It seems certain that there is n o direct route from endo- 1 to A and B1 (cf. r u n 51, since they were obtainable also in the reaction of various precursors as well as of 9 and, therefore, m u s t arise from 9. Immediate isomerization products from exo- 1 are Bz, BB, a n d C (run ll),t h e same as from endo-1. Interconversion between e n d o - 1 and e x o - 1 was not realized starting from either isomer side under the present reaction conditions. In view of t h e rate of the Wagner-Meerwein rearrangement of endo-10, conversion of e n d o - 1 t o exo-1 would be much slower than isomerization of endo- 1 to unknown B's and C (cf. C h a r t I). On t h e other hand, a n y endo-1, if ever formed from exo- 1, must react very fast compared to its formation. No intermediate was detectable in t h e rearrangement of either e n d o - 2 or exo-2 t o 9. T h e result for e n d o - 2 , together with t h e highest yield of 9 (80.4%), might suggest a somewhat selective pathway from e n d o - 2 to 9. T h e large proportion of B1 a n d C in the rearrangement of exo-2 (runs 42 a n d 43) is evidently a consequence of the long reaction time required for t h e compound. It can also be taken as a confirmation of the scheme that B1 a n d C are formed from and in equilibrium with 9. Hydrocarbon 3 was found t o give B1, together with E, as a primary product of isomerization. T h u s , contrary to our former view,s the isomerization of 3 consisted of at least two competitive reaction pathways. Formation of a little exo-2 from e n d o - 2 (0.6%, r u n 31) and 3 (1.5%,r u n 51) may be noteworthy. The amounts are considered too large to be formed only from 9 in t h e short reaction times (cf. run 61). Therefore the result may suggest direct formation of exo-2 from e n d o - 2 a n d 3 in spite of t h e former conclusion: based on t h e rearrangement of 3, that exo-2 was formed only from 9. Indeed these three compounds have closely related structures which could be interconverted via WagnerMeerwein rearrangement with assisted ionization.lg Unknown A was not formed directly from any of the fast-reacting precursors (runs 1-4, 31, 32, a n d 51). The stable intermediate 9 seems t o be a n immediate precursor to A, a n d this could not be disclosed in the previous study of slow-reacting compounds.s It would be appropriate here to mention the aluminum chloride catalysis results of Petrov4 a n d Whiting,5 which relate to the rate differences found in this work. Petrov4 obtained similar rates of rearrangement for exo- 1 a n d 6,7trimethylenebicyclo[3.2.l]octane ( 2 ) of unspecified configuration,8 a n d Whiting5 noticed that endo-1 and exo-1 behaved indistinguishably. The discrepancy between their results a n d ours is only superficial, and can be easily explained, because they measured the r a t e of formation of methyladamantanes. Under t h e drastic reaction conditions they applied, rearrangement of precursors t o 9 is very quick. Thus they determined the rate of t h e conversion of 9 t o methyladamantanes, that led t h e m to find the same isomerization rate for all t h e various reactants. Experimental Section All melting and boiling points are uncorrected. Instruments for the measurements of spectra and for conventional as well as capillary column VPC were the same as were used in the previous work.8 Deuteriochloroform was used as the solvent for NMR spectroscopy. Chemical shifts are reported in 6 for protons and in parts per million downfield from the internal MerSi standard for I3C nuclei. All the ir spectra were taken on neat samples. Trifluoromethanesulfonic acid was a commercial product of 3M Co. Methylene chloride *as dried over anhydrous calcium chloride and distilled immediately before use. 2,3-endo-Tetramethylenenorbornane(endo-1) was prepared according to Whiting5 from cyclopentadiene and p-benzoquinone
Takaishi, Inamoto, Aigami, and Osawa through Diels-Alder addition and subsequent hydrogenation and Wolff-Kishner reduction, and was freed from contaminating exo- 1 by purification by preparative VPC. 6,7-exo-Trimethylenebicy. clo[3.2.l]octane (exo-218and 2,3-trimethylenebicyclo[2.2.2]octane(318," were synthesized in the previous work. 3,4-Dichloro-6,7-endo-trimethylenebicyclo[3.2.lIoct-2-ene (5). To a solution of 33.5 g (0.25 mol) of 5,6-endo-trimethylenenorborn-2-ene14in 200 ml of petroleum ether was added 54 g (1.0 mol) of sodium methoxide. Ethyl trichloroacetate (153 g, 0.8 mol) was added dropwise to the above mixture with stirring in a period of 4 hr while the reaction mixture was kept below 0" by being immersed into an ice-salt bath. The reaction mixture was stirred for a further 2 hr at Oo, and then allowed to warm up t o ambient temperature, where it was kept overnight with continuous stirring. The mixture was poured onto 250 g of cracked ice-water, the separated aqueous layer being extracted four times with each 60 ml of ether. The aqueous layer was then made weakly acidic with the addition of 10% hydrochloric acid, and again extracted twice with each 60 ml of ether. The combined organic layer and ether extracts were washed with a saturated sodium chloride solution and dried over anhydrous sodium sulfate. Fractional distillation of the solution gave 41.9 g (77% yield) of 5: bp 123-124' (2 mm); n22.5D 1.5447; ir 2950,2870,1630, 1445,1335, 1055,960,773,718 cm-l; lH NMR 6 1.0-3.0 (complex m, 12), 4.37 (d, 1,J = 3.0 Hz, CHCI), 6.05 (d, 1, J = 7.0 Hz, C=CH); mass spectrum m / e (re1 intensity) 218 (61, 216 (9), 181 (17), 115 (17), 114 (lo), 113 (45), 112 (14), 79 (ll), 77 (32),69 (100),68(18), 67 (23), 41 (12). Anal. Calcd for CllH14C12: C, 60.85; H, 6.50; C1, 32.65. Found: C, 61.10; H, 6.34; C1,32.13. 6,7-endo-Trimethylenebicyclo[3.2.1 Joct-2-ene (6). Freshly cut sodium (35.4 g, 1.54 g-atoms) was added during a period of 30 rnin t o 300 ml of liquid ammonia cooled in a Dry Ice-acetone bath, and the reaction mixture was stirred for a further 30 min at about -50". A solution of 17.4 g (0.08 mol) of 5 in 50 ml of dry ether was added dropwise to the above mixture under efficient stirring in 35 rnin while the temperature was kept below -50°, stirring being continued for a further 30 rnin after the addition. Dry ether (300 ml) was dropped into the reaction mixture without external cooling, while ammonia was allowed to evaporate. To the residue were added carefully a methanol-ether mixture and then methanol to decompose any unreacted sodium. The reaction mixture was poured onto 11. of cold water, and the organic layer was separated. The aqueous layer was extracted twice with 200-ml portions of ether. The combined organic layer and ether extracts were washed with a saturated sodium chloride solution, dried over anhydrous sodium sulfate, and fractionally distilled under diminished pressure t o give 4.54 g (38%yield) of 6: bp 76O (5 mm); nZ25D1.5093; ir 3040, 3020, 2920, 2850, 2830, 2670, 1720, 1640, 1470, 1440, 1390, 1290, 1000, 935, 895, 755, 690 cm-l; 'H NMR 6 1.0-2.92 (complex m, 14), 5.24-5.98 (complex m, 2); mass spectrum m/e (re1 intensity) 148 (27, M+), 94 (16), 91 (15), 81 (ll),80 (401, 79 (loo), 78 (72), 77 (12), 67 (14), 66 (11). Anal. Calcd for CllH16: C, 89.12; H, 10.88. FOUND: C, 88.89; H, 11.01. 6,7-endo-Trimethylenebicyclo[3.2.1]octane (endo-2). In a 100-ml autoclave were placed 3.1 g (0.012 mol) of 6,40ml of ether, and 90 mg of palladium on charcoal catalyst (containing 5% palladium). Hydrogen was charged at an initial pressure of 6 kg/cm2, and the reaction mixture was shaken for 1 hr at ambient temperature. The catalyst was filtered off from the reaction mixture, and the filtrate was concentrated to give 3.0 g (95% yield) of crude endo-2 (95% purity). Fractionation by preparative VPC gave a pure sample: mp 41-42O (in sealed tube); ir 2950, 2900, 2840, 2660, 1460, 1450, 1440,1320, 1300,1270, 1230,1200, 1070,1040,960,890, 870, 850, 770, 720, 660 cm-l; lH NMR 6 1.1-2.2 (complex m, 16), 2.3-2.8 (complex m, 2); I3C NMR (multiplicity, re1 intensity) 18.7 (t, I), 24.9 (t,2), 28.2 (t, 2), 32.3 (t, l), 35.7 (d, 21, 45.1 (t,I), 47.5 (d, 2); mass spectrum m/e (re1 intensity) 150 (100, M+), 108 (30), 93 (25), 82 (go), 81 (40),80 (28), 79 (32),67 (81). Anal. Calcd for C11H18: C, 87.92; H, 12.08. Found: C, 87.84; H, 12.19. 3-Chloro-6,7-endo-trimethylenebicyclo[3.2.l]oct-2-ene (7). A solution of 20.6 g (0.095 mol) of 5 in 20 ml of tetrahydrofuran was added dropwise with efficient stirring to a suspension of 6.45 g (0.17 mol) of powdered lithium aluminum hydride in 150 ml of ether and 450 ml of tetrahydrofuran, the addition being so regulated that a gentle reflux was maintained. It took 20 min for the addition, after which the reaction mixture was heated under reflux for 24 hr. Unreacted lithium aluminum hydride was decomposed by wet ether, and the resulting mixture was poured onto ice water.
J. Org. Chem., Vol. 40, No. 10,1975
Acid Catalyzed Tricycloundecane Rearrangements The organic layer was separated and the aqueous layer was acidified with 10% hydrochloric acid. The aqueous layer was extracted five times with 100-ml portions of ether. The combined organic layer and ether extracts were washed three times with a saturated sodium chloride solution and dried over anhydrous sodium sulfate. Fractional distillation of the solution gave 10.6 g (61% yield) of 7: bp 67O (0.4 mm); n215D 1.5286; ir 3040, 2940, 2860, 1640, 1470, 1450, 1440, 1430, 1350, 1330, 1260, 1210, 1040, 960, 850, 680, 670 cm-'; 'H NMR 1.2-2.83 (complex m, 14), 5.83 (d, 1, J = 7.0 Hz, CIC=CH); mass spectrum m/e (re1 intensity) 184 (ll),183 (4), 182 (31), 147 (201, 115 (351, 114 (471, 113 (loo), 112 (96), 94 (Id), 91 (21), 79 (57), 78 (h2), 77 (43), 69 (27), 67 (26), 41 (18). Anal. Calcd for C11H15Cl: C, 72.32; H, 8.28; C1, 19.40. Found: C, 72.09; H, 8.04; C1, 19.19. Acid Hydrolysis of 3-Chloro-G,7-endo-trimethylenebicycl0[3.2.l]oct-2-ene (7). 7 (3.7 g, 0.02 mol) was mixed with 50 ml of 98% sulfuric acid cooled in an ice bath, and the mixture was stirred at ambient temperature overnight. The reaction mixture was poured onto cracked ice and extracted three times with 100-ml portions of ether. The ether extracts were washed three times with cold water and dried over anhydrous sodium sulfate. After evaporation of ether, the residue was subjected to distillation, which caused the contents of the distillation flask to suddenly polymerize a t about 90°. Ether extract of the polymerized mass gave a little (ca. 0.5 g) organic material of which 6,7-exo-trimethylenebicyclo[3.2.l]octan-3-one8 was the only volatile compound detected by VPC. Rearrangements of Tricycloundecanes. Kinetic Measurement a n d Product Analysis. Rearrangement reactions were run in the same equipment as was used in the previous study.s Aliquots taken out of the reaction mixtures were quenched by cold water, and the methylene chloride layers were analyzed on the Golay column VPC. In kinetic measurements, each reaction was followed up to about 50% completion, during which five to eight determinations of the concentration of the reactants were made. At least three repetitions were done for each reactant. First-order rate constants were calculated from these kinetic data, and the reproducibility of the rate constants within a run as well as among repeated runs was fairly good, with standard deviations of f1015% of the respective arithmetic mean. Identification of products with known structure was made by comparison of VPC retention times and mass spectra with those of authentic samples. Identities of unknown compounds originated from different precursors were established also by Golay GC-MS.
Acknowledgment. We thank Professor P. v. R. Schleyer for helpful discussions. Registry No. -endo-1, 54676-30-1; exo-1, 32789-29-0; endo-2, 54676-38-9; exo-2, 53495-28-6; 3, 38255-97-9; 4, 10466-50-9; 5, 54643-92-4; 6, 54643-93-5; 7, 54643-94-6; 9, 43000-53-9; ethyl trichloroacetate, 515-84-4;trifluoromethanesulfonic acid, 1493-13-6.
References and Notes (1)E. M. Engler, M. Farcasiu, A. Sevin, J. M. Cense, and P. v. R. Schleyer, J. Am. Chem. Soc.. 95,5769 (1973).
1487
(2)(a) P. v. R. Schieyer and R. D. Nicholas, Tetrahedron Lett., 305 (1961): (b) K. R. Blanchard, Ph.D. Thesis, Princeton University, 1966. (3)M. A. McKervey, D. Grant, and H. Hamiii, Tetrahedron Lett., 1975 (1970);D. E. Johnston, M. A. McKervey, and J. J. Rooney, J. Am. 93,2798 (1971). Chem. SOC., (4)N. S. Vorobeva, 0. A. Arefev, V. I. Epshev, and A. A. Petrov, Neftekhimiya, 11, 163 (1971). (5)J. A. Bone, J. R. Pritt. and M. C. Whiting, J. Chem. SOC., Perkin Trans. 1, 2644 (1972):C. Swithenbank and M. C. Whiting, J. Chem. SOC.,4573 (1963). - -, (6) N. Takaishi, Y. Inamoto, and K. Aigami, Chem. Lett., 1185 (1973). (7)M. Farcasiu. K. R. Blanchard, E. M. Engler, and P. v. R. Schleyer, Chem. Lett., 1189 (1973). (8) N. Takaishi, Y. inamoto,and K. Aigami. J. Org. Chem., 40,276 (1975). (9)Y. lnamoto and T. Kadono, Japanese Patent 78,155/73(1973);Chem. Abstr., 80,70449d (1974). (IO)K. M. Majerski and 2. Majerski, Tetrahedron Lett., 4915 (1973):A. Krantz and C. Y. Lin, Chem. Commun., 1287 (1971);J. Am. Chem. SOC.,95,5662 (1973). (11) N. Takaishi, Y. Inamoto, K. Aigami, K. Tsuchihashi, and H. ikeda, Syn. Commun., 4,225 (1974). (12)R. C. De Selms and C. M. Comb, J. Org. Chem., 28,2206 (1963). (13)C. W. Jefford, J. Gunsher, D. T. Hill, P. Brun, J. Le Gras, and B. Waegell, Org. Synth., 51, 60 (1971). (14)S.J. Cristol, W. K. Seifert,and S. B. Soloway, J. Am. Chem. Soc., 82, 2351 (1960). (15)Consisting of seven absorptions [t (re1 intensity, l),t (2), t (2),t (I),d (2), t (I), and d (211.The spectrum is also consistent with unknown 2,4-exo\
and -endoethanobicyclo[3.2.l]nonane (0x0-11 and endo-11, respec-
ewo.11
endo-11
tively). However, exo-11 was synthesized recently by us from 2-endohydroxymethyi-2,3-exo-trimethylenenorbornane through a ring expansion-hydride transfer reduction, and found to be different from endo-2: N . Takaishi, Y . Inamoto, and K. Aigami, J. Chem. SOC.,Perkin Trans. 1, in press. Ketones with the skeleton of 11 were prepared recently via an independent route: R . Schmid and H. Schmid, Helv. Chim. Acta, 57, 1883 (1974). (16)Actually A and C are not single tricycloundecanes but mixtures, while 61, B2, 63, D, and E are individual isomers no longer separable on the capillary VPC columns used. Letters A-E were originally assigned to unidentified fractions separated on conventional VPC columns. Fractions A , B, and C were later found further separable into three, three, and four components, respectively, on Golay columns. Since the roles of each compound in A and C in the rearrangement reactions have been left unclarified, we refrain from referring to these components in the text more precisely than by A and C in order to avoid unnecessary complications in the statement of the results. (17)H. W. Whitlock, Jr. and M. W. Siefken. J. Am. Chem. SOC.,90, 4929 (1968). (18)J. A. Berson, R. G. Bergman, J. H. Hammond, and A. W. McRowe, J. Am. Chem. SOC., 87, 3246 (1965);A. M. T. Finch, Jr. and W. R. Vaughan, hid., 5520 (1965);G. D. Sargent in "Carbonium ions", Vol. 111, G. A. Oiah and P. v . R . Schieyer, Ed., Wiiey-interscience,New York, N.Y., 1972,p 1132.For the contradictory evidence, however, see p 1161;H. Goering and K. Humski, J. Am. Chem. SOC.,90, 6213 (1968);H. L. Goering, C. Brown, and C. B. Schwene, ibid., 90, 6214 (1968);H. C. Brown and M.-H. Rei, ibid., 90,6216 (1968). (19)H. L. Goering and M. F. Sloan, J. Am. Chem. SOC.,83, 1992 (1961).
