Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) -Ferrocenylvinylacetylenes Elena I. Klimova,*a Marcos Martinez Garcia,b Tatiana Klimova,a Lena Ruiz Ramireza and Jose Manuel Mendez Stivaleta a Department of Chemistry, National Autonomous University of Mexico, CP 04510 Mexico DF, Mexico. Fax: +5 25 622 5366; e-mail: klimova@servidor.unam.mx b Institute of Chemistry, National Autonomous University of Mexico, CP 04510 Mexico DF, Mexico.Fax: +525 616 2203 Thermolysis of 3-isopropyl- and 3-cyclobutyl-3-ferrocenylcyclopropenes results in the formation of 3-alkylidene-3-ferrocenylpropynes and (Z,E)-1-alkyl-1-ferrocenylpropenes; 2,2-dibromo-1-methyl-, 2,2-dibromo-1-isopropyl- and 2,2-dibromo-1-cyclobutylferrocenylcyclopropanes are converted into ferrocenylvinylacetylenes on treatment with ButOK in THF.It is well known that the introduction of a ferrocenyl substituent into a cyclopropane or cyclopropene ring substantially alters its properties. The transformations of gem-dihalo(ferrocenyl)cyclopropanes into 1,2- and 1,3-dienes under the action of BuLi or Na2CO3 in ethanol1–3 and of 2,2-dibromo-1-alkyl-1-ferrocenylcyclopropanes into monobromides, cyclopropenes and retrocyclization products upon treatment with ButOK in DMSO are the examples.4 3-Aryl-3-ferrocenylcyclopropanes easily undergo intramolecular transformations with small-ring opening followed by retrocyclization involving the aryl fragment.5–8 The reaction of 3-ferrocenyl-3-methylcyclopropene 1a with 1,3-diphenylisobenzofuran (DPIBF) also proceeds in an unusual way, the main product being compound 2, viz., an adduct of DPIBF with 3-ferrocenylbut-3-ene-1-yne 3a formed upon small-ring opening under reaction conditions, as depicted in the scheme.9 All attempts to identify 3-ferrocenylbut-3-ene-1-yne 3a under conditions of cyclopropene 1a thermolysis (refluxing in dry benzene, toluene or xylene in an inert atmosphere), without DPIBF or any other trap for expected 3a were unsuccessful.The only product isolated from the reaction mixture was 2-ferrocenylbut- 2-ene 5a, supposedly, as the trans-isomer. In addition, some other polymeric products of unknown structures were isolated. There are only two reports available in the literature concerning the synthesis of a-ferrocenyl-substituted vinylacetylenes, namely, 3-ferrocenyl-3-cyclohexylidenepropyne.1,3 This compound was synthesised by prolonged refluxing of 1,1-dibromo- 2-cyclohexyl-2-ferrocenylcyclopropane in ethanol (18% yield) or acetonitrile (48% yield) in the presence of Na2CO3.The absence of other data on the chemical properties of ferrocenylenynes and on convenient methods of their synthesis indicates that this class of compounds has not been adequately studied. On the other hand, these compounds can be used for the synthesis of ferrocene derivatives and for studies of the influence of a bulky ferrocenyl substituent on the reactions of conjugated enynes.We examined the preparation of this compounds by thermolysis of 3-alkyl-3-ferrocenylcyclopropenes with secondary alkyl substituents [alkyl = isopropyl (1b) or cyclobutyl (1c)].† We found that these compounds, in contrast to 3-ferrocenyl-3-methylcyclopropene 1a, afford 3-alkylidene-3-ferrocenylpropynes (3b,c)‡ and (Z,E)-1-alkyl-1-ferrocenylprop-1-enes (5b,c)§ as the main products on refluxing in benzene, together with small amounts of methyl vinyl ketones (6b,c),¶,†† respectively.The structures of the compounds obtained were established on the basis of the 1H and 13C NMR spectra and elemental analysis data.Thermolysis of cyclopropenes 1b,c in the presence of DPIBF†† leads to the formation of Diels–Alder adducts 7b,c and compounds 3b,c, 4, 5b,c and 6b,c. The Diels–Alder adducts were obtained as mixtures of two structural isomers 7b1 and 7b2 or 7c1 and 7c2 (~3:1),‡‡ as was found by 1H NMR spectroscopy.The X-ray analysis of the major isomers formed indicates that their structures correspond to exo-1,5-diphenyl-3-anti-ferrocenyl- 3-syn-isopropyl(or cyclobutyl)-6,7-benzo-8-oxatricyclo[3.2.1.02,4]- oct-6-enes (7b1,c1). The structures of minor isomers have not been established as yet. It is quite obvious that in this case heterolysis of a C–C bond of the cyclopropane ring leads to carbenoids 8b,c.We believe † gem-Dibromocyclopropanes 9b,c and cyclopropenes 1b,c were synthesised according to the published procedures.4,7–9 1b: yield 61%, orange crystals, mp 62–63 °C. 1H NMR (hereinafter, CDCl3) d: 0.79 (d, 6H, Me, J 6.73 Hz), 2.41 (m, 1H, CH, J 6.73 Hz), 4.12 (s, 5H, C5H5), 4.02 (s, 4H, C5H4), 6.95 (s, 2H, CH=). 13C NMR (hereinafter, CDCl3) d: 20.70 (Me), 29.91 (CH), 34.90 (C), 66.95 (C5H4), 68.01 (C5H5), 98.73 (CipsoFc), 110.59 (CH=).Found (%): C, 72.29; H, 7.03; Fe, 21.08. Calc. for C16H18Fe (%): C, 72.21; H, 6.81; Fe, 20.98. 1c: yield 52%, orange crystals, mp 66°C. 1H NMR, d: 1.60–2.25 (m, 6H, CH2), 2.85 (m, 1H, CH), 4.11 (s, 5H, C5H5), 3.97 (m, 2H, C5H4), 4.02 (m, 2H, C5H4), 7.05 (d, 2H, CH=, J 0.8 Hz). 13C NMR, d: 14.67, 16.97 (CH2), 29.99 (CH), 33.98 (C), 66.91 (C5H4), 68.00 (C5H5), 98.65 (CipsoFc), 109.93 (CH=).Found (%): C, 73.56; H, 6.38; Fe, 20.14. Calc. for C17H18Fe (%): C, 73.40; H, 6.52; Fe, 20.08. ‡ 3a: yield 52%, orange oil. 1H NMR, d: 3.01 (s, 1H, CH=), 4.16 (s, 5H, C5H5), 4.24 (m, 2H, C5H4), 4.51 (m, 2H, C5H4), 5.47 (d, 1H, CH2, J 0.9 Hz), 5.60 (d, 1H, CH2, J 0.9 Hz). 13C NMR, d: 66.67, 69.09 (C5H4), 69.65 (C5H5), 76.51 (CH=), 82.93 (CipsoFc), 89.97 (C=), 118.15 (CH2=), 128.42 (C).Found (%): C, 71.33; H, 4.99; Fe, 23.54. Calc. for C14H12Fe (%): C, 71.22; H, 5.12; Fe, 23.66. 3b: yield 61%, orange oil. 1H NMR, d: 1.85 (s, 3H, Me), 2.02 (s, 3H, Me), 2.89 (s, 1H, CHº), 4.12 (s, 5H, C5H5), 4.15 (m, 2H, C5H4), 4.19 (m, 2H, C5H4). Found (%): C, 72.87; H, 6.03; Fe, 21.19.Calc. for C16H16Fe (%): C, 72.75; H, 6.11; Fe, 21.14. 3c: yield 53%, orange oil. 1H NMR, d: 1.81–2.53 (m, 6H, CH2), 3.01 (s, 1H, CHº), 4.14 (s, 5H, C5H5), 4.18 (m, 2H, C5H4), 4.29 (m, 2H, C5H4). Found (%): C, 73.85; H, 6.05; Fe, 20.07. Calc. for C17H16Fe (%): C, 73.93; H, 5.84; Fe, 20.23. a Me Fc Fc H H H H H 1a C C CH H2C Fc DPIBF 3a O Ph Ph 4 DPIBF Ph Ph O C Fc CH 2 Fc = C5H5FeC5H4 C C Me Fc H Me 1a D + polymers 5aMendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) that compounds 3b,c and 5b,c result from disproportionation of carbenoids 8b,c according to the following scheme: Methyl vinyl ketones 6b,c are formed upon hydration of acetylenes 3b,c during chromatographic separation of the reaction mixtures. The fact that 1,3-dihydro-1,3-diphenylisobenzofuran 4 is formed during the thermolysis of cyclopropenes 1a9 and 1b,c in the presence of DPIBF indicates that 1,3-diphenylisobenzofuran can act as a partner in the disproportionation of carbenoids 8a–c § 5a: yield 28%, orange oil. 1H NMR, d: 1.44 (d, 3H, Me, J 6.67 Hz), 1.78 (s, 3H, Me), 4.06 (s, 5H, C5H5), 4.01 (m, 2H, C5H4), 4.23 (m, 2H, C5H4), 5.52 (q, 1H, CH=, J 6.67 Hz).Found (%): C, 69.87; H, 6.93; Fe, 23.41. Calc. for C14H16Fe (%): C, 70.02; H, 6.72; Fe, 23.26. (Z,E)-5b (2:1), Rf = 0.75 (hexane), yield 30.5%, orange oil. 1H NMR for (Z)-5b, d: 1.17 (d, 6H, Me, J 6.8 Hz), 1.81 (d, 3H, Me, J 6.6 Hz), 2.40 (m, 1H, CH, J 6.8 Hz), 4.05 (s, 5H, C5H5), 4.00 (m, 1H, C5H4), 4.20 (m, 2H, C5H4), 4.27 (m, 1H, C5H4), 5.51 (q, 1H, CH=, J 6.6 Hz); for (E)-5b, d: 1.19 (d, 6H, Me, J 6.75 Hz), 1.70 (d, 3H, Me, J 6.62 Hz), 2.75 (m, 1H, CH, J 6.75 Hz), 4.03 (s, 5H, C5H5), 3.75 (m, 1H, C5H4), 4.02 (m, 1H, C5H4), 4.18 (m, 1H, C5H4), 4.43 (m, 1H, C5H4), 5.83 (q, 1H, CH=, J 6.62 Hz).Found for (Z,E)-5b (%): C, 71.52; H, 7.65; Fe, 20.98. Calc. for C16H20Fe (%): C, 71.66; H, 7.51; Fe, 20.83. (Z,E)-5c (2.5:1), Rf = 0.71 (hexane), yield 28.1%, orange oil. 1H NMR for (Z)-5c, d: 1.48 (d, 3H, Me, J 6.8 Hz), 1.63–2.40 (m, 6H, CH2), 2.85 (m, 1H, CH), 4.12 (s, 5H, C5H5), 4.02 (m, 2H, C5H4), 4.16 (m, 2H, C5H4), 5.84 (q, 1H, CH=, J 6.8 Hz); for (E)-5c, d: 1.76 (d, 3H, Me, J 7.3 Hz), 1.82–2.40 (m, 6H, CH2), 2.55 (m, 1H, CH), 4.15 (s, 5H, C5H5), 3.86 (m, 2H, C5H4), 4.07 (m, 2H, C5H4), 5.50 (q, 1H, CH=, J 7.3 Hz). Found for (Z,E)-5c, (%): C, 72.74; H, 7.27; Fe, 20.06. Calc.for C17H20Fe (%): C, 72.87; H, 7.19; Fe, 19.94. ¶ 6a: yield 8%, violet crystals, mp 67–68 °C. 1H NMR, d: 1.98 (s, 3H, Me), 4.18 (s, 5H, C5H5), 4.25 (m, 2H, C5H4), 4.47 (m, 2H, C5H4), 5.71 (s, 1H, CH2), 5.89 (s, 1H, CH2). Found (%): C, 66.24; H, 5.32; Fe, 22.04. Calc. for C14H14FeO (%): C, 66.17; H, 5.55; Fe, 21.98. 6b: yield 15%, violet crystals, mp 71–72 °C. 1H NMR, d: 1.74 (s, 3H, Me), 1.96 (s, 3H, Me), 2.05 (s, 3H, Me), 4.23 (s, 5H, C5H5), 4.32 (m, 2H, C5H4), 4.54 (m, 2H, C5H4). Found (%): C, 68.29; H, 6.27; Fe, 19.93. Calc. for C16H18FeO (%): C, 68.11; H, 6.43; Fe, 19.7. 6c: yield 12%, violet crystals, mp 74–75 °C. 1H NMR, d: 1.93 (s, 3H, Me), 1.98–2.68 (m, 6H, CH2), 4.21 (s, 5H, C5H5), 4.31 (m, 2H, C5H4), 4.46 (m, 2H, C5H4).Found (%): C, 69.66; H, 6.04; Fe, 18.78. Calc. for C17H18FeO (%): C, 69.41; H, 6.20; Fe, 19.00. †† Synthesis of 3-alkylidene-3-ferrocenylpropynes 3a–c. gem-Dibromoferrocenylcyclopropanes 9a–c (2 mmol) were added to a solution of ButOK (0.56 g, 5 mmol) in dry THF (50 ml) with stirring under dry argon at 5–10 °C. Stirring was continued for 2–3 h at room temperature, and then water (50 ml) was added.The organic layer was separated, dried with CaCl2 and concentrated. The residue was chromatographed on a plate with neutral alumina (Brockmann activity III) in hexane. Thermolysis of 3-alkyl-3-ferrocenylcyclopropenes 1a–c. A solution of 1 mmol of cyclopropenes 1a–c in 50 ml of dry benzene was boiled for 3–5 h until the disappearance of the initial cyclopropenes (TLC, hexane).Following the removal of the solvent, the residue was subjected to preparative TLC on silica gel (hexane). Reaction of cyclopropenes 1b,c with 1,3-diphenylisobenzofuran. A solution of 0.56 g (2 mmol) of DPIBF and of 0.41 g (1.5 mmol) of cyclopropenes 1b,c in 60 ml of dry benzene was refluxed for 5 h (monitoring by TLC on silica gel, as in the previous experiment).Then, the solvent was removed, and TLC on SiO2 (hexane–benzene, 2:1) was carried out. The following compounds were separated: 1,3-dihydro-1,3- diphenylisobenzofuran 4,9 alkenes 5b,c, propynes 3b,c, vinyl ketones 6b,c and Diels–Alder adducts 7b,c (mixture of isomers, 3 :1). Reaction of propyne 3a with 1,3-diphenylisobenzofuran. A mixture of 3-ferrocenylbut-3-ene-1-yne 3a (0.24 g, 1 mmol) and 1,3-isobenzofuran (0.27 g, 1 mmol) in 50 ml of dry benzene was stirred at room temperature for 10 h.Then, the solvent was removed in a vacuum, and TLC on SiO2 (hexane–benzene, 2:1) was carried out. The following compounds were separated: endo-2a, Rf = 0.27, yield 46%, mp 205 °C; exo-2b, Rf = 0.32, yield 22%, mp 195–196 °C.9 and in the generation of enynes 3a–c. Further, we have found that ButOK in THF, unlike ButOK in DMSO,4,10,11 is a convenient reagent1 for the preparation of ferrocenylvinylacetylenes from corresponding gem-dibromocyclopropanes 9a–c,§§ the yields of acetylenes 3a–c can be as high as 52–63%.†† However, the formation of methyl vinyl ketones 6a–c (8–15%) during isolation and purification cannot be avoided: The reaction seems to occur via intermediate 3-alkyl-1- bromo-3-ferrocenylcyclopropenes 10a–c, although these cannot be captured when the reaction was carried out in the presence of 1,3-dienes.‡‡ 7b1: Rf = 0.29 (hexane–benzene, 2:1), yield 34%, yellow crystals, mp 226–227 °C. 1H NMR, d: 0.39 (d, 6H, Me, J 6.68 Hz), 2.45 (s, 2H, CH), 2.95 (m, 1H, CH, J 6.68 Hz), 4.07 (s, 5H, C5H5), 3.91 (s, 4H, C5H4), 6.95–7.83 (m, 14H, 3Ar).Found (%): C, 80.42; H, 5.94; Fe, 10.54. Calc. for C36H32FeO (%): C, 80.60; H, 6.01; Fe, 10.41. 7b2: Rf = 0.19 (hexane–benzene, 2:1), yield 10%, yellow crystals, mp 234–235 °C. 1H NMR, d: 0.42 (d, 6H, Me, J 6.7 Hz), 2.40 (s, 2H, CH), 2.72 (m, 1H, CH, J 6.7 Hz), 3.97 (s, 5H, C5H5), 4.11 (s, 4H, C5H4), 7.05–7.81 (m, 14H, 3Ar). Found (%): C, 80.76; H, 6.24; Fe, 10.18. Calc.for C36H32FeO (%): C, 80.60; H, 6.01; Fe, 10.41. 7c1: Rf = 0.32 (hexane–benzene, 2:1), yield 36%, yellow crystals, mp 218–219 °C. 1HNMR, d: 1.42–2.05 (m, 6H, CH2), 2.41 (s, 2H, CH), 2.92 (m, 1H, CH), 4.05 (s, 5H, C5H5), 4.01 (s, 4H, C5H4), 7.00–7.91 (m, 14H, 3Ar). Found (%): C, 80.93; H, 5.65; Fe, 10.23. Calc. for C37H32FeO (%): C, 81.02; H, 5.88; Fe, 10.18. 7c2: Rf = 0.32 (hexane–benzene, 2:1), yield 11%, yellow crystals, mp 231–232 °C. 1H NMR, d: 1.75–2.35 (m, 6H, CH2), 2.46 (s, 2H, CH), 3.15 (m, 1H, CH), 4.08 (s, 5H, C5H5), 3.94 (m, 2H, C5H4), 4.04 (m, 2H, C5H4), 7.15–7.76 (m, 14H, 3Ar). Found (%): C, 81.14; H, 5.92; Fe, 10.19. Calc. for C37H32FeO (%): C, 81.02; H, 5.88; Fe, 10.18. §§ 9b: yield 74%, orange crystals, mp 123–124 °C. 1H NMR, d: 0.98 (d, 3H, Me, J 6.8 Hz), 1.15 (d, 3H, Me, J 6.8 Hz), 1.75 (d, 1H, CH2, J 7.2 Hz), 2.11 (d, 1H, CH2, J 7.2 Hz), 2.17 (m, 1H, CH), 4.16 (s, 5H, C5H5), 4.21 (m, 2H, C5H4), 4.25 (m, 2H, C5H4).Found (%): C, 44.85; H, 4.34; Fe, 13.70; Br, 37.63. Calc. for C16H18Br2Fe (%): C, 45.09; H, 4.26; Fe, 13.10; Br, 37.55. 9c: yield 72%, orange crystals, mp 127–128 °C. 1H NMR, d: 1.56 (s, 1H, CH2), 1.87 (s, 1H, CH2), 1.70–2.55 (m, 6H, CH2), 2.58 (m, 1H, CH), 4.15 (s, 5H, C5H5), 3.46 (m, 1H, C5H4), 4.03 (m, 1H, C5H4), 4.13 (m, 1H, C5H4), 4.21 (m, 1H, C5H4).Found (%): C, 46.71; H, 4.28; Fe, 12.52; Br, 36.63. Calc. for C17H18Br2Fe (%): C, 46.60; H, 4.14; Fe, 12.74; Br, 36.52. 2[1b,c] D H H Fc C R H R CHR2 Fc H 8b,c 3b,c + 5b,c C Fc H R R 1b,c CH Fc R R Ph Ph O Fc C C C R R CH C C H R R Fc C Me H Fc C C C R R Me O D D DPIBF 7b,c 48% 3b,c 16% 4 7% 5b,c 8% 6b,c 3–6% 3b,c 23% 5b,c 30% 6b,c 5% b R = Me c R + R = (CH2)3 Fc C Br Br R H R 9a–c Fc C Br R H R 10a–c ButOK THF 3a–c + 6a–c a R = H b R = Me c R + R = (CH2)3Mendeleev Communications Electronic Version, Issue 6, 1999 (pp. 213–255) Further, we have found that 3-ferrocenyl-4-methylpent-3- en-1-yne 3b and 3-cyclobutylidene-3-ferrocenylpropyne 3c, respectively, do not react with DPIBF even on refluxing in m-xylene. This is in contrast to the behaviour of 3-ferrocenylbut- 3-en-1-yne 3a,‡ which gave a Diels–Alder adduct as a mixture of endo- and exo-isomers (2a:2b ~ 2:1) in an almost quantitative yield.9 a-Ferrocenylvinylacetylenes 3a–c readily add water upon dissolution in wet solvents and upon chromatographing on alumina (Brockmann activity III).When stored under ordinary conditions, they undergo rapid polymerization and resinification. References 1 W. M. Horspool, R. G. Sutherland and B. J. Thomson, J. Chem. Soc. (C), 1971, 1554. 2 W. M. Horspool, R. G. Sutherland and B. J. Thomson, J. Chem. Soc. (C), 1971, 1558. 3 W. M. Horspool, R. G. Sutherland and B. J. Thomson, J. Chem. Soc. (C), 1971, 1563. 4 E. I. Klimova, N. N. Meleshonkova, T. B. Klimova, M. G. Martinez and C. T. Alvarez, Mendeleev Commun., 1997, 242. 5 A. J. Fray, P. S. Jain and R. L. Krieger, J. Organomet. Chem., 1981, 214, 381. 6 A. J. Fray, R. L. Krieger, I. Agranat and E. Aharon-Shalom, Tetrahedron Lett., 1976, 32, 4803. 7 E. I. Klimova, T. B. Klimova, L. Ruiz Ramirez, M. G. Martinez, C. T. Alvarez, P. G. Espinova and A R. Toscano, J. Organomet. Chem., 1997, 545, 191. 8 E. I. Klimova, M. G. Martinez, T. B. Klimova, C. T. Alvarez, Ar R. Toscano, R. Moreno Esparza and L. Ruiz Ramirez, J. Organomet. Chem., 1998, 566, 175. 9 E. I. Klimova, L. Ruiz Ramirez, T. B. Klimova, M. G. Martinez, N. N. Meleshonkova and A. V. Churakov, J. Organomet. Chem., 1998, 559, 1. 10 T. C. Shields and W. E. Billups, Chem. Ind., 1967, 25, 1999. 11 T. C. Shields, W. E. Billups and A. N. Kurtz, Angew. Chem., Int. Ed. Engl., 1968, 7, 209. Received: 2nd June 1999; Com. 99/1509