RHODIUM-ASSISTED TRANSFORMATIONS OF SUBSTITUTED THIOPHENES INTO BUTADIENYL METHYL SULFIDES

The novel butadienethiolate complex (triphos)Rh(eta(3)-SC(Tyl)=CHCH=CH2) (Tyl = thienyl)-has been prepared by reaction of(triphos)RhH3 with 2,2'-bithiophene (2-TylT) in refluxing tetrahydrofuran (THF) (triphos MeC(CH(2)PPh(2))(3)). Insertion of rhodium occurs exclusively at the C-S bond of a thienyl group of TylT distal to the other thienyl. Complexes of 1-(methylthio)buta-1,3-diene with the formula [(triphos)Rh(eta(3)-MeSCR-CR'CH=CH2)]BPh(4) have been prepared by treatment of the corresponding butadienethiolate complexes (triphos)-Rh(eta(3)-SCR=CR'CH=CH2) (R' = H, R = Me, COMe, CO(2)Et, Tyl; R = H, R' = Me, COMe, OMe) with MeI, followed by a metathetical reaction with NaBPh(4). The Rh thioether complexes read with CO (5 atm, 70 degrees C) in THF to give free butadienyl methyl sulfides (Z)-MeSCR=CR'CH=CH2 and, quantitatively, the dicarbonyl complex [(triphos)Rh(CO)(2)] BPh(4). 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-butadienyl methyl sulfides, for which a general methodology is still lacking.