Cuprous iodide catalyst

A rapid MW-assisted palladium-catalyzed coupling of heteroaryl and aryl boronic acids with iodo- and bromo-substituted benzoic acids, anchored on TentaGel has been achieved [174]. An environmentally friendly Suzuki cross-coupling reaction has been developed that uses polyethylene glycol (PEG) as the reaction medium and palladium chloride as a catalyst [175]. A solventless Suzuki coupling has also been reported on palladium-doped alumina in the presence of potassium fluoride as a base [176], This approach has been extended to Sonogashira coupling reaction wherein terminal alkynes couple readily with aryl or alkenyl iodides on palladium-doped alumina in the presence of triphenylphosphine and cuprous iodide (Scheme 6.52) [177]. 

Halogen atoms. The introduction of side-chains on 9-trifluoromethyl-paullone 409 can be accomplished applying a Stille coupling (Scheme 86, Section 5.2.1.1 (2005EJM655)). Similarly, a Heck reaction of iodo 409 with terminal alkenes under standard conditions affords 2-substituted paullones 413 exclusively as E-isomers. The reaction of terminal alkynes with 409 in the presence of cuprous iodide and a palladium catalyst in triethylamine furnishes the 2-alkynyl-paullones 412 (2000BMCL567). 

The above-mentioned study was followed by a report of the groups of Ji, Loh and coworkers, who reported the application of a catalyst based on cuprous iodide and Tol-BINAP for the same purpose . Noteworthy is that the effective use of a C2-symmetric ligand in this reaction marks the end of the aforementioned metal-differentiating coordination concept. It was shown that a variety of Grignard reagents could be used for the... 

The displacement of a nuclear halogeno substituent by a cyano group can be done fairly readily in the pyrazine series, usually by treatment with cuprous cyanide, potassium cyanide plus cuprous iodide, or potassium cyanide in the presence of a palladium catalyst. The following examples illustrate these procedures ... 

The catalyst system for the coupling reaction was a Pd(II)-tri-phenylphosphine complex, usually prepared in situ, with excess triphenyl-phospUne and either cuprous iodide or cupric acetate as a co-catalyst. Alternatively, a preformed catalyst mixture prepared from these reagents may be utilized (see Experimental Section). When 2-methyl-3-butyn-2-ol was used as the protected acetylene, the intermediates 5a-d were converted to the corresponding aryl acetylenes 6a-d by a retro-Favorskii-Babayan (8) reaction utilizing potassium r-butoxide in toluene under conditions of slow distillation. In the case of p-iododimethylaniline (3e), trimethylsilylacetylene was used as the ethynyl source. The intermediate (5e) was treated with hydroxide to generate the free aryl acetylene 6e. The syntheses of 6d and 6e are described in the Experimental section below. 

As described above (Section 5.2), the Stephens-Castro reaction of alkynylcopper with aryl and vinyl halides in boiling pyridine is a useful route to aryl and vinyl acetylenes. Direct cross-coupling of organic halides, such as sp halides, with terminal alkynes is a more convenient procedure. Such a reaction is not so easy, but it can be done using a Pd-complex catalyst [41]. Especially facile Pd-catalyzed cross-coupling of aryl and alkenyl halides with terminal alkynes proceeds smoothly under mild conditions in the presence of a cocatalyst of cuprous iodide in amine solvents [Eq. (28)] [42]. This methodology is now used widely for the constiuction of conjugated arylalkyne or enyne systems [43], as described below. It is attractive from a synthetic point of view because mild reaction conditions and simplicity of the procedure are associated with recent developments in modem acetylene chemistry [44]. 

Example 3 was also repeated using from 5 to 10 mole % of cuprous oxide, cuprous chloride, cuprous iodide and copper dust, as the catalyst for conversion of the iodovanillin to hydroxyvanillin. Recovery of 5-hydroxyvanillin was 80-85% (remainder vanillin) with copper dust, from 70-80% with the copper oxide or salts. 

Doering et al." extended this application to the synthesis of tricyclic ketones from monocyclic diazoketones, using as catalyst copper powder, cupric sulfate, or cuprous iodide with apparently equal success. A sketchy advance report,12 claims the synthesis of 8,9-dehydroadamantane-2-one (5, m.p. 206.5-207.5°) via the acid chlorides (3) and (4) and the derived diazoketones. 

A typical Sonogashira reaction involves heating an aryl halide, catalyst and a terminal alkyne with cuprous iodide and triethylamine. This reaction does not require the preparation of an organometallic reagent, because transmetaUation occurs via an alkynylcopper, formed in situ. The main use of the Sonogashira reaction in heterocyclic chemistry is probably for the synthesis of intermediates for ring synthesis. ... 

Furthermore, Bumagin and Beletskaya reported the first coupling in neat water in the presence of a small amount tributylamine (10 mol%) and potassium carbonate as base [23], Surprisingly, the catalyst system consists of water-insoluble tri-phenylphosphine with PdCl2 and Cul at room temperature, resulting in high yields with aryl iodides and phenylacetylene. The role of cuprous iodide was noted to be important to facilitate the reaction, which may be rationalized by two connected catalytic cycles (Scheme 2). 

Copper (I) iodide Copper iodide (Cul) Copper monoiodide Copper(1 ) iodide Copper(l) iodide Cuprous iodide EINECS 231-674-6 EPA Pesticide Chemical Code 108301 HSDB 271 Hydro-Giene Natural marshite. Used as a feed additive, in table salt as source of dietary iodine, catalyst, in cloud seeding. Solid mpa 588-606° bp= 1290° d = 5.63 insoluble in all solvents. Atomergic Chemetals Blythe, Williams Ltd. Cerac Greet R.W. Co. Mitsui Toatsu Nihon Kagaku Sangyo Sigma-Aldrich Fine Chem. 

Phloroglucinol This phenol (3) can be prepared from 1,3,5-tribromo-benzene by treatment with sodium methoxide in methanol and DMF in the presence of cuprous iodide as catalyst. The resulting ether (2) is hydrolyzed to phloroglucinol (3) by concentrated hydrochloric acid. The overall yield is 85-95%. 

Dienes. Japanese chemists have prepared 1,5-dienes by reductive coupling of allylic haUdes with these complexes. For example, reaction of cyclohexylidenethyl bromide with the complex of lithium pyrrolidide and cuprous iodide in ether at 0° for 4 hr. gives the three products shown in equation I in essentially quantitative yield. The reaction is very sensitive, however, to the solvent and the temperature and also to the dialkylamine used for preparation of the catalyst. 

It is known that both copper acetate and cuprous iodide are effective catalysts for this reaction, as well as pure copper metal in the presence of oxygen. In addition, the salts... 

A highly efEcient amidation reaction of furans with iV-fluorobenzene-sulfonimide (NFSI) was developed, presumably proceeding via C-H bond activation. Cuprous iodide was employed as the catalyst, and various a-amidated furan derivatives were generated in good-to-excellent yields. This chemistry enables an economic method of synthesis of valuable ami-dated furans through a direct C-N bond-coupling process (140E5648). 

In this experiment, we will conduct some modern organic chemistry using a palladium catalyst. It is a rare opportunity for students in undergraduate laboratories to experience this powerful chemistry. We will react the lodosubstituted aromatic compounds, shown below, with 1-pentyne, 1-hexyne, or 1-heptyne in the presence of the catalysts, palladium acetate and cuprous iodide, to yield 4-substituted-l-pentynyl, 4-substituted-l-hexynyl, or 4-substituted-l-heptynylaromatic compounds. This reaction is called the Sonogashira coupling reaction. The reaction will be carried out in refluxing 95% ethanol as the solvent. In addition, piperazine will be employed both as a base and as a hydride donor. 

The bromo end-capped oligomers were converted to the acetylene terminated systems by the reaction with 2-methyl-3 butyn-2-ol, utilizing the catalyst system composed of triphenylphosphine, bis-tri-phenylphosphine palladium chloride, and cuprous iodide. Conversion of the generated butyn-adducts to the acetylene functionality was carried out by the hydrolytic displacement of acetone with potassium hydroxide in toluene. The displacement of acetone under basic conditions is an equilibrium reaction therefore, the acetone must be removed by codistillation with toluene. 

Two isomeric acetylenic benzothiazole monomers, 2-(3-ethynyl-phenyl)-5-ethynylbenzothiazole (3) and 2-(3-ethynylphenyl)-6-ethynyl-benzothiazole (4) were prepared according to the general reaction scheme shown below. The synthesis of the benzothiazole heterocyclic structure was carried out by the condensation of m-bromobenzoic acid with isomeric bromo-substituted o-aminomercaptobenzenes in poly-phosphoric acid (PPA). The bis-bromobenzothiazoles were converted to the acetylene systems by the reaction with 2-methyl-3-but3m-2-ol and subsequent displacement of acetone with base. The bromo displacement reaction utilized a catalyst composed of triphenylphosphine, (bis-triphenylphosphine)palladium dichloride and cuprous iodide. 

Zanina et al. have reported a method for the synthesis of a, acetylenic ketones from terminal alkynes and acid chlorides using cuprous iodide as a catalyst. The use of high temperature and toluene as the solvent in this protocol prompted Kundu and co-workers to develop a new procedure with triethylamine as the solvent and the base, which obviated many of the difficulties and enabled the reactions to be carried out at room temperature (eq 30). Zhang and co-workers have modified the conditions in order to couple monooxalyl chloride with terminal alkynes THE was used as the solvent with 2 equiv of triethylamine and 5 mol % of Cul. It is noteworthy that CuCl, CuBr, and Cul showed similar reactivity, while CuOTf was totally inert. 

SCHEME 1.1 Synthesis of alkyl aryl ethers using the cuprous iodide/phen catalyst system [5]. 

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