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The Bishomoconjuga tive Rearrangement Pathway . Structural Bond Relocation Attending the Dehydrohalogenation of Unsaturated Cyclic a-Halo Ketones and Sulfones1,2 Leo A. Paquette,* Robert H. Meisinger, and Robert E. Wingard, Jr.3
Contribution from the Department of Chemistry, The Ohio State University, Columbus, Ohio 43210. Received October 31, 1972 Abstract: Reaction of 7-bromo-cis-bicyclo[4.3.0]nona-2,4-dien-8-one (la) as well as its 1,6-dimethyl (lb) and 1,6tetramethylene derivatives (2) with potassium tert-butoxide in dimethyl sulfoxide for short periods of time at 25 O results in dehydrobromination with structural bond reorganization to give bicyclo[4.2.l]nona-2,4,7-trien-9-ones (19, 21, and 26). Direct irradiation of these bridged ketones causes decarbonylation and cyclooctatetraenes are produced. When these molecules experience triplet sensitization, photoisomerization to barbaralones operates. 7-Chloro-S-thiabicyclo[4.3.0]nona-2,4-diene 8,s-dioxides rearrange in analogous fashion when treated with strong base in a polar aprotic solvent. The resulting bridged sulfones (34, 38, and 43) can be made to extrude sulfur dioxide by thermal or photochemical methods. These striking and unprecedented reactions provide a useful synthetic entry to functionalized [4.2.1]bicyclics. It is suggested that the a-halo ketones behave as in analogous Favorskii situations by deprotonation and subsequent rr-assisted C-Br ionization to give a dipolar ion which undergoes intramolecular cycloaddition to the proximate diene system. The a-chloro sulfones probably experience 1,3displacement of chloride ion with intermediate episulfone formation. The highly strained nature of these species and the DMSO solvent are believed to promote C-C bond heterolysis to afford a zwitterion with a chemical reactivity comparable to that seen for the oxyallyls.
A
common process of fundamental importance to the Br/CI leaving group effects are likewise noted,g but the chemistry of a-halo ketones and sulfones is their positive p value and the accelerating effect of substitrearrangement in the presence of strong base (the uents which enhance positive charge at the C-X carbon Favorskii4 and Ramberg-Backlund reactions,5 respecatom require that C-C bond formation be quite extentively). Recent investigations have established that sive. These data provide strong evidence for direct the mechanism of the Favorskii reaction involves initial rate-controlling internal halide displacement by the reversible enolate anion formations6 Subsequent exneighboring a-sulfonyl carbanion with formation of intermediate episulfones.5 tensive stretching of the C-X bond leads to a highly Although dipolar intermediates do not intervene in ionic rate-determining transition state as revealed by the Ramberg-Backlund rearrangement, it has been relatively large Br/C1 rate ratios,’ appreciable salt and recognized that subsequent carbon-carbon bond cleavsolvent effects,* and the highly negative p’s observed ~* the ejection of halide for loss of halide i ~ n . ~However, age of episulfones to generate such zwitterions can be is seemingly not the result of intramolecular s N 2 displacemade to operate in certain cases where strain factors gain importance. lo That such dissociations should be ment; actually, electron-withdrawing substituents atenergetically realizable is supported by the experimentached to the carbon atom of the C-X bond retard tally determine$ C-C bond length in cis-2-butene epithe rearrangement rate, whereas electron-donating subsulfone (1.60 A) which is exceedingly long” and the stituents have the reverse effect.’ Rather, a substantial facility with which suitably constructed episulfones body of data supports the concept that C-X ionization undergo kinetically controlled C-C bond rupture under assisted by x participation from the proximate enolate anion function leads to a delocalized dipolar intervery mild valence isomerism conditions. l 2 mediate. Disrotatory collapse of this zwitterion to a Accordingly, we reasoned at the outset of this study that 1,3-dipolar ketone and sulfone intermediates were cyclopropanone probably then O C C U ~ S . ~ accessible from appropriate a-halo precursors. At the The 1,3 elimination of hydrogen halide from a-halo same time, the high reactivity of related zwitterion sulfones differs significantly in certain mechanistic detypes13 in intermolecular cycloaddition to homomultails. For example, although this reaction again inand heteromultiple bonds l 4 suggested that geovolves rapid and reversible carbanion f o r m a t i ~ n no , ~ ~ ~ tiple ~ metrically well-defined intramolecuhr variants of this comparable delocalized intermediate is involved. Large reaction could perhaps provide new dimension to the (1) U-Halo Sulfones. XXI. Part XX of this series: L. A. Paquette, R. E. Wingard, Jr., and R. H. Meisinger, J . Amer. Chem. Soc., 93, 1047
(1971). (2) We thank the National Cancer Institute and Eli Lilly and Co. for
funds used in partial support of this research. (3) National Institutes of Health Predoctoral Fellow, 1969-1971. (4) A. S. Kende, Org. React., 11, 261 (1960). (5) (a) L. A. Paquette, Accounts Chem. Res., 1, 209 (1968); (b) L. A. Paquette, “Mechanisms of Molecular Migrations,” Vol. I, B. S . Thyagarajan, Ed., Interscience, New York, N. Y . , 1968, pp 121-156; (c) F. G. Bordwell, Accourzts Chem. Res., 3, 281 (1970). (6) F. G. Bordwell, R. R. Frame, R. G. Scamehorn, J. G. Strong, and S . Meyerson, J . Amer. Chem. SOC.,89, 6704 (1967). (7) F. G. Bordwell and R. G. Scamehorn, ibid., 90, 6751 (1968). (8) F. G. Bordwell, R. G. Scamehorn, and W. R. Springer, ibid., 91, 2087 (1969).
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(9) F. G. Bordwell and J. W. Williams, Jr., ibid., 90, 435 (1968). (10) L. A. Paquette and R. W. Houser, ibid., 93,4522 (1971). (1 1) R. Desiderato and R. L. Sass, Acta Crystallogr., 23,430 (1967). (12) (a) W. L. Mock, Chem. Commun., 1254 (1970); (b) L. A . Paquette and S. Maiorana, ibid., 313 (1971).
(13) For leading references, see (a) J. W. Lown and ICHCl), 3.43 and 3.12 (center of AB doublets, J = 13.5 Hz, 2,-CH>SO?-),and 1.32and 1.16(s, 3each,methyl).
&L:13
Calcd for CloH13C10zS: C, 51.62; H , 5.63; Cl, 15.24. C, 51.33; H,5.61; C1,15.48. 7,8-Dimethyl-9.thiabicyclo[4.2.l]nona-2,4,7-triene9,g-Dioxide (34). T o a solution of 3.32 g (0.0144 mol) of an unpurified mixture of 32 and 33 in 100 ml of dry dimethyl sulfoxide was added in one portion 1.61 g (14 mmol) of potassium tert-butoxide. The temperature slowly rose from 25 to 35". After 10 min, the solution was cooled to 20" and 300 ml of ice-water was cautiously added and the mixture was extracted with ether (5 X 100 ml). Normal processing afforded 230mg(17%) of 34 as white crystals: mp 202" dec, from ~ ~ and l 1100cm-1; A ? 2 O H methylene chloride-ether; u ~ 1600,1290, 282 nm (e 2100); Sp$'g 5.83-6.08 (m, 4, olefinic), 3.62-3.95 (m, 2, bridgehead), and 1.88 (s, 6, methyl). Additional material, obtained by acidifying the aqueous layers and extraction with ether, brought the total quantity of isolated 34 to 509 mg (27%). Anal. Calcd for CIoHlsOzS: C, 61.19; H, 6.16; S, 16.34. Found: C, 61.21; H,6.41; S, 16.08. Photolysis of 34. A solution of 34 (68 mg) in 6 ml of acetone was irradiated with a 450-W Hanoria lamp through a Vycor filter for 4 hr. The solution was concentrated and preparative scale vpc purification was employed to obtain 5 mg (11 %) of 1,2-dimethylcyclooctatetraene (23), identical in all respects with the material obtained earlier. 9-Thiabicyclo[4.2.1]nona-2,4,7-triene 9,g-Dioxide (36). T o a stirred solution of 1.485 g (9.64 mmol) of 9-thiabicyclo[4.2.1]nona2,4,7-triene 9-oxideZ5jn 100 ml of methylene chloride was added dropwise during 1 hr at 0" 1.86 g (9.65 mmol) of m-chloroperbenzoic acid (89.5%) dissolved in 50 ml of the same solvent. The solution was stirred overnight at 25" and then washed with 25 ml portions of 0.5 M sodium hydroxide solution until alkaline and with water until neutral. Evaporation of the dried organic phase afforded 1.23 g (75%) of 36 as shiny white crystals: mp 193.5' dec, from methylene chloride-ether; ~2::~ 1390, 1125, and 1100 cm-1; 279 nm (e 2340); m/e calcd 168.0244, found 168.5.80-6.37 (m, 6, olefinic), and 3.78-4.15 (m, 2, bridge0242; 6$;G, 1' head). Anal. Calcd for C8H802S: C, 57.12; H, 4.79. Found: C, 56.90; H , 4.79. 1,2,3,4,5,10-Hexahydro-5,lO-epithiobenzocycl~ctene 11,ll-Dioxide (38a). T o a magnetically stirred solution of 109 mg (0.970 mmol) of potassium tert-butoxide in 50 ml of dry dimethyl sulfoxide under nitrogen was added 92.1 mg (0.356 mmol) of a-chloro sulfone 37a,23 and the intensely green solution was stirred for 20 min. With cooling, water (50 ml) was added and the solution was extracted with ether (3 X). The combined extracts were washed with water and saturated salt solution, dried, and evaporated to afford 43.8 mg of crude 38a as a yellow solid. Recrystallization from ether-hexane gave 32.1 mg (56.4%) of white crystals: mp 167.5-169.0' dec; Y::::"'1310, ' 1145, 1135, and ll00cm-I; 8%" 5.95 (m, 4, olefinic), 3.68 (br s, 2, >CHSOZ-), 2.13 (br s, 4, allyl), 282 nm (e 2100). and 1.74 (br s, 4, methylene); Anal. Calcd for C12Hl,02S: C, 64.85; H, 6.35; S, 14.10. Found: C,64.72; H,6.33; S, 14.33. 1,2,3,4,5,6,7,8,9,10-Decahydro-5,lO-epithiobenzocyclooctene 11,11Dioxide (40). A magnetically stirred solution of 38.7 mg (0.174 mmol) of 38a in 25 ml of ethyl acetate was hydrogenated at atmospheric pressure over ca. 100 mg of 10% palladium on charcoal. After the uptake of 2 equiv of hydrogen (15 min), the reaction mixture was filtered through a silica gel column and the solvent evaporated to yield 38.9 mg (99.5%) of 40 as white crystals: mp 138.0-139.0" from ether-hexane; "",:;Y 1290,1160, and lllOcm-I; 6;;:'' 3.55 (br s, 2, >CHSOz-) and 1.6-2.4 (envelope, 16, allyl and methylene). Anal. Calcd for C12H180rS: C, 63.70; H, 8.02; S , 14.14. Found: C,63.62; H,8.01; S, 14.15. Bicyclo[6.4.O]dodeca-1,7-diene (41). A 208 mg (0.923 mmol) sample of 40 was passed through a quartz chip packed quartz tube heated at 500" at 10 mm with a slow stream of nitrogen. There was obtained 110.2 mg (78.8%) of diene 41 as a pale yellow oil. Preparative vpc (5 ft X 0.25 in., 5 % Carbowax 20M on Chromosorb G, 130") gave an analytical sample of the hydrocarbon as a clear oil: uzi: 2910, 2850, 2800, 1445, 830, and 740 cm-l; B$::" 5.6 (br s, 2, olefinic), 2.0 (br s, 8, allyl), and 1.2-1.7 (envelope, 8, methylene); h~".ta"e228 nm ( E 5500) [lit. *? A ? 2 O K 221 (6640)l. Anal. Calcd for C12H18: C, 88.82; H, 11.18. Found: C , 88.60; H, 11.12. cis- and trans-Bicyclo[6.4.0]dodecanes. A. From Reduction of Bicyclo[6.4.0]dodeca-1,7-diene (41). A solution of 13.5 mg (0.084 mmol) of 41 in ethyl acetate was hydrogenated at atmospheric pressure over platinum oxide for 60 hr. Filtration and vpc analysis Anal.
Found:
Paquette, Meisinger, Wingard
1 Dehydrohalogenation
of a-Halo Ketones and Sulfones
2240 showed that two products had been formed in a 5:l ratio. The isomers were separated by preparative vpc (12 ft X 0.25 in., 10% Carbowax 6000 on Chromosorb G, 160"). The major isomer had the longest vpc retention time: :::v 2850, 2800, 2660, 1470, 1450, 1345, and 1000 cm-l; S$EI3 1.22 and 1.53 (centers of two broad overlapping singlets, high field signal has greater height). Anal. Calcd for C12H22: C, 86.66; H, 13.34. Found: C, 86.75; H , 13.34. The minor isomer had the shortest retention time: :::u 2850, 2800, 2660, 1480, 1460, 1445, and 1355 cm-'; 8:E;l3 1.19 and 1.59 (centers of two broad overlapping singlets, low field signal has greatest height). Anal. Calcd for CIzH22: C, 86.66; H , 13.34. Found: C, 86.74; H, 13.22. B. Reduction of Benzocyclooctene. A solution of 1.56 g (9.65 mmol) of benzocyclooctene in 100 ml of glacial acetic acid was hydrogenated for 72 hr over 250 mg of 5 % rhodium on alumina at 60" under 50 psi hydrogen in a Paar hydrogenation apparatus. The solution was diluted with water (600 ml) and extracted with pentane (3 X 250 ml). The extracts were washed with water, dried, and evaporated through a metal helix-packed column. Analysis of the clear residue by vpc showed two products were present in a 5 :1 ratio. The isomers were separated by preparative vpc (12 ft X 0.25 in., 10% Carbowax 6000 on Chromasorb G, 160") and were identical in every respect with those obtained above. Pyrolysis of 38a. A 120 mg (0.540 mmol) sample of 38a was passed through a quartz chip packed quartz tube heated at 400" at 10 mm with a slow stream of nitrogen. There was obtained 78.3 mg (91.5%) of tetraene 27 as a yellow oil. An analytical sample of the yellow liquid obtained by preparative vpc was identical in all respects with that isolated above. Photolysisof 38a. A solution of 10.7 mg (0.048 mmol) of 38a in 3 ml of acetone was irradiated with a 200-W Hanovia lamp equipped with Corex optics. Monitoring of the photolysis by tlc showed no sulfone remained after 30 min. Preparative vpc ( 5 ft X 0.25 in., 5 % Carbowax 20M on Chromosorb G, 130") was used to isolate the sole volatile component. It was spectrally identical with authentic 27. 2,3,4,5,6,11-Hexahydro-6,11-epithio-lH-cycloheptacyclooctene 12,12-Dioxide (38b). To a magnetically stirred solution of 666 mg (2.44 mmol) of oc-chloro sulfone 37bZ3in 75 ml of dry dimethyl sulfoxide under nitrogen was added 863 mg (7.70 mmol) of potassium tert-butoxide, and the dark green solution was stirred for 15 min. With cooling, 25 ml of ice-water was added and the solution
was extracted three times with ether. The combined extracts were washed, and dried, and the solvent was removed to afford 322 mg (5,.5i3%) of 38b: mp 149.5-150.5", from ether-methylene chloride; 5.90-6.10 (m, 4, olefinic), vmsx 1310, 1130, and 1110 cm-'; 8:2'3 3.73-3.97 (m, 2, >CHS02-), 2.22-2.58 (m, 4, allyl), and 1.35-1.95 (m, 6, methylene). Anal. Calcd for Ci3HI6O2S: C, 66.08; H, 6.83; S, 13.55. Found: C,66.06; H,6.94; S,13.32. Bicyclo[6.5.0]trideca-1,3,5,7-tetraene(39). A solution of 87.0 mg (0.368 mmol) of 38b in acetone was irradiated with a 450-W Hanovia lamp through a Corex filter for 60 min. By preparative vpc (6 ft X 0.25 in., 5 % SF-96 on Chromosorb G, 130") there was isolated 23.0 mg (37 %) of 39 as a yellow oil : uz:: 2960, 2890, 2820, 1450, and 690 cm-'; 285 sh nm (e 123); 8G : a'; 5.53-5.90 (m with sharp singlet at 5.75, 6, olefinic), 2.0-2.5 (m, 4, allyl), and I .57 (br s, 6, methylene). Anal. Calcd for C13Hi6: C, 90.64; H , 9.36. Found: C, 90.60; H, 9.52. 5,10-Dihydro-5,10-epithiobenzocyclooctene 11,ll-Dioxide (43). To a magnetically stirred solution of 234 mg (0.931 mmol) of a-chloro sulfone 4223 in 30 mi of dry dimethyl sulfoxide under nitrogen was added 112 mg (1.00 mmol) of potassium tert-butoxide, and the deep green solution was stirred for 30 min. With cooling, 50 ml of water was added and the solution was acidified with concentrated hydrochloric acid. The aqueous solution was extracted with chloroform and the extract was washed with water and brine and dried. Evaporation of the solvent and recrystallization from methanol-chloroform gave 137 mg (68.4%) of 43 as a white crystalline solid: mp 269.0-271.0" dec, from ether-chloroform; vI(m:i 1310, 1190, and 1100 cm-'; 8 ~ ~ ~7.43 ~ o (s, ~ 4, d aromatic), o 5.93 (br s, 4, olefinic), and 4.90-5.07 (m, 2, >CHSO,-); 267 sh (e 2280), 273 (2470). and 278 sh (228.0). Am/. Calcd for C12H1002S: C , 66.05; H, 4.62; S, 14.66. Found: C,65.77: H. 4.61; S, 14.82. Benzocyclooctatetraene (44) from 43. A solution of 25.0 mg (0.116 mmol) of 43 in acetone was irradiated for 3 hr with a 200-W Hanovia lamp equipped with a Vycor filter. Analysis of the photolysis solution showed only one volatile component. Preparative vpc (6 ft X 0.25 in., 5 % SF-96 on Chromosorb G, 120") gave 16.2 mg (91 %) of crystalline benzocyclooctatetraene (44), mp 4950", identical upon spectral comparison with an authentic sample. 48 (48) L. B. Anderson and L. A. Paquette, J . Amer. Chem. SOC.,94, 4915 (1972); L. Friedman and D. F. Lindow, ibid., 90,2329 (1968).
Olefin Isomerizations Accompanying the Hydroformylation of 3-Methyl- 1-hexene-3-d11 Charles P. Casey* and Clifford R. Cyr
Contribution f r o m the Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706. Received August 7, 1972 Abstract: The dicobalt octacarbonyl catalyzed hydroformylation of 3-methyl-1-hexene-3-dl (14) followed by methyl 3-(ethyl-l-dl)hexanoate ( 3 4 in addition t o the normal hydrooxidation and esterification gives 3.1 formylation products. The Eu(DPM)3-shifted nmr spectra of 3-d demonstrated that a 1,2 migration of deuterium h a d occurred in the hydroformylation of 1-d. This result taken together with Pino's observation that the hydroformylation of optically active 1 gives 3 with 70% retention of optical activity demonstrates that 3-d is formed by multiple isomerizations of the complexed alkene which immediately precede hydroformylation. The rate of isomerization of the complexed alkene consequently must be greater than the rate of decomplexation. A mechanism, previously proposed by Pino, involving direct insertion of cobalt into a carbon-hydrogen bond of a methyl group, is directly refuted by the results obtained here.
ydridotetracarbonylcobalt is the active catalyst in the dicobalt octacarbonyl catalyzed hydroformylation Of olefins.2 Depending on the reaction conditions (1) Some of the results described in this paper have appeared in Preliminary form: C. P. Casey and C. R. Cyr, ,J. Amer. Chem. Soc., 93, 1280 (1971).
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employed, olefin isomerization accompanying hydro(2) For reviews of hydroformylation, see (a) A. J . Chalk and J . F. Harrod, Adcnn. Organomeral. Chem., 6 , 119 (1968); (b) R. F. Heck, ibid., 4, 243 (1966); (c) C. W. Bird, "Transition Metal Intermediates in Organic Synthesis," Academic Press, New York, N. Y.,1967, Chapter 6.
