Nagendrappa, Gopalpur

Prasad, S Hari

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Indian Journal ChemistryVoL 368, August 19')7, pp. 6')1 - (,94Vinylsilanes in synthesis: 2-Halo-l-cyclopentenyl alkyl/aryl ketonesfrom 2-halo-l-trimethylsilylcyclo-pentenesSHari Prasad & Gopalpur Nagendrappa*Department of Chemistry, Bangalore University(Central College campus), Bangalore 560 001, IndiaReceived 31 October 1996; revised and accepted 2 April 19972-8romo - and 2 - chloro - I - trimethylsily\cyc\opent-l-cne undergo Friedel-Crans reaction in smoothly with avariety of acyl halides in the presence of aluminiumchloride at - 15°C, through the displacement of thetrimethylsilyl group by acyl group to produce thecorresponding 2-halocyclopentenyl alkyl/aryl ketones6a-o, many of which are reported for the first time,The yields vary from 62-92%. The reaction is very fa-cile and is believed to owe its success to the well esta-blished ~-silicon effect.Halocyclopentenyl ketones 6 have found applic-ations in the synthesis of steroid related com-pounds I, anti-hypertensive pharmaceuticals- andheterocycles='. They have also been used in me-chanistic studies), There are very few proceduresfor the preparation of only a limited number ofthem starting from cyclopentanone, with moderateyields?". Cyclic vinylsilanes have been very suc-cessfully used for the synthesis of cycloalkenyl al-kyl/aryl ketones by Friedel-Crafts reaction using anumber of acyl halides":". We had synthesised2-halo-l-trimethylsilylcyclopentenes 5a and 5b ingood yields 13. These appeared to be promisingstarting compounds for the preparation of halo-cyclopentenyl ketones 6 through the Friedel-Crafts acylation .procedure. We have achievedconsiderable success in this attempt and the re-sults are reported here.Ct" PCts/Et20 crl XY o.y." • a. lSOC /I CIICI3/00c II....x2Note(ySiMC3Ll(. +ySaSboAICI3 •• ~Ry6a-g: Y=Br6h-n: Y=CIRCOCIWurtz-Fittig procedure was employed for thesynthesis of a variety of I-trimethylsilylcycloal-kenes starting from the corresponding l-chloro-or l-bromocycloalkenes t ~,15, When the same wasextended. using excess reagents (sodium andchlorotrimethylsilane), to 1, 2-dihalocyclopentenesa novel hemocyclic ring opening was observed,which was investigated thoroughly":". However,by careful manipulaton of the experimental condi-tions, success was achieved in preparing 2-chloro-and 2-bromo-l-trimethylsilylcyclopentene(Scheme I). Though l-trimethylsilylcycloalkenesundergo Friedel-Crafts reactions smoothly, it wasnot known how a halogen on the adjacent vinylicposition like in 5 would affect this reaction. It issatisfying to find that in these cases also the acyla-tion, using a number of different acyl halides inpresence of aluminium chloride, is smooth and itis now possible to make halocycloalkenyl ketoneslike 6 by a simple and efficient procedure(Scheme II). The ease of this reaction is attribut-able, as in other such reactions, to the ~-siliconeffect!"!", and the mechanism may follow a simi-lar path. It is fortunate that the vinylic halogen in5 is not attacked by the Lewis acid (AlCl,~), prob-ably because of the very mild reactioa condition.The yields, boiling points and elemental ana-lyses are provided in the Table I. The UV spectraof the alkyl ketones (6a-f and 6h-m) exhibitedAmox at 253 nm and the phenyl ketone (6g and6n) showed two Am ax at 253 and 214 nm. The 'Hatc.KOlt •J 4 sX=Y=Br Ja: X=Y=BrX=Br; Y=CI Jb: X=Br: Y=CIX",Y=O Jc: X=Y=CI4a: X=Y=Br4b: X=Br; Y=CI4c: X=Y=CISa: Y=BrSb: v-oScheme I692 INDIAN J. CHEM. SEC B, AUGUST 1997Table I-Yields and analytical data of halocyclopentenyl alkyl/aryl ketonesStarting compd Acyl halide Products Yield B.P. Mol. Found % (Calc.)2-bromo-l-trimethyl- (RCOCI) 2-bromocyclopentenyl (Ofu) °C/Torr formula C Hsilylcyclopentene (Sa) alkyl/aryl ketonesR=Me R=Me(6a) 65 80/4.5 C7H'IBrO 44.52 4.n(44.47 4.80)Et Et(6b) 73 65/1.5 CxHllDrO 47.27 5.31(47.31 5.46)n-Pr n-Pr(6c) 80 65-68/1.0 C.HuBrO 41).83 5.1)4(41).71) 6.03)i-Pr i-Pq6d) 75 75-7612.0 C"H,.,BrO 41).1)4 6.12(41).79 6.03)n-Bu n-Bu(6e) 85 80-8312.0 CIUH,~BrO 52.08 6.58(51.96 6.54)n-Am n-Am (6f) 1)2 115-120/3.0 C"H17BrO 53.1)6 7.08(53.1l9 6.99)Ph Ph (6g) 78 125-128/2.5 C"H"BrO 57.52 4.57(57.39 4.42)2-chloro-l-trimethyl- 2-chlorocyclopentenylsilylcyclo pentene( Sb ) alkyl/aryl ketonesR=Me R=Me(6h) 68 72-75/5.0(91-92122)*Et Et(61) 73 85-88/9.0(97-9R/13)*n-Pr n-Pr(6j) 80 68- 70/ 4.0(106-107/X)*i-Pr i-Pr(6k) 63 65-70/4.0 C"H"ClO 62.73 7.67(62.61 7.59)n-Bu n-Bu(61) 75 80-82!2.5 CIUHI~CIO 64.18 7.98(64.34 1l.IO)n-Am n-Am (6m) I}O 120-125/6.0 C"H17C10 66.()J 8.59(6~.X2 X.54)Ph Ph(6n) 62 115-120/1.5 C,"H"ClO 61).96 5.41(69.74 5.37)* Literature b.p. reponed in ref. 6.NMR and mass spectral data are given in the ex-perimental section ..Attempts were made to carry out Friedel-Craftsalkylation on 5a and 5b using several alkyl ha-lides, which usually led to unidentifiable polymer-ic material. Variations in experimental conditionsand Lewis acid catalyst also did not give any use-ful results. Thus whereas the acylation of 5a and5b is an immensely fruitful reaction, the alkylationis not of any practical use. It should be noted thateven acylation would be useless in the absence ofsilyl substituent.Pr'''Experimental Section'H NMR spectra were recorded on JEOL FX-90Q and Bruker AC-250 spectrometers usingCDCl3 as solvent and TMS as internal standard(chemical shifts in b, ppm), IR spectra on Carl-Zeiss 75 and Nicolet 5DXC FT-IR spectropho-tometers, with films of liquid samples betweenNaCl plates and UV spectra on Shimadzu UV-160 spectrophotometer. GC-MS were obtainedon Hewlett-Packard 5985B system attached to aHewlett-Packard 5B40A gas chromatograph. GCanalyses were carried out on a Varian Vista 6000gas chromatograph using 5% OV-101 , 10% OV-101 and 15% FFAP columns with different tem-perature programmes.The acid chlorides, propionyl chloride, iso-butyryl chloride, n-valeryl chloride and n-caproylchloride, were prepared according to standardprocedures by reacting the organic acid withabout 25% excess of thionyl chloride". Acetylchloride and benzoyl chloride were commercialsamples. All the acid chlorides were distilledtwice before use. Dichloromethane was distilledover phosphorus pentoxide. Commercial alumini-um chloride was used without further purification.General procedure for the Friedel-Crafts reac-tion. All the reactions were carried out using ap-proximately 0.5 g or 1.0 g of the vinylsilane 5a!5b. Each reaction was repeated 3 to 4 times andthe yields were optimised.To a mange tically stirred mixture of 3 molarequivalents of anhydrous AICl3 and 3 molarequivalents of acid chloride in dry CH~C1~ (50ml.), cooled to - 15°C on an ice-salt bath, wasadded the vinylsilane 5a/5b (0.5 g or 1.0 g) in 25ml of dry CH2CI2 dropwise over a period of 1hr. Saturated NaHCO, solution (25 mL) was thencarefully added to the reaction mixture andstirred for 30 min, smultaneously allowing thereaction mixture to attain room temperature. Theorganic layer was separated and washed with sat-urated NaHCOj solution (2 x 25 rnl.), water (25ml.) and saturated NaCl solution (25 ml.), Afterdrying over Na2S04, the solvent was stripped andthe residue was purified by bulb to bulb distilla-tion under reduced pressure.2-Bromo-l-ethanoylcyclopent-l-ene 6a. IR:28'70, 2860, 1660, 1600, 1435, 1'360, 1265 and1040 em-I; IH NMR: 1.81 (m, 2H), 2.40 (s, 3H)and 2.75 (rn, 4H); MS (relative intensity): mlz 190(40.5), 188 (40.8) (M+), 175 (100), 173 (93.9),147 (3.6), 145 (4.4) (M+ -Ac), 134 (3.3), 119(11.9), 109 (12.0) (M + - Br), 94 (20.9), 79 (2.8),66(22.7),65 (37.3), 51 (4.4) and 43 (32.5).2-Bromo-l-propanoylcyclopent-l-ene 6b. IR:2870, 1640, 1580, 1425. 1345, 820 and 715em -I; IH NMR: 1.08 (t, J= 7.2 Hz, 3H), 2.0 (q,J= 7.2 Hz, 2H), 2.73 (m, 2H) and 2.92 (t, J= 7.2Hz, 4H); MS (relative intensity): mlz 204 (I8.9),202 (19.1) (M+), 175 (98.1),173 (100),147 (3.0),145 (3.1), 119 (3.3), 117 (2.6), 107 (0.5), 94 (13.4),77 (1.3), 66 (12.3), 65 (19.4), 51 (1.8), 39 (8.6)and 27 (4.5).2-Bromo-l-butanoylcyclopent- t -ene 6c. IR:2960, 1660, 1595, 1460, 1410, 1360 and 795em-I; IH NMR: 0.93 (t, J= 7.2 Hz, 3H), 1.65 (q,J= 7.2 Hz, 2H), 1.97 (rn, J= 7.2 Hz, 2H), 2.75(m, 4H) and 2.8 (t, J= 7.7 Hz, 2H);MS (relativeintensity): mlz 218 (3.0), 216 (4.0) (M+), 190 (8),188 (7), 173 (96), 171 (100), 147 (5.0), 145 (4.5),137 (34.0) (M+ - Br), 129 (8.0), 94 (28), 77 (8),71 (17.5), 66 (52.5), 65 (88.0).2-Bromo- t - (2' -methylpropanoyl)cyclopent- t-ene 6d. lR: 2860, 1660, 1590, 1420, 1340, 1060and 865 em-I; IH NMR: 1.19 (d, J= 7.6 Hz, 6H),2.0 (q, J= 7.6 Hz, 2H), 2.74 (m, 4H) and 2.42(septet, J= 7.6 Hz, 1H); MS (relative intensity):mlz 218 (10.3), 216 (10.9) (M+), 203 (0.1), 190(0.3), 175 (97), 173 (l00) (M+ - C3H78)' 147 (2.5),107 (0.6), 94 (11.5), 77 (1.1), 66 (13.1) and 65(20.7).2-Bromo- t -pentanoylcyclepent- t -ene 6e. IR:2980, 1720, 1680, 1340, 1100, 920 and 860em-I; IH NMR: 0.86 «, J=4 Hz, 3H), 1.38 (m,6H), 1.93 (m, 2H) and 2.63 (m, 4H); MS (relativeintensity): mlz 232 (0.2), 230, (0.2) (M+), 203NOTES(1.4),190 (45.9), 188 (46.4) (M+ -C3H7 throughMclafferty rearrangement), 175 (100.0), 173(95.7), 151 [M+ - Br}, 119 (2.2), 109 (1.0), 94(15.0),77 (1.6),66 (18.5) and 65 (26.4). .2-Bromo- t -hexanoylcyclopent- t -ene 6f. IR:2870, 1650, 1580, 1350, 1160, 1050, 830, 800720 em-I; IH NMR: 0.95 (t, J=7.2 Hz, 3H),1.36 (m, 4H), 1.84 (t, J=6.12 Hz, 2H), 1.98 (q,J= 7.2 Hz, 2H), 2.40 (m, 2H), 2.78 (m, 2H) and2.82 (r, J= 7.2 Hz, 2H); MS (relative intensity):m/z 244 (0.2), 242 (0.2) (M+), 218 (0.2), 203(2.1), 201 (2.0) (M+ -C1H7), 190 (57.0), 188(59.0) (M + - C4H\I through Mclafferty rearrange-ment), 175 (95.9), 173 (100), 165 (M+ - Br), 147(2.7), 131 (0.1), 109 (3.1), 94 (l1.3), 79 (3.1), 66(13.7) and 65 (20.8).I-Benzoyl- 2-bromocyclopent-I-ene 6g. IR:3080, 3040, 2920, 2100-1900 (weak benzenoidbands), 1600 (broad), 1460, 1360 and 830 em - I;IH NMR: 2.16 (m, 2H), 2.81 (m, 4H) and ca 7.3(complex, 5H); MS (relative intensity): mlz 252(48.5), 250 (48.8) (M+), 171 (100) (M+ - Br), 153(9.9), 143 (50.5), 128 (37.4), 115 (16.3), 105(84.1),94 (9.7), 77 (75.9), 66 (19.6), 65 (32.7), 51(27.9) and 39 (15.0).2-Chloro-l-ethanoylcyclopent-l-ene 6h. IHNMR: 1.95 (quintet, J= 7.2 Hz, 2H), 2.48 (s, 3H)and 2.70 (m, 4H); MS (relative intensity): mlz 146(12.9),144 (39.9) (M+), 131 (32.1),129 (100)(M+ -CH,), 109 (3.9) (M+ -Cl). 103 (2.1), 101(6.9), 93 (1.2), 81 (1.7), 73 (3.5), 66 (12.0), 65(43.1), 51 (1.9),43 (18.2),39 (11.6), 27 (1.4) and15 {1.9). .2-Chloro-I-propanoylcyclopent-l-ene 6i. IR:2975, 2940, 1665, 1607, 1459, 1436, 1410,1377,1364,1238,1195,1074 and 966 em-I; IHNMR: i.o: (t, J= 7.7 Hz, 3H), 1.92 (quintet,J= 7.7 Hz, 2H), 2.55 (t, J= 7.7 Hz, 2H) and 2.75(m, 4H); MS (relative intensity): m/z 160 (3.9),158 (12.9) (M+). 131 (31.5), 129 (97.3)(M+ - C2H5), 103 (4.9), 101 {17.5}, 75 (5.7), 73(11.2), 66 (l6.6), 65 (100), 39 (59.3), 29 (36.7)and 27 (33.8).I-Butanoyl- 2-chlorocyclopent-l-ene 6j. IR:2964, 2936, 2904, 2875, 1664, 1605, 1465,1457, 1436, 1404, 1378, 1193, 1181 and 1085em - I; :H NMR: 0.82 (t, J= 7.7 Hz, 3H), 1.67 (tlq, J= 7.7 Hz, 2H), 1.82 (quintet, J= 7.7 Hz, 2H),2.60 (complex m, 4H), and 2.69 (t, J= 7.7 Hz,2H); MS (relative intensity): mlz 174 (0.4), 72(1.1) (M+), 159 (0.4), 157 (1.1) (M+ -CH,), 146(3.6), 144 (1O.5) (M+ - C2H,), 131 (33.8), 129(100) (M+ -C,H7), 103 (1.7),101 (4.5),77 (7.5),65 (7.5), 51 (0.5),39 (2.4), 27 (0.8) and 15 (0.1).694 INDIAN J. CHEM. SEC B. AUGUST 19972-Chloro-l- (2' -methylpropanoyl)cyclopent- ~-ene 6k. IR: 2973, 2936,2891, 2876, 1736, 1731,1712, 1664, 1600, 1467, 1384, 1239, 1196, 1167and 1087 cm-I; IH NMR: 1.15 (d, J= 7.7 Hz,6H), 1.00 (s, 3H), 1.87 (quintet, J= 7.7 Hz, 2H),2.62 (complex m, 4H) and 3.31 (septet, IH); MS(relative intensity): m/z 174 (2.8), 172 (&.6) (M t),157 (0.1) (M+ -CHJ), 144 (M+ -C~H:'). 131(31.6), 129 (100) (M+-CJH7)' 103 (1.0), 101(3.2),75 (1.0) and 65 (10.2).2-Chloro-l-pentanoylcyclopent-l-ene 61. lR:2960,2935,2874,1734,1711,1690,1685,1664,1605, 1466, 1457, 1436, 1405, 1380, 1259. 1189.1180 and 1036 cm -I; IH NMR: 0.92 (t, J= 7.7Hz, 3H), 1.31 (m, 2H), 1.58 (m, 2H), 1.87 (quin-tet, 2H), 2.66 (complex m, 4H) and 2.80 (t, 2H);MS (relative intensity): mJz (M+ peak absent),159 (0.7), 157 (1.9) (M+ -C2H~), 146 (15.2), 144(44.6) (M + - CJH7 through McLafferty rearrange-ment), 131 (30.9), 129 (100) (M+ -C4H'I)' 103(1.6),101 (4.1),77(1.3),65 (16.0)and 39(4.8).2-Chloro-l-hexanoylcyclopent-l-ene 6m. IR:2958, 2933, 2873, 2861, 1711, 1665, 1606,1467,1460,1435,1412,1379,1297,1248,1212,1180, 1087 and 795 cm-I; 'H NMR: 0.88 (t,J= 7.7 Hz, 3H), 1.29 (m, 4H), 1.52 (m, 2H), 1.90(quintet, J= 7.7 Hz, 2H), 2.62 (m, 4H) and 2.74(t, J= 7.7 Hz, 2H); MS (relative intensity): mlz200 (0.2) M+, 187 (0.2) (M+ -CH~), 172 (0.2),165 (6.7) (M+ -CI), 157 (1.9), 146 (14.7), 144(44.3) (M + - C4H<j through McLafferty rearrange-ment), 131 (28.6), 129 (100) (M + - C5H 11)' 109(3.9), 103 (4.8), 101 (14.6), 91 (5.3), 77 (6.9), 66(15.1), 65 (89.0), 55 (10.5), 39 (46.3) and 29(19.7).I-Benzoyl-z-chlorocyclopent-j-ene 6n. IR: 2956,2954, 2952, 2939, 2718, 1700, 1685, 1663,1653, 1646, 1597, 1449, 1315, 1277, 1258, 1249,1214, toOl, 836 and 712 cm-I; IH NMR: 2.02(m, 2H), 2.60 (rn, 4H), 7.47 (m, 3H) and 8.02 (m,2H); MS (relative intensity): mJz 208 (21.3), 206(53.4) (M+), 171 (39.7) (M+ -CI), 115 (11.5),105(100), 89 (5.7), 77 (100) (C(,Hs), 65 (42.5), 51(28.7),39 (10.3), 27 (6.6) and 18 (10.1)..'AcknowledgementThe authors are thankful to the DST, New Del-hi, for financial assistance. S.H. thanks UGC, NewDelhi, for a fellowship. We are grateful to Prof. K.Griesbaum, Karlsruhe University, Karlsruhe, andAlexander von Humboldt-Foundation, Germany,and Chairman, Department of Organic Chemistry,l.I.Sc., Bangalore, for providing spectra and otheranalytical facilities.ReferencesI Brown E. Touet J & Regault M. Bull Soc Chim France.1972.212.2 Engel J,Kleeman A, Possell K, Stroman F & Thiemer K,Ger Patent. 2.919.495. 1979. Chern Abstr. 92. 1980,lI06H2 f.3 Spitzner R, Mielke D, Scholz D, Schroth W & Preiss A,Tetrahedron, 38,1982,927.4 Schroth W. Spitzner R. Koch B. Freitag S & Mielke D.Tetrahedron. 38,1981, '137.5 Beltrarne P, Favini G, Cattania M G & Guella F, GaggChim Ital, 98, 1968, 380.{, Kochetkov N K. Nifantaev E E & Shibaev V N. ZhurObschei Chim. 2'1. 1959, 2324; Chern Abstr. 51. 1959,9786d.7 Kochetkov N K, Nifantaev E E & Shibaev V N, DoklAkad Nauk USSR. 117. 1957, 241; Chern Abstr, 52.1958, 5'JH5 c.H Panek J S, SlwII stablzuton ill comprehensive organicchemstry, Vol I, Part I, edited by B M Trost (Pergamonpress. New York). 1991.'I Birkofer L & Stuhl D. The chemistry of organc sliconcompounds, edited by S Patai & Z Rappoport (Wiley,New York), 1989.10 Blumenkopf T A & Overman L E. Chern Rev. 86. 1986.H57.II Fleming I, Dounogues J & Smithers R, Org React, 1989,57.12 Bandodakar B S & Nagendrappa G. Tetrahedron Left. 30.1989,7461.13 Hari Prasad S & Nagendrappa G. Tetrahedron. 49. 1993,3387.14 Nagendrappa G. Synthess. 1980,704.15 Hudrlik P F, Kulkarni A K. Jain S & Hudrlik A M. Te-trahedron, 39,1983,877.16 Nagendrappa G, Tetrahedron Lett, 30,1989,121.17 Wierschke G S. Chandrasekhar J & Jorgensen W L. J AmChern Soc. 107,1985,1496.18 Lambert J B, Tetrahedron, 46,1990, 2677.19 GrovesJK, Chern Soc Rev, 1,1972, 73.20 Tubul A & Santelli M. Tetrahedron. 44,1988,3975.21 Vogel A I, Practical organic chemistry, IV Edn (ELBS &Longman, London), 1978 .

Vinylsilanes in synthesis: 2-Halo-lcyclopentenyl alkyl/aryl ketones from 2-halo-1-trimethylsilylcyclopentenes

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Vinylsilanes in synthesis: 2-Halo-lcyclopentenyl alkyl/aryl ketones from 2-halo-1-trimethylsilylcyclopentenes

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