Tandem coupling

Scheme 20 Mechanism for iron-catalyzed tandem coupling/hydroarylation of aldehyde, aromatic alkyne, and anilines...

In an analogous manner, nitroalkenes can be utilized as the electrophile in a tandem coupling-cyclization process (Eq. 2.18). Addition of a stabilized sulfonium ylide such as 209, to a variety of nitroalkenes provides an intermediate nitronic acid, which upon displacement of dimethyl sulfide provides a mixture of the corresponding nitrocyclopropane (XL) and cyclic nitronate (XLI). The ratio of products is highly dependent on the structure of the nitroalkene. For example, without a substituent on the a-position of the nitroalkene (R = H), only the... 

The intramolecular coupling of an aldehyde and alkene at —78 °C, promoted by Sml2, in the presence of a ketone, has led to a tandem coupling-addition process. This reaction has proved to be synthetically very useful for the preparation of poly-oxygenated compounds (equation 139)523. This reductive coupling process may also be promoted in dry methanol,... 

Fig. 16.22. Palladium-catalyzed C,C coupling with bro-moiodobenzene regioselective tandem coupling I.

Fig. 16.24. Suzuki coupling for the synthesis of aromatic compounds with a functionalized side chain and regioselec-tive tandem coupling II.

Fig. 13.20. Suzuki coupling II for the synthesis of functionalized aromatic compounds regioselective tandem coupling II.

Liu HL, Jiang HF, Zhang M, Yao WJ, Zhu QH, Tang Z (2008) One-pot three-component synthesis of pyrazoles through a tandem coupling-cyclocondensation sequence. Tetrahedron Lett 49 3805-3809... 

Overman and co-workers [75] prepared alkenyltins via a vinyl triflate/ditin coupling. Mitchell and Kwetkat developed a simple route to acyltrimethylstannanes [187], whereas Hitchcock et al. [ 188] carried out a three-component tandem coupling reaction by reacting a 2-pyridyl triflate, aryl or heteroaryl bromides, and hexamethylditin with Pd(PPh3)4 the presence of LiCl to give azabiai yls (Scheme 4-48). 

The sulfur function in vinyl sulfides can be displaced in the same manner, using Ni or Pd catalysts, and the methodology has been extended to tandem couplings using l-bromo-2-phenylthioethene (Scheme 17). The regioselectivity of the first step is exactly as that observed with the corresponding p-bromo-vinyl ether (Scheme lb). In just the same way the 1,1-disubstituted alkene (79) can be converted into... 

The bis(chlorobipyridine) 192 readily underwent tandem coupling reactions to afford the... 

Tandem coupling and cycliasth a-arylvinylated cyclopropanes and het and oxazolidinones. Furan derivatises i... 

Tandem coupling and cyclization. Functionalized allenes are converted to a-arylvinylated cyclopropanes and heterocycles including epoxides, tetrahydrofurans, and oxazolidinones. Furan derivatives are formed from allenyl ketones." ... 

Tandem coupling cyclization Pd/CNT High catalytic activity. 359... 

A procedure for palladium-catalyzed tandem coupling-cyclization has been developed using trialkylsilylalkynes and o-iodoaniline <93TL647l >. The reaction is carried out as a single-step process using Pd(OAc)2 as a catalyst (Equation (13)). 

Fayol A, Fang Y-Q et al (2006) Synthesis of 2-vinylic indoles and derivatives via a Pd-catalyzed tandem coupling reaction. Org Lett 8 4203-4206... 

SCHEME 13 Representative example of how we con leted our four p-lipsugar-free eastern building blocks ). One sees qiecifically the synthesis of what would turn out to equal natural p-lipomycin. 

SCHEME 14 Accomplishing the synthesis of our only a-lipomycin candidate by a tandem coupling involving distannane 18 and the iodoalkene glycoside 32 ( sugar-containing eastern building block ). Juxtaposition of the specific rotation of our synthetic material and of natural a-lipomycin as reported by Zeeck et al. an excellent match once moie ... 

An interesting approach to l-en-5-ynes is the palladium-catalyzed tandem coupling of a cis-alkenyl iodide, a cyclic alkene, and a terminal alkyne (eq 27). With norbomene as the alkene, the coupling occurs in a stereodefined manner, and the enyne products are obtained in good yields. potassium cyanide can be used instead of an alkyne to yield the corresponding cyanoalkene. ... 

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