27758-94-7Relevant articles and documents
Aminophosphine palladium pincer complexes for Suzuki and Heck reactions
Bolliger, Jeanne L.,Frech, Christian M.
scheme or table, p. 23 - 28 (2010/04/24)
The aminophosphine-based pincer complexes [C6H 3-2,6-{NHP(piperidinyl)2}2Pd(CI)] (2) and [C6H3-2,6-{OP(piperidinyl)2}2Pd(CI)] (3) are readily prepared from cheap starting materials by sequential addition of 1,1′,1 "-phosphinetriyltripiperidine and 1,3-diaminobenzene or resorcinol to solutions of [Pd(cod)(CI)2] (cod = cyclooctadiene) in toluene under N2 in 'one pot'. Compounds 2 and 3 proved to be not only excellent catalysts for the Suzuki and the Heck cross-coupling reactions, but they are also very convenient to use: The toluene solutions of the 'one-pot' syntheses can be used directly for the catalytic reactions, thereby saving the time-consuming isolation of the catalysts. The Suzuki cross-coupling reaction catalyzed by 2 and 3 can be performed in air at 100 °C in toluene of technical quality: in the presence of only 0.001 mol% of catalyst, several electronically deactivated and sterically hindered aryl bromides are quantitatively coupled with phenylboronic acid within a few minutes of reaction time. Furthermore, complex 2 enables the use of activated and non-activated aryl chlorides as coupling partners in the Suzuki reaction. Compounds 2 and 3 have also been shown to be highly active and reliable Heck catalysts: Very low catalyst loadings and short reaction times are required for the quantitative coupling of several electronically deactivated and sterically hindered aryl bromides with various olefins at 140 °C. At increased temperatures, even electronically deactivated and sterically hindered aryl chlorides can be efficiently coupled with olefins in the presence of only 0.01 mol% of catalyst. Schweizerische Chemische Gesellschaft.
Regioselectice Trans-Cis Photoisomerization of m-Styrylstilbenes
Ito, Yoshikatsu,Uozu, Yoshihiro,Dote, Toshimichi,Ueda, Masahiro,Matsuura, Teruo
, p. 189 - 198 (2007/10/02)
Trans-cis photoisomerization of m-styrylstilbenes, i.e., 2,4,6-triisopropyl-3'-styrylstilbene (TISS), 2,4,6-trimethyl-3'-styrylstilbene (TMSS), and 3-styrylstilbene (SS), and of stilbenes, i.e., 2,4,6-triisopropylstilbene (TIS), 2,4,6-trimethylstilbene (TMS), and stilbene (S), are studied under direct or benzophenon-sensitized irradiation in hexane.Measurements of quantum yields for isomerization have revealed that although the styrylstilbene molecule bears two styryl groups, the reaction is highly regioselective, depending upon the excitation conditions and reactant structures.For example, isomerizations of trans,trans-TISS and trans,cis-TISS occured either at the 2,4,6-trisubstituted styryl side upon direct excitation or at the unsubstituted styryl side upon sensitized excitation.When the starting material carries an unsubstituted cis-styryl group, the major isomerization always occurred at this moiety by either direct or sensitized axcitation, e.g., cis,trans-TISS ---> trans,trans-TISS, cis,cis-TISS ---> trans,cis-TISS, and cis,trans-SS ---> trans,trans-SS.Furthermore, the photoisomerization of cis-SS was found to be one-way.These results are interpreted in terms of the usual "energy sink" concept: the excited-state energies (ES and ET) of the stilbene chromophores depend on molecular distortion in a subtle manner.It seems that an extremely rapid cis ---> trans isomerization rate of the unsubstituted cis-styryl group is also responsible for the observed preferential photoisomerization of this group.Finally, the cis,cis isomers of TISS, TMSS, and SS underwent upon sensitized excitation minor but substantial one-photon two-double-bond isomerization (cis,cis ---> trans,trans) in addition to major one-double-bond isomerization.This reaction is not common, since the two isomerizing double bonds are cross-conjugated.
