Transition-metal-catalyzed cross-coupling reaction

Transition-Metal-Catalyzed Cross-coupling Reactions 

---

Recent trend in the synthesis of olefinic pheromones is the use of transition metal-catalyzed cross coupling reaction for carbon-carbon bond formation. Scheme 8 summarizes a synthesis of the termite trail marker pheromone, (3Z,6Z)-3,6-dodecadien- l-ol (2) by Oehlschlager [19]. The key-step is the palladium-catalyzed cross-coupling of allylic chloride A and alkenylalane B. 

Isoxazoles are privileged aromatic heterocycles due to their wide spectrum of biological activities and their use as versatile building blocks in organic synthesis. Recent progress in the field of transition-metal-catalyzed cross-coupling reactions on isoxazole systems has been summarized and discussed <06EJO3283>. 

The transition metal cross-couplings of allenes described here offer practical solutions for the modification of 1,2-dienes and access to the preparation of highly functionalized 1,3-dienes, alkynes and alkenes, which are often not easily accessible in a regio- and stereoselective manner by classical methods. Some of the prepared alkynes or functionalized allenes serve as important intermediates in syntheses of natural products, biologically active compounds, e.g. enynes and enyne-allenes, and new materials. It can be predicted that further synthetic efforts will surely be focused on new applications of allenes in transition metal-catalyzed cross-coupling reactions. 

Transition-metal-catalyzed cross-coupling reactions also represent a powerful approach for the construction of carbon-carbon bonds. As a result, these processes have been widely studied in the past few decades. Among the transition metals... 

Due to the significant biological interest of quinoxalines, several methodologies for derivatization of these heterocyclic skeleta have been reported. The majority of the reactions involving quinoxalines are analogous to those of the other heterocycles discussed previously including SnAt substitution, lithiation, and transition metal catalyzed cross coupling reactions. 

Transition-metal-catalyzed cross-coupling reactions. 543... 

To make the transformation even more useful, different carbon electrophiles should be connected sequentially in a stepwise manner. For this purpose, a transition-metal-catalyzed cross-coupling reaction opened the way. As shown in Scheme 22, cinnamyl chloride is treated with bis(iodozincio)methane (3) in the presence of palladium catalyst with various phosphine ligands. Phosphine ligands, having an electron-withdrawing group, such as tris[3,5-bis(trifluoromethyl)phenyl]phosphine and tris(2-furanyl)phosphine, show excellent results47. 

Intramolecular nucleophilic reaction of sp2-geminated organodimetal species gives cycloalkyl metal derivative, which can be converted into the corresponding alkenyl iodide. The iodide can be used for further transition-metal-catalyzed cross-coupling reaction (equations 61 and 62)86. 

Like other organozinc reagents65, zincates are excellent nucleophiles in the transition metal catalyzed cross-coupling reaction. Tri- and tetra-arylzincates are reported to... 

Much work has been directed towards the synthesis of thiophene oligomers and polymers. This is due to the current interest in research on conducting polymers and molecular electronics (92CRV711). Two main approaches have been used for making such polymers (i) chemical (e.g. FeCl3) or electrochemical oxidation of monomeric thiophenes and (ii) transition metal-catalyzed cross-coupling reactions. 

For transition metal-catalyzed cross-coupling reactions of Grignard reagents, see the appropriate transition metnL... 

Transition metal-catalyzed cross-coupling reactions between vinyl organometallic compounds and unactivated alkyl halides that can be usually performed with palladium, nickel and cobalt are of particular synthetic interest [37-39]. Recently, the groups of Cahiez [48] and Cossy [49] concurrently reported the first iron-catalyzed reaction of alkenyl Grignard compounds with primary and secondary alkyl halides (X=Br, I) (Scheme 5.15). The two protocols basically differ in the iron source... 

Most transition metal-catalyzed cross-coupling reactions also yield small quantities of the product of homocoupling of the nucleophilic reactant[16, 114,115]. In particular terminal alkynes [116, 117] or metalated terminal alkynes [118] readily dimerize to the corresponding 1,3-butadiynes (Scheme8.14). 

For the synthesis of a cavitand functionalized with terpyridyl groups via rigid linkages, transition metal catalyzed cross-coupling reactions are especially well suited. Starting with the boronic acid ester 48 [65], attachment of the terpyridyl groups to the cavitand was realized by Suzuki-Miyaura reaction with the tetraiodo-cavitand 47 (Fig. 15). 

Transition metal-catalyzed cross-coupling reaction has become the most important method for the formation of aryl-aryl bonds. The reaction of aryl halides and sulfonates with organomagnesium compounds is usually referred... 

Enynes can also be synthesized in excellent yields with high regio- and stereoselectivity by transition metal catalyzed cross-coupling reaction. Thus, ( >l-alkenyl-disiamylboranes react with 1-halo-1-alkynes in the presence of catalytic amount of tetrakis(tripheny]phosphine)palladium to afford conjugated trans enynes (Eq. 100)145). 

Transition metal-catalyzed cross-coupling reactions of thiophenes have been extensively covered in CHEC-II(1996). These include ... 

---