947735-24-2Relevant academic research and scientific papers
Insertion of alkynes into an ArS-Pt bond: Regio- and stereoselective thermal reactions, facilitation by "o-halogen effect" and photoirradiation, different alkyne preferences depending on the ancillary ligand, and application to a catalytic reaction
Kuniyasu, Hitoshi,Takekawa, Kazunobu,Yamashita, Fumikazu,Miyafuji, Kiyoshi,Asano, Shigehito,Takai, Yasutomo,Ohtaka, Atsushi,Tanaka, Aoi,Sugoh, Kunihiko,Kurosawa, Hideo,Kambe, Nobuaki
, p. 4788 - 4802 (2009/02/08)
The insertion of alkyne 2 into the S-Pt bond(s) of Pt(SAr)(Cl)(PPh 3)2 (7), Pt(SAr)2(PPh3)2 (8), and Pt(SAr)(Ar′)(dppe) (9) has been investigated. Regioselective c/s-insertion into the S-Pt bond of trans-7 took place with terminal and internal alkynes (RC≡CR′; R′ = H, C(O)OEt, and CH 2OMe) at 70-110 °C to give Pt[(Z)-C(R′)=C(SAr)R](Cl) (PPh3)2 (Z-10) as stable compounds. The introduction of an electron-donating group in Ar of ArC≡CH and in ArS of 7 slightly facilitated the reactions. It was found that a halogen atom at the ortho position in ArS of 7 dramatically promoted the insertion ("o-halogen effect"). The insertion of a terminal alkyne (2, RC≡CH) into the S-Pt bond of trans-Pt(SAr)2(PPh3)2 (8) also occurred to afford Pt[(Z)-C(H)=C(SAr)R](SAr)(PPh3)2 (Z-16), which was further converted into Pt(PPh3) 2(RC≡CH) (18) and (Z,Z)-(ArS)(R)C=C(H)-C(H)=C(SAr)(R) (19) by C-C bond-forming reductive elimination after the insertion of another 2 into the remaining S-Pt bond of 16. The "o-halogen effect" was also observed for the insertion of 2 into the S-Pt bond of trans-8 to furnish the corresponding cis-Z-16 as a kinetic product; the trans-isomer of 8 exhibited a higher reactivity than the cis-isomer. It was also revealed that photoirradiation (visible light) dramatically promoted the insertion of 2 into the S-Pt bond of trans-8. Photoinduced insertion was facilitated by introducing an electron-donating group into Ar of ArC≡CH. Contrary to the cases of PPh3-ligated platinum complexes, the insertion into the S-Pt bond of Pt(SAr)(Ar′)(dppe) (9) was realized when the electron-deficient alkyne DMAD (2t) was employed as a substrate. Also presented is the insertion of two alkynes into each S-Pt bond of 8 in the Pt-catalyzed stereo- and regioselective dimerization-bisthiolation of alkyne (2) by diaryl disulfide ((ArS)2, 30) to yield functionalized symmetrical 1,3-dienes.
Definitive evidence for the insertion of terminal alkynes into ArylS-Pt bonds: "o-halogen effect" in stoichiometric and catalytic reactions
Kuniyasu, Hitoshi,Yamashita, Fumikazu,Terao, Jun,Kambe, Nobuaki
, p. 5929 - 5933 (2008/09/16)
(Chemical Equation Presented) An unexpected acceleration of the insertion of terminal alkynes into the S-Pt bond of complexes 1 was observed when an o-halogen substituent was present in the SAr moiety (see scheme). The reaction rates for G = o-Cl, o-Br, or o-l were much greater than for electron-donating or electron-withdrawing groups. This "o-halogen effect" was also found to be relevant to the Pd-catalyzed addition of (ArS)2 to alkynes.
