Sonogashira coupling of alkynes

General Procedure for Sonogashira Coupling of Alkynes and Aryl Chlorides According to Plenio and Kollhofer[47]... 

Sonogashira coupling of alkyne 50 with aryl iodide 51 affords the diaryl alkyne 52 oxidation of which produces the 1,2-diketone 53. Hydrolysis of the acetal moiety prior to a proline-induced aldol cyclisation generates a chromanone from which the [ljbenzopyrano-[2,3-c][l]benzopyranone rotenoid system is obtained <07T11878>. 

Sonogashira coupling of alkynes with 3-iodoflavones leads to 3-alkynylflavones and is best effected using (5)-prolinol it is successful in aqueous conditions <03T9563>. The ylide phenyliodonium )w(phenylsulfonyl)methylide inserts into the 2,3-double bond of flavones and offers a direct route to 3-substituted flavones <03T7929>. 

The Sonogashira coupling of alkynes with aryl halides has undergone amazing developments during the past three decades, with the numbers of potential... 

As we have commented earlier, there are some reports in where polymers are used to act as interface between the metal NPs and the G support increasing the adherence of the metal NPs to Gs. In one of these examples polypropylene imine dendrimer has been used to increase the stability of Pd-Co alloy NPs on r-GO (Scheme 3.42). This dendrimer modified r-GO catalyst is able to promote the Sonogashira coupling of alkynes and aryl halides using K COj at 25 °C. Importantly metal leaching was not observed and as a reflection of the catalyst stability, the material could be reused six times with the catalytic activity decreasing only from 99 to 93 % after the sixth cycles. 

Two studies were carried out on the Pd-catalyzed Sonogashira coupling of alkynes with arylhalides (1) one-step preparation of an F-labeled alkyne for conjugation of iodoaryl-modified peptides (Poethko, personal communication) and (2) one-step preparation of4-[ F]iodobenzene for coupling with alkyne-modified compounds (Wiist and Kniefi 2003). 

The first Sonogashira coupling of alkynes with imactivated secondary alkyl bromides was reported in 2006 by Glorius and coworkers, using bioxazoline-derived NHC (IBiox) as ligands in (NHC) Pd dimer complexes 22 (Figure 4.6) [34]. 

More recently, a study with di- and mono-carbene Pd(II) complexes has demonstrated that the Sonogashira coupling of activated and non-activated aryl iodides can be carried out in an aqueous, aerobic medium and in the absence of amines. These results suggest that the moisture-sensitive copper-acetylide may not be present in this particular transformation, and that a Pd-acetyhde could be formed by deprotonation of the coordinated alkyne instead of transmetallation [130]. 

The second example involves the synthesis of ortho-dipropynylated arenes (Scheme 4.12b), which serve as precursors to tribenzocyclyne by way of an alkyne metathesis reaction (see also Scheme 6.31). Here, a Sonogashira reaction was carried out in a pre-pressurized (propyne at ca. 2.5 bar) sealed microwave vessel in a standard single-mode microwave reactor. Double-Sonogashira coupling of the dibromodiiodo-benzene was completed within 20 min at 110 °C [30]. 

Recent developments in palladium-catalyzed coupling reactions have arisen in the pyrimidine field as well. The Sonogashira coupling of bromopyrimidine 85 with alkynes 86 produced pyrimidines 87, important intermediates reported by Hart and co-workers in their approach to the cylindrospermopsin substructure . 

Dolphin has employed the Sonogashira coupling of terminal alkynes with zinc(II)-10-iodo-5,15-diphenylporphyrin (126) to prepare a series of alkynyl derivatives 127 [87], and similar syntheses of p-alkynyl porphyrins have been described [88]. 

Intramolecular Lewis acid-promoted reaction of coordinated propargylic ether with the silyl enol ether in 158 has been applied successfully to the construction of the highly strained 10-membered cyclic enediyne system 159, present in esperamycin and calicheamycin [39,40]. The enediyne system 157 was prepared by the Pd-catalysed Sonogashira coupling of (Z)-l,2-dichloroethylene (154) with two different terminal alkynes 155 and 156. 

The concept of alkyne activation by Sonogashira coupling was successfully extended to the in situ generation of alkynones that are highly reactive and versatile synthetic equivalents of 1,3-dicarbonyl compounds. Interestingly, ynones can be readily synthesized in a catalytic fashion by Sonogashira coupling of an acyl chlor-... 

Pyran-2-ones are valuable synthetic reagents and manipulation of the basic molecule enhances their value. The Sonogashira coupling of terminal alkynes with 4,6-dichloropyran-2-... 

Scheme 2 Alkyne activation by Sonogashira coupling of an electron-poor halide as an entry to coupling-Michael addition sequences...

Sonogashira Coupling of Highly Electron-Deficient Heterocycles to Activated Alkynes and Subsequent Amine Addition... 

A carbonyl group in conjugation with the triple bond exerts a strong polarization of the alkyne. Thus, Sonogashira coupling of acid chlorides 7 and terminal alkynes... 

Scheme 27 Mechanistic rationale of the decarbonylatlve Sonogashira coupling of indole-3-glyoxylyl chlorides 38 and terminal alkynes 2...

Ahmed MSM, Mori A (2003) Carbonylative sonogashira coupling of terminal alkynes with aqueous ammonia. Org Lett 5 3057-3060... 

Sonogashira coupling of terminal alkynes with aryl or vinyl halides requires a palladium(O) species as catalyst, a copper(I) cocatalyst and an amine as base. 

Ahmed, M. S. M., Mori, A. Carbonylative Sonogashira Coupling of Terminal Alkynes with Aqueous Ammonia. Org. Lett. 2003, 5, 3057-... 

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