Study On Stille Cross-coupling Reactions Of Aryltiazene As Substrate

The C-C bonds were formed by coupling reaction with aryltriazene of electrophiles andorganic nucleophile in the presence of a Lewis acid. The formation of C-C bonds is crucial to theconstruction of the carbon skeleton of the organic compound, playing a very important role inorganic synthesis. Aryltriazene was synthesized by diazotization with primary aromatic amine asraw materials, which is marked by simple technique, easy operation as well as low cost. AlthoughAryltriazene is a kind of widely used reagents, and it was synthesized by diazotization withprimary aromatic amine as raw materials, which is marked by simple technique, easy operation aswell as low cost. Aryltriazene has been widely used in organic synthesis, such as protect group ofnatural product synthesis, combinatorial chemistry, pol ymer synthesis, new heterocyclic formation,the formation of complexes with aryltriazene as ligands and coupling reation etc., as well asfunctional group transformation, protection and luminescent materials etc, among them a fewstudies are applied to the coupling reaction. Related reports were published in literature in recentyears, which mainly involves Suzuki coupling reaction of palladium-catalyzed. Research reportedon Stille coupling reaction is less in the system involved with Lewis acid while aryltriazene assubstrate.Related reports were published in literature in recent years, which mainly involves Suzukicoupling reaction of palladium-catalyzed. Research reported on Stille coupling reaction is less inthe system involved with Lewis acid while aryltriazene as substrate. The use of Lewis acid asco-catalyst instead of strong base is beneficial to certain alkaline sensitive substrate. The use ofaryltriazene provides a kind of new coupling reaction substrate, which expanded its scope ofapplication. Therefore, it is very necessary that study on the coupling reaction of participation ofLewis acid with aryltriazene as substrate. In this paper, we carried out the study on Stille couplingreaction with aryltriazene as the substrate of Stille coupling r eaction, which main content includesas below:(1) Optimization of reaction conditions, including selection of solvent, screening ofLewis acid, controlling of temperature, the ratio of reaction substrate, choosing of catalyst,studying on substrate generality;(2) Aryltriazene, the electrophiles were synthesizedin the light ofthe method in the literature; As for arylstannanes nucleophile were acquired by purchase;（3）TheC-C bonds were formed by coupling reaction with aryltriazene as electrophiles and arylstannanesas nucleophile in the presence of catalysts. The reaction process was monitored by TLC. Theproducts were purified by column chromatography. The structure of these samples werecharacterized by1H NMR and13C NMR.The catalyst of Pd/C can be recycled easily due to itsinsoluble in the reaction system. Main research results as follows:(1) In homogeneous catalytic system, the optimal reaction conditions were obtained by optimizingfour factors of Stille coupling reaction: room temperature of30oC, the solvent, nitrogen protection, the reaction time of12h,4-(triphenylphosphine) palladium (0) as catalyst (1.25%), the molar ratio of substrate:p-nitrophenyl-trazene:3-butyl phenyltin=1:1.75. Under this conditions, universal test of9kinds of substrateshowed that the yield can reach91%with aryltriazene as substrate and the overall yield is better, and thesubsrate possessing universality. When electron-withdrawing group is on the benzene ring of aryltriazene,it is better for its generation of the coupling product. In contrast, the coupling yield declined with electrondonating groups. The ortho substituent steric affected its yield rate; reactivity and chemistry selective ofaryltriazene was better arylbromide and aryliodides.(2) In the two-phase catalytic system, the optimal reaction conditions were obtained by optimizingStille coupling reaction: the amount of5%Pd/C catalyst is7.5%times vs that of triazene,n(triazene):n(3-N-butyl phenyltin)=1:1.25,1,4dioxane as solvent, the reation time for12h, universaltest of9kinds of substrates showed that the highest yield can reach97%, and the overall yield is better. Soaryltriazene was used as substrate in the reation system. The experiments were carried out at roomtemperature under mild reaction condition. The catalyst of carbon supported palladium can be recycled,because it cannot dissolvent in the solvent. And can be used repeatedly which was almost unchanged. Itwas shown that this methode is suitable for triazene with electron withdrawing/donating groups, andshowed better universality at the same tome.The Stille coupling reaction can be implemented at room temperature due to the use ofaryltriazene. The reaction has less by-products and high yield and not need to be in the presence ofalkali. Less by-products of self-coupling and higher yield of cross-coupling reaction are due to thereation can be carried out at room temperature.