Palladium-catalyzed cross-coupling with

Palladium-catalyzed cross-coupling with organoboron compounds... 

A distannation product of 2-butyne-l,4-diol oxidatively cyclizes to provide 3,4-bis(stannyl)furan, which then undergoes palladium-catalyzed cross-coupling with an aryl iodide to give 3,4-diarylfuran (Scheme 31).152,153... 

Palladium-catalyzed Cross-couplings with Organolead Compounds 889... 

Fluorosilylsubstituted aryl derivatives were found to be useful reagents for carbon-carbon bond formation via palladium-catalyzed cross-coupling with aryl halides in the presence of fluoride anions as Si—C bond activator in dimethylformamide (DMF), as well as rhodium-catalyzed 1,4-addition to a, 3-unsaturated ketones in the presence of a fluoride anion source (Equation 14.11) [66, 69, 70],... 

Although there have been few new developments in the period since 1993, halogenopyrazines 42 have been convenient precursors for a variety of pyrazine derivatives. For example, the halogenopyrazines 42 are cyanated by palladium-catalyzed cross-coupling with alkali cyanide or by treatment with copper cyanide in refluxing picoline, to yield cyanopyrazines 48. Alkoxypyrazines 49 are produced by treatment with alkoxide-alcohol, and aminopyrazines 50 are prepared by amination with ammonia or appropriate amines. The nucleophilic substitution of chloropyrazine with sodium alkoxide, phenoxide, alkyl- or arylthiolate is efficiently effected under focused microwave irradiation <2002T887>. 

Stannylquinones.1 The quinone synthesis based on addition of alkynyllithiums to substituted cyclobutenediones (13, 209-210, 284) can provide stannylquinones. Thus thermolysis of the alkynylcyclobutenol 1 with Bu3SnOCH3 results in rearrangement to the stannylquinone 2. As expected, these stannylquinones undergo palladium-catalyzed cross-coupling with organic halides (Stille reaction, 14, 35), particularly with allylic halides. 

Ort r-substituted cyclohexadienyl aryl iodide 465 undergoes palladium-catalyzed cross-couplings with C-, N- and O- nucleophiles affording tricyclic chromans 466 with good levels of diastereoselectivity (Equation 193, Table 23) <1998SL748, 1999JOC1875>. 

The (E)- and (Z)-regioisomers of 6-ethylidenedioxadisilacyclohexane 1134 undergo palladium catalyzed-cross coupling with methyl-2-iodobenzoate to furnish dihydroisocoumarins with excellent (E)- or (Z)- selectivity (Scheme 282) <20030L1119>. 

The stereospecific insertion of 2-monosubstituted alkenyl carbenoids was successfully employed in the preparation of 1-alkyl-1-zircono-dienes. The Z and E carbenoids of 1-chloro-l-lithio-l,3-butadiene (69 and 70, respectively) are generated in situ fromE- andZ-l,4-dichloro-2-butene [53] (Scheme 25). Inversion of configuration at the carbenoid carbon during the 1,2-metalate rearrangement stereospecifically yields terminal dienyl zirconocenes 71 and 72 [54] (Scheme 25). As the carbenoid-derived double bond is formed in 9 1=Z E for 69 and >20 1=E Z isomeric mixtures for 70, the metalated dienes 71 and 72 are expected to be formed with the same isomeric ratio. Carbon-carbon bond formation was achieved by palladium-catalyzed cross-coupling with allyl or vinyl halides to give the functionalized products with >95 5 stereopurity [55-57]. 

Palladium-Catalyzed Cross-Coupling with Organometallic Reagents... 

The procedure is very easy to reproduce and the palladium-catalysed crosscouplings may be applied to a wide range of substituted 4-tosylcoumarin and arylboronic acids. The method successfully broadens existing approaches for the cross-couplings of tosylate with boronic acids by using palladium as the catalyst. Table 4.1 demonstrates diverse tosylates that can undergo palladium-catalyzed cross-couplings with various arylboronic acids successfully. 

The coupling of stable organosulfur compounds with boronic acids is of great synthetic importance, since both reaction partners are readily available, low toxicity, and are stable toward many reagents. 4-Halo-n-butyl and normal thio esters (Fig. 2) were prepared and investigated as substrates for palladium-catalyzed cross-coupling with boronic acids. 

Chloro-2,3-diethyl-2-cyclobutenone (611) undergoes a palladium-catalyzed cross-coupling with 2-(tri- -butyl)stannyl-5-trimethylsilylthiophene (612) to give the intermediate compound (614) (Equation (110)). Without isolation, (614) is converted to the benzothiophene (613) on thermolysis at 100°C followed by acetylation. Although this procedure seems not to be generally applicable to benzo[6]thiophene synthesis, it provides a general synthesis of dibenzothiophenes, and thus a series... 

When the Uthium enolate intermediate 9 was trapped by addition of a solution of Af-phenyltriflimide in hexamethylphosphoramide (HMPA) or fVA/ -dimethylpropylene urea (DMPU), the reaction smoothly delivered the Z-vinyl triflate 11 in 74% yield (Scheme 3). With the pure Z-vinyl triflate in hand, we turned our attention to its palladium-catalyzed cross-coupling with tin species. Under optimized crmditions, Pd2(dba)3 and triphenylarsine in fV-methyl-2-pyrrohd(Mie (NMP) at 40 °C, the cross-coupled products were obtained in good yields with retention of the Z-stereochemistry of the starting Z-vinyl triflate. These optimized conditions appUed to tributyl(vinyl)stannane and the Z-vinyl triflate from 11 dehvered the Z-diene compoimd 12,... 

Terminal alkynes may be deprotonated with LDA and transmet-allated with zinc to undergo palladium-catalyzed cross-couplings with aryl electrophiles (Scheme O... 

III.2.12.1 Palladium-Catalyzed Cross-Coupling with Acyl Halides and Related Electrophiles... 

Scheme 1.26 Palladium-catalyzed cross-coupling with allyltin 65 (Kosugi, Migita, 1977)...

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