J. Org. Chem. 2000, 65, 1721-1728
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Preparation and Reactivity of 1,3-Bis(alkylthio)allenes and Tetrathiacyclic Bisallenes Toshio Shimizu, Kensuke Sakamaki, Daisuke Miyasaka, and Nobumasa Kamigata* Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan Received October 7, 1999
Reactions of Ph2C3 dianion, prepared from 1,3-diphenylpropyne and n-butyllithium, with alkyl thiocyanates or alkane dithiocyanates gave 1,3-bis(alkylthio)allenes 1 or tetrathiacyclic bisallenes 2, respectively. Thermal reactions of 1 gave thiophenes 4 and 7, benzothiepin 5, 1,2-bis(benzylidene)cyclobutane 6, thiete 8, and R,β-unsaturated ketone 9, and the reactions of tetrathiacyclic bisallenes 2a gave a cyclic dimer, 1,2-bis(benzylidene)cyclobutane derivative 10, quantitatively. Irradiation of 1,3-bis(alkylthio)allenes 1 and tetrathiacyclic bisallenes 2a caused rearrangement to give alkynes 18, 20, and 21. In the irradiation of the cyclic bisallenes 2a, isomerizations from dl to meso and meso to dl isomers were also found. In the reactions of allenes 1 and cyclic bisallenes 2a with diphenyl diazomethane, the diazomethane reacted selectively with the double bond rather than with the sulfur atom. Introduction
Scheme 1
Allenes are reactive species with cumulated double bonds and are useful intermediates for organic synthesis. Many studies have been performed on their preparation and reactivity.1-3 Allenes substituted by heteroatoms, such as silicon, phosphorus, and sulfur atoms, have also received attention.3 Among the sulfur-substituted allenes, mono-,4,5 1,1-bis-,6 tris-,7 and tetrakis(alkylthio)allenes7 were synthesized in the 1960s. However, few of their reactivities have been clarified, except for isomerization between the allenes and acetylenes. We succeeded in preparing 1,3-bis(alkylthio)allenes by reacting Ph2C3 dianion with the corresponding alkyl thiocyanates, and the introduction of alkylthio groups to the 1- and 3-positions of allenes was found to strongly influence their reactivities. It has also been found that the thermal reactions of 1,3-bis(alkylthio)allenes gave thiophene, benzothiepin, cyclobutane, thiete, and R,β-unsaturated ketone derivatives. In this paper, we report the preparation and some reactivities, such as the thermal reaction, photochemical * To whom correspondence should be addressed. Tel: +81 (426) 772556. Fax: +81 (426) 77-2525. E-mail:
[email protected]. (1) For reviews, see: (a) Smadja, W. Chem. Rev. 1983, 83, 263. (b) The Chemistry of the Allenes; Landor, S. R., Ed.; Academic Press: New York, 1982; Vols. 1-3. (c) Brandsma, L.; Verkruijsee, H. D. Synthesis of Acetylenes, Allenes and Cumulenes; Elsevier: New York, 1980. (d) The Chemistry of Ketenes, Allenes and Related Compounds; Patai, S., Ed.; Wiley: New York, 1980; Vols. 1 and 2. (e) Huche´, M. Tetrahedron 1980, 36, 331. (f) Mavrov, M. V.; Kucherov, V. F. Russ. Chem. Rev. 1967, 36, 233. (2) For reviews, see: (a) Pasto, D. J. Tetrahedron 1984, 40, 2805. (b) Baldwin, J. E.; Fleming, R. H. Fortschr. Chem. Forsch. 1970, 15, 281. (c) Taylor, D. R. Chem. Rev. 1967, 67, 317. (3) For reviews, see: (a) Bruneau, C.; Dixneuf, P. H. Compr. Org. Funct. Group Transform. 1995, 1, 953. (b) Marshall, J. A. Chem. Rev. 1996, 96, 31. (c) Schuster, H. F.; Coppola, G. M. Allenes in Organic Synthesis; Wiley: New York, 1984; and references therein. (4) (a) Pourcelot, G.; Cadiot, P.; Willemart, A. Compt. Rend. Acad. Sci. 1961, 252, 1630. (b) Pourcelot, G.; Le Quan, M.; Simonnin, M.-P.; Cadiot, P. Bull. Soc. Chim. Fr. 1962, 1278. (5) Brandsma, L.; Wijers, H. E.; Arens, J. F. Rec. Trav. Chim. PaysBas 1963, 82, 1040. (6) Wildschut, G. A.; van Boom, J. H.; Brandsma, L.; Arens, J. F. Rec. Trav. Chim. Pays-Bas 1968, 87, 1447. (7) Wildschut, G. A.; Brandsma, L.; Arens, J. F. Rec. Trav. Chim. Pays-Bas 1969, 88, 1132.
reaction, and reaction with diphenyl diazomethane, of 1,3-bis(alkylthio)allenes and tetrathiacyclic bisallenes.8 Results and Discussion Preparation of 1,3-Bis(alkylthio)allenes and Tetrathiacyclic Bisallenes. When a THF solution of 2 equiv of methyl thiocyanate was added dropwise to Ph2C3 dianion (1,3-dilithiated allene), prepared from 1,3-diphenylpropyne and n-butyllithium in ether/THF solution,9 at -80 °C and allowed to warm to room temperature, 1,3bis(methylthio)-1,3-diphenylpropadiene (1a) was obtained in 62% yield (Scheme 1). A similar reaction of the (8) For a preliminary communication, see: Shimizu, T.; Sakamaki, K.; Kamigata, N. Tetrahedron Lett. 1997, 38, 8529. (9) (a) Klein, J.; Backer, J. Y. J. Chem. Soc., Chem. Commun. 1973, 576. (b) Leroux, Y.; Mantione, R. Tetrahedron Lett. 1971, 591.
10.1021/jo9915675 CCC: $19.00 © 2000 American Chemical Society Published on Web 03/02/2000
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J. Org. Chem., Vol. 65, No. 6, 2000
Figure 1. Crystal structure of meso-2a showing 50% probability displacement ellipsoids with hydrogen atoms removed for clarity; selected bond lengths (Å) and bond angles (deg): S(1)-C(1), 1.7753(7); C(1)-C(2), 1.3095(8); C(2)-C(3*), 1.3162(8); S(2*)-C(3*), 1.7873(7); S(1)-C(1)-C(2), 122.26(6); C(1)C(2)-C(3*), 175.73(9); S(2*)-C(3*)-C(2), 117.85(6).
dianion with benzyl thiocyanate gave 1,3-bis(benzylthio)1,3-diphenylpropadiene (1b) in 88% yield. 3,3-Bis(alkylthio)-1,3-diphenylpropyne, the formation of which is also anticipated from the reaction, was not obtained in either reaction, whereas reaction of the Ph2C3 dianion with ethyl bromide under similar conditions yielded 3,3-diethyl-1,3diphenylpropyne in 63% yield together with 14% of the 1,3-diethyl-1,3-diphenylpropadiene. Reaction of the Ph2C3 dianion with ethane 1,2-dithiocyanate formed 14-membered cyclic bisallene 2a in 21% yield (dl/meso ) 41/59), although the reaction with methylene dithiocyanate did not give the corresponding cyclic bisallene. The stereochemistry of one isomer of the cyclic bisallenes, meso-2a, was determined by X-ray crystallographic analysis, as shown in Figure 1.8 The bond lengths are almost normal, and the bond angle C(1)-C(2)-C(3*) and torsion angle S(1)-C(1)-C(3*)S(2*) are 176 and 94°, respectively, indicating a strainfree geometry. Similarly, larger sulfur-substituted cyclic bisallenes 2b-e were also obtained in yields of 25% (dl/ meso ) 64/36), 20% (dl/meso ) 75/25), 14% (dl/meso ) 24/76), and 13% (dl/meso ) 67/33), respectively, by reacting the dianion with corresponding alkane dithiocyanates. The structures and the ratios of the dl- and meso-isomers of 2b-e were estimated by comparison of their 13C NMR spectra with those of dl- and meso-2a. Cyclic monoallenes, which were expected to be formed when using longer alkane dithiocyanates, were not obtained in any of the reactions, whereas the reaction of the dianion with 1,8-dibromooctane gave 1,3-diphenylundeca-1,2-diene although the yield was low (7% yield). The lack of formation of the cyclic monoallene is perhaps due to the conformation in the ring-closure reaction because the reaction of the dianion with 0.5 equiv of methyl thiocyanate gave a ca. 1:1 mixture of the mono(methylthio)allene and the bis(methylthio)allene, and this result indicates that the reactivity of the anion 3 is not low.
Shimizu et al.
Thermal Reaction of 1,3-Bis(alkylthio)allenes and Tetrathiacyclic Bisallenes. Cyclodimerization reactions of allenes are well-known,2,10,11 and tetrakis(methylthio)allene7 and 1,1-bis(alkylthio)allene12 have also been reported to undergo dimerization even at room temperature to give cyclic dimers. However, 1,3-bis(methylthio)allene 1a and 1,3-bis(benzylthio)allene 1b were stable at room temperature. When a p-xylene solution of 1a was refluxed for 3 days, 68% of 1a was consumed and 2,4-diphenyl thiophene (4),13 1,3-dihydro2-benzothiepin 5, and 1,2-bis(methylthiobenzylidene)cyclobutane 6 were obtained in 30, 18, and 8% yields, respectively (Scheme 2). The position of the double bond for the thiepin ring of 5 was determined by HMBC NMR measurements. A stereoisomer of 6 was also obtained in this reaction in 8% yield, which showed C2 or Cs symmetry on 1H and 13C NMR spectra, although the stereochemistry could not be clarified. The stereochemistry of 6 was determined by X-ray crystallographic analysis, as shown in Figure 2, which showed a trans geometry for the two methylthio groups on the cyclobutane ring and a cis geometry for the olefins. In addition, the crystal was found to be racemic and the cyclobutane ring was nearly planar; dihedral angles in the ring were 4.2-4.6°. 1,3Bis(benzylthio)allene 1b also readily underwent a thermal reaction to give 2,3,5-triphenylthiophene (7),14 thiete 8, and R,β-unsaturated ketone 9 in 63, 5, and 11% yields, respectively, under reflux in p-xylene for 1 h. It is clear that the thermal reaction of 1,3-bis(alkylthio)allenes is affected by the substituents on the sulfur atoms. The thermal reaction of cyclic bisallene dl-2a caused intramolecular cyclization, rather than other reactions found in the case of compounds 1, to give tricyclic compound 10 in quantitative yield. The isomer meso-2a also gave an identical compound stereoselectively and quantitatively under similar conditions. In both cases, head-to-head cycloadduct 10 was obtained with the same (10) For examples, see: (a) Lebedev, S. V. J. Russ. Phys. Chem. Soc. 1913, 45, 1249; Chem. Abstr. 1914, 8, 320. (b) Blomquist, A. T.; Verdol, J. A. J. Am. Chem. Soc. 1956, 78, 109. (c) Williams, J. K.; Sharkey, W. H. J. Am. Chem. Soc. 1959, 81, 4269. (d) Pilgram, K.; Korte, F. Tetrahedron Lett. 1962, 883. (e) Roedig, A.; Bischoff, F.; Heinrich, B.; Markl, G. Ann. Chem. 1963, 670, 8. (f) Slobodin, Y. M.; Khitrov, A. P. J. Gen. Chem. USSR 1963, 33, 146. (g) Slobodin, Y. M.; Khitrov, A. P. J. Gen. Chem. USSR 1963, 33, 2748. (h) Roedig, A.; Detzer, N.; Friedrich, H. J. Angew. Chem. 1964, 76, 379. (i) Fischer, H.; Fischer, H. Chem. Ber. 1964, 97, 2975. (j) Banks, R. E.; Haszeldine, R. N.; Taylor, D. R. J. Chem. Soc. 1965, 978. (k) Skattebøl, L.; Solomon, S. J. Am. Chem. Soc. 1965, 87, 4506. (l) Gajewski, J. J.; Shih, C. N. J. Am. Chem. Soc. 1969, 91, 5900. (m) Jacobs, T. L.; McClenon, J. R.; Muscio, O. J., Jr. J. Am. Chem. Soc. 1969, 91, 6038. (n) Gajewski, J. J.; Black, W. A. Tetrahedron Lett. 1970, 899. (o) Jacobs, T. L.; Muscio, O. J., Jr. Tetrahedron Lett. 1970, 4829. (p) Dolbier, W. R., Jr.; Dai, S.-H. J. Am. Chem. Soc. 1970, 92, 1774. (q) Gajewski, J. J.; Shih, C. N. J. Org. Chem. 1972, 37, 64. (r) Dai, S.-H.; Dolbier, W. R., Jr. J. Am. Chem. Soc. 1972, 94, 3946. (11) (a) Roberts, J. D.; Sharts, C. M. Org. React. 1962, 12, 1. (b) Moore, W. R.; Mogolesko, P. D.; Traficante, D. D. J. Am. Chem. Soc. 1972, 94, 4753. (c) Levek, T. J.; Kiefer, E. F. J. Am. Chem. Soc. 1976, 98, 1875. (d) Becher, G.; Skattebøl, L. Tetrahedron Lett. 1979, 1261. (12) Minami, T.; Okauchi, T.; Matsuki, H.; Nakamura, M.; Ichikawa, J.; Ishida, M. J. Org. Chem. 1996, 61, 8132. (13) Wynberg, H.; van Driel, H.; Kellogg, R. M.; Buter, J. J. Am. Chem. Soc. 1967, 89, 3487. (14) (a) Smith, A. J. Chem. Soc. 1890, 57, 647. (b) Mitra, S. K. J. Indian Chem. Soc. 1938, 15, 59. (c) Karakasa, T.; Takeda, S.; Saito, T.; Motoki, S. Bull. Chem. Soc. Jpn. 1986, 59, 3279.
1,3-Bis(alkylthio)allenes and Tetrathiacyclic Bisallenes
Figure 2. Crystal structure of 6 showing 50% probability displacement ellipsoids with hydrogen atoms removed for clarity; selected bond lengths (Å), bond angles (deg) and dihedral angles (deg): C(1)-C(1*), 1.620(4); C(1)-C(2), 1.533(4); C(2)-C(2*), 1.467(4); C(1)-S(1), 1.851(4); C(1)-C(3), 1.520(5); C(2)-C(4), 1.356(4); C(1*)-C(1)-C(2), 87.1(2); C(1)-C(2)C(2*), 92.8(2); C(1*)-C(1)-C(3), 115.5(3); C(2)-C(1)-C(3), 119.2(3); C(2)-C(1)-S(1), 114.7(3); C(1)-C(2)-C(4), 129.1(3); C(2*)-C(2)-C(4), 137.6(3); C(2)-C(1)-C(1*)-C(2*), 4.2(3); C(1*)-C(1)-C(2)-C(2*), -4.3(3); C(1)-C(2)-C(2*)-C(1*), 4.6(3); C(3)-C(1)-C(1*)-C(3*), 121.9(3); S(1)-C(1)-C(1*)-S(1*), -123.4(2); C(4)-C(2)-C(2*)-C(4*), 21.2 (9).
Scheme 2
stereochemistry, and the crystal structure of tricyclic compound 10 is given in Figure 3. The crystal structure showed that the ethane dithiolate was fused to the cyclobutane ring with cis geometry, in contrast to that of 6. The cyclobutane ring had a nonplanar geometry; dihedral angles in the ring were 14.7-16.4°. The geometries of olefin moieties were trans, and the two double bonds were not conjugated; dihedral angle C(5)-C(2)C(3)-C(6) ) -36°.
J. Org. Chem., Vol. 65, No. 6, 2000 1723
Figure 3. Crystal structure of 10 showing 50% probability displacement ellipsoids with hydrogen atoms removed for clarity; selected bond lengths (Å), bond angles (deg), and dihedral angles (deg): C(1)-C(2), 1.535(9); C(1)-C(4), 1.63(1); C(2)-C(3), 1.46(1); C(3)-C(4), 1.544(9); C(1)-S(1), 1.852(7); C(2)-C(5), 1.33(1); C(3)-C(6), 1.34(1); C(4)-S(2), 1.812(8); C(2)-C(1)-C(4), 85.4(5); C(1)-C(2)-C(3), 92.9(5); C(2)-C(3)C(4), 91.0(5); C(1)-C(4)-C(3), 86.4(5); C(4)-C(1)-C(2)-C(3), 15.5(5); C(2)-C(1)-C(4)-C(3), -14.7(5); C(1)-C(2)-C(3)C(4), -16.4(6); C(2)-C(3)-C(4)-C(1), 15.4(5); S(1)-C(1)C(4)-S(2), -21.2(6); C(5)-C(2)-C(3)-C(6), -36(1).
To examine the reaction mechanism, the thermal reaction of 1a was carried out in the presence of 1.5 equiv of 1,1-diphenyl-2-picryl hydrazyl (DPPH). After refluxing for 3 days, compounds 4, 5, and 6, which were obtained by the thermal reaction of 1a, were not detected. In the case of 1b, addition of 2.5 equiv of DPPH also inhibited the formation of 8 ( 3σ(I) were used in the leastsquares refinement to yield R ) 0.037 and Rw ) 0.039. Compound 6. A yellow needle of C34H32S4 having approximate dimension of 0.50 × 0.40 × 0.40 mm3. Monoclinic space group P2/a with a ) 18.064(5) Å, b ) 11.274(2) Å, c ) 16.359(3) Å, β ) 116.62(2)°, V ) 2978(1) Å3, Z ) 4, and F(calcd) ) 1.266 g cm-3. Of the 6278 unique data, the 4624 with I > 3σ(I) were used in the least-squares refinement to yield R ) 0.052 and Rw ) 0.053. Compound 10. A yellow plate of C34H28S4 having approximate dimension of 0.40 × 0.30 × 0.15 mm3. Orthorhombic space group P212121 with a ) 9.803(2) Å, b ) 32.311(8) Å, c ) 8.859(2) Å, V ) 2806(1) Å3, Z ) 4, and F(calcd) ) 1.336 g cm-3. Of the 3351 unique data, the 2412 with I > 3σ(I) were used in the least-squares refinement to yield R ) 0.057 and Rw ) 0.063. Compound 25. A yellow prism of C30H26S2 having approximate dimension of 0.60 × 0.30 × 0.25 mm3. Monoclinic space group P21/n with a ) 12.994(3) Å, b ) 18.214(3) Å, c ) 10.907(2) Å, β ) 107.68(1)°, V ) 2459.5(7) Å3, Z ) 4, and F(calcd) ) 1.217 g cm-3. Of the 2679 unique data, the 2481 with I > 3σ(I) were used in the least-squares refinement to yield R ) 0.060 and Rw ) 0.108.
Acknowledgment. This work was financially supported in part by a Grant-in-Aid for Scientific Research on Priority Area and General Scientific Research from the Ministry of Education, Science, Sports, and Culture, Japan. Supporting Information Available: Detailed information of the X-ray crystallographic analysis of 6, 10, and 25 including structure diagrams, details of data collection and reduction and structure solution and refinement, tables of positional and thermal parameters, and bond lengths, angles, and torsional angles. This material is available free of charge via the Internet at http://pubs.acs.org. JO9915675
