4858 Organometallics 1996, 14, 4858-4864 Rhodium-AssistedTransformations of Substituted Thiophenes into Butadienyl Methyl Sulfides Claudio Bianchini," M. Victoria Jimbnez, Andrea Meli, and Francesco Vizza Istituto per zyxwvutsrqp lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione, ISSECC-CNR, Via J. Nardi 39, 50132 Firenze, Italy Received May 25, 1 9 9 6 The novel butadienethiolate complex zyxwvu (triphos)Rh(y3-SC(Tyl)=CHCH=CH2I (Tyl= thieny1)- has been prepared by reaction of (triphos)RhH3 with 2,Y-bithiophene (2-TylT) in refluxing tetrahydrofinan (THF) (triphos zyxwvut = MeC(CH2PPh2)3). Insertion of rhodium occurs exclusively at the C-S bond of a thienyl group of TylT distal to the other thienyl. Complexes of l-(methylthio)buta-l,3-diene with the formula [(triphos)Rh( y3-MeSCR=CRCH=CH2)lBPb have been prepared by treatment of the corresponding butadienethiolate complexes (triphod- Rh(y3-SCR=CRCH=CH2) (R = H, R = Me, COMe, COzEt, Tyl; R = H, R = Me, COMe, OMe) with MeI, followed by a metathetical reaction with NaBPh4. The Rh thioether complexes react with CO zyxwvut (5 atm, 70 "C) in THF to give free butadienyl methyl sulfides zy (2)- MeSCR-CRCH-CH2 and, quantitatively, the dicarbonyl complex [(triphos)Rh(C0)2lBPL. The butadienyl methyl sulfides have been purified by LC and characterized by their NMR and MS properties. Inter alia, the chemistry presented herein provides a novel entry into the synthesis of substituted-butadienylmethyl sulfides, for which a general methodology is still lacking. Introduction Scheme 1 Thiophene (T) is a molecule of substantial interest for its extraordinarily wide range of chemical applications. Organic chemists largely use T as a precursor to a variety of products via electrophilic attack (nitration, halogenation, sulfonation, acylation, alkylation, etc.), often followed by desulfuration (e. g., synthesis of long- chain alkanes).' More recent and sophisticated applica- tions span the use of T as a model compound to study the mechanism of the hydrodesulfurization (HDS) reac- tion of fossil fuels: the preparation of new materials with unusual physical properties (ele~trical,~ magnetic: nonlinear optical5),and the synthesis of complex mol- ecules of biological importance.6 We have recently shown that T can efficiently be used for the synthesis of conjugated organosulfur compounds via metal-promoted C-S bond cleavage, followed by electrophilic attack and ~arbonylation.~ Scheme 1 il- @Abstract published in Advance ACS Abstmcts, September 15,1995. (1) March, J. Advances Organic Chemistry, 4th ed.; Wiley: New York, 1992. (2) (a)Angelici, R. J. In Encyclopedia of Inorganic Chemistry; King, R. B., Ed.; Wiley: New York, 1994;Vol. 3, p 1433. (b) Sbnchez-Delgado, R. A. J. Mol. Catal. 1994, 86, 287. (c) Wiegand, B. C.; Friend, C. M. Chem. Reu. 1992, 92, 491. (d) Girgis, M. J.; Gates, B. C. Ind. Eng. Chem. Res. 1991, 30, 2021. (e) Rauchfuss, T. B. Prog. Inorg. Chem. 1991, 39, 259. zyxwvutsrqpon (0 Angelici, R. J. Coord. Chem. Rev. 1990, 105, 61. (g) Prins, R.; deBeer, V. H. J.; Somorjai, G. A. Catal. Rev.-Sci. Eng. 1989, 31, 1. (h) Friend, C. M.; Roberts, J. T. Acc. Chem. Res. 1988,21, 394. (i) Angelici, R. J. Acc. Chem. Res. 1988, 21, 387. (3) (a) Graf, D. D.; Day, N. C.; Mann, K. R. Inorg. Chem. 1995,34, 1562. (b) Shaver, A.; Butler, I. S.; Gao, J. P. Organometallics 1989,8, 2079. (c) Tour, J. M.; Wu, R.; Schumm, J. J. Am. Chem. SOC. 1991, 113, 7064. (4)Mitsumori, T.; Inoue, K.; Koga, N.; Iwamura, H. J. Am. Chem. SOC. 1995, 117, 2067. (5)Long, N. J. Angew. Chem., Int. Ed. Engl. 1996,34, 21. (6) (a)Jaouhari, R.; GuBnot, P.;Dixneuf, P. H. J. Chem. SOC., Chem. Commun. 1986, 1255. (b) Nicolau, K. C.; Renaud, J.; Nantermet, P. G.; Couladouros, E. A.; Guy, R. K.; Wrasidlo, W. J. Am. Chem. SOC. 1995, 117,2409. lustrates the procedure for the preparation of butadienyl methyl sulfide. The success of this method has inspired us to inves- tigate alternative methods of synthesizing butadienyl methyl sulfides bearing various substituents in the butadienyl moiety. Such a,B,y,d-unsaturated sulfides are, in fact, generally difficult to prepare using standard organic chemistry procedures,8 even though they are excellent starting materials for further structural elabo- rations (Diels-Alder additions, reductions, oxidation of either the sulfur or the double bond, polymerization89 as well as molecules endowed with a specific activity (nonlinear optical, radicophilic5J0). The first step of our investigation was to determine whether the 16-electron fragment [(triphos)RhHl,gen- (7) Bianchini, C.; Frediani, P.; Herrera, V; Jimenez, M. V.; Meli, A.; Rincbn, L.; Sbnchez-Delgado, R. A.; Vizza, F. J. Am. Chem. SOC. 1995, 117, 4333. 0276-733319512314-4858$09.00/0 0 1995 American Chemical Society