Sonogashira-type

In 2003, Van der Fycken pubhshed a copper- and palladiirm-free microwave-assisted Sonogashira-type protocol in water with phenylacetylene as the alkyne (Scheme 51) [69]. The phase-transfer agent TBAB was used to facilitate... 

A microwave-assisted Cu-catalyzed Sonogashira-type protocol on aryl iodide substrates without the involvement of a palladium catalyst has also been published (Scheme 54) [71]. Reactions were executed using Cut and CS2CO3 in NMP at 195 °C. The application seems to be fairly limited since there are indications that only (hetero)arylacetylenes are suitable coupHng partners for this protocol. In addition, aryl bromides react more sluggishly than aryl iodides. Moreover, even on aryl iodides the reaction times required are on the order of hours. 

A potentially interesting development is the microwave-assisted transition-metal-free Sonogashira-type coupling reaction (Eq. 4.10). The reactions were performed in water without the use of copper(I) or a transition metal-phosphine complex. A variety of different aryl and hetero-aryl halides were reactive in water.25a The amount of palladium or copper present in the reaction system was determined to be less than 1 ppm by AAS-MS technique. However, in view of the recent reassessment of a similarly claimed transition-metal-free Suzuki-type coupling reaction, the possibility of a sub-ppm level of palladium contaminants found in commercially available sodium carbonate needs to be ruled out by a more sensitive analytical method.25 ... 

Scheme 6.37 (a) Transition metal-free, (b) copper(l)-catalyzed Sonogashira-type couplings. 

Wang also reported efficient Sonogashira-type reactions in DMF (Eq. 11.18) [32], Interestingly, the generally most efficient palladium catalysts did not have to be... 

Substituted propargylic carbonates react with terminal acetylenes in the presence of a catalytic amount of Pd(PPh3)4 and Cul to produce Sonogashira-type cross-coupling products (Eq. 9.114) [84]. Presumably, the reaction proceeds through an allenylpalladium complex. Addition of a salt, such as KBr, increased the yield of the coupling product. Only tetrasubstituted allenes could be obtained by this procedure. 

A Pd(II)- and Ni(II)-catalysed Sonogashira-type cross-coupling of vinyl tellurides and vinyl tellurium dichlorides with terminal alkynes... 

Leadbeater, N.E., Marco, M. and Tominack, B.J. (2003) First examples of transition-metal free Sonogashira-type couplings. Org. Lett., 5, 3919. 

Fig. 12.8 Synthetic semi-automated solid-phase strategy for the modification of DNA bases by chromophores via an acetylene bridge and Sonogashira-type cross-couplings.

The dendrimers 23a-c were used in a copper-free Sonogashira-type coupling reaction between phenylacetylene and iodobenzene or bromobenzene. The catalyst amount was 1 mol % per catalytic group (i.e., 1/4, 1/8 and 1/16 mol% depending on the dendrimer generation generations 1, 2 and 3), and the temperature range was 25-120 °C. 

TABLE 1.6. Silver-Catalyzed Sonogashira-Type Coupling... 

In 2006, Li and Wang reported the palladium-free, silver-catalyzed Sonogashira-type coupling of aryl halides and terminal alkynes. The reaction proceeds in high yield in the presence of catalytic silver iodide, triphenylphosphine, and potassium carbonate. Although the mechanism remains unclear, it is evident that the silver acetylide has a role, as the acetylide is formed on mixing of the reagents (Scheme 1.54).122... 

The versatility of silver-catalyzed desilylation has been further extended by its use in a one-pot catalytic desilylation/Sonogashira-type coupling reaction. In the total... 

As shown in Equation (37), 4,5-dibromo-2-furaldehyde and methyl 4,5-dibromo-2-furoate underwent regioselective cross-coupling reaction at the 5-position with alkynes under Sonogashira-type conditions, presumably due to the activation of the 5-position by the electron-withdrawing groups at the 2-position toward oxidative palladium insertion <1998TL1729, 1999EJO2045>. 

This review is divided into four main sections, covering the Heck, Stille, and Suzuki reactions, with miscellaneous reactions being included at the end. Processes featuring alkynes in copper co-catalyzed Sonogashira-type couplings have been included in the section on Heck reactions. This review does not cover carbon-carbon bond formation processes using immobilized catalysts. Similarly, fluorous-phase syntheses " and those on polyethylene glycol " are excluded. 

Lopez-Deber, M. P., Castedo, L., Granja, J. R. Synthesis of N-(3-Arylpropyl)amino Acid Derivatives by Sonogashira Types of Reaction in Aqueous Media. Org. Lett. 2001, 3, 2823-2826. 

Alkynyltrimethylsilanes act as effective alkynyl donors in the presence of a fluoride ion source [15]. Recent studies on the Sonogashira-type reaction of alkynylsilanes have revealed that the use of a Cu(I) [554] or Ag(I) [555] salt leads to highly efficient coupling with vinyl and aryl triflates (Scheme 10.213). 

In 2003, Sonogashira-type palladium-catalyzed coupling of thiol esters with... 

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