Aryl iodides arylation

Preparation of aryl iodides Aryl diazonium salts react with sodium or potassium iodide to form aryl iodides This is the most general method for the synthesis of aryl iodides... 

Aryl iodides. Aryl iodides can be prepared by reaction of arenes with I2 and a mixture of A1C13 and CuCI 2. Yields are moderate to good, but the reaction fails with ethyl benzoate, acetophenone, and o-nitroanisole. The reagents are used in the ratio I2 A1C13 CuCl2 = 0.5 1 1. 

This form of active zinc prepared in the presence of an electron carrier can readily form arylzinc iodides at room temperature from aryl iodides. Aryl bromides reacted far more efficiently with reduced reaction times at refluxing temperatures. The newer two-pot lithium reduction procedures for the preparation of active zinc requires 3-4 h for a total preparation time. Whilst the old one-pot preparation of active zinc from the reduction of zinc salts with lithium... 

Aryl chloride Aryl iodide Aryl selenic acid Aryl sulfonic acid Azide... 

The Ullmann reaction (Figure 13.4) represents another synthesis of substituted biphenyls. In this process an aryl iodide or—as in the present case—an aryl iodide/aryl chloride mixture is heated with Cu powder. It is presumed that under standard conditions the aryl iodide reacts in situ with Cu to form the aryl copper compound. Usually, the latter couples with the remaining aryl iodide and a symmetric biphenyl is formed. In a few instances it is also possible to generate asymmetric biaryls via a crossed Ullmann reaction. In these cases one employs a mixture of an aryl iodide and another aryl halide (not an iodide ) the other aryl halide must exhibit a higher propensity than the aryl iodide to couple to the arylcopper intermediate. It is presumed that the mechanism of the Ullmann reaction parallels the mechanism of the Cadiot-Chodkiewicz coupling, which we will discuss in Section 13.4. 

Aryl iodides. Aryl iodides can be prepared in fair to good yields from aromatic hydrocarbons by the action of iodine and a copper salt. The observed reactivity order of various copper salts is CuClj > CuFj > CuCl > CufOOCCHjlj. The reaction is considered to involve a two-step sequence ... 

The Pd-catalyzed cross-coupling reaction of organoindium compounds was first reported in 1999.[4 ] The reaction was applied to triaryl-, trialkenyl- and trialkynylindiums, which coupled with aryl iodides, aryl triflates, or alkenyl triflates in high yields (Scheme 41) It is noteworthy that all of the organic groups on indium can participate in the coupling reaction. 

The order of reactivity of the aryl electrophiles in Pd-catalyzed cyanation is as follows aryl iodides > aryl triflates > aryl bromides > aryl chlorides. The lower the reactivity of the... 

The Inamoto group [44] has reported that the NHC-based pincer complex 30 is an effective catalyst for the cross-coupHng of aryl haUdes and butyl acrylate (Eq. (5.33)). This catalytic system is appHcable to aryl iodides, aryl bromides, and activated aryl chlorides, and compatible with functional groups including nitrile, ketone, and aldehyde. Notably, the reaction of 4-bromobenzonitrile can be retarded by a drop of mercury, suggesting that the catalytic system may be heterogeneous. 

Catellani and coworkers [31] observed dramatic effects of added olefins on the product selectivity in Pd-catalyzed/norbornene-mediated reactions of aryl iodides, aryl bromides, and aryl boronic acids in the synthesis of o-teraryls 91 (Scheme 3.23). 

Previously, Buchmeiser and coworkers developed catalysts which were based on bis-pyrimidine building blocks [77] and proved to be competent in cross<oupling reactions involving aryl iodides, aryl bromides and, with some limitations, also... 

Scheme 8.48 A three-component cascade coupling of an aryl iodide, aryl bromide, and acrylate involving norbornene as an essential additive [351],...

Pd"" -Catalyzed Direct Arylations Synthetic Scope Aryl iodides, aryl stannanes, and aryl iodonium reagents have all been successfully employed for the direct conversion of -Ar-H -Ar Ar Pd catulytic cyclcs. For example, the Pd-catalyzed reaction of naphthalene with PhSnClj in the presence of CuCl affords the phenylated product in modest yield as a mixture of the a/p isomers (Scheme 24.9) [13]. This transformation can be applied toward the phenylation of other electron-neutral arenes, albeit, with poor efficiencies. Interestingly, reactions of naphthalene and xylenes yield products via preferential arylation of the more steri-cally hindered C—H bond. Preliminary mechanistic studies suggest a Pd" catalytic cycle for these reactions. 

As an alternative to the aryl iodides, aryl bromides also undergo this reaction, although they generate the desired product in lower yields. A prerequisite for this transformation is that the symmetric arenes be applied in order to attain chemose-lectivity. Mechanistically, the reaction presumably proceeds via an iron-catalyzed radical process. Steric bulk does not appear to impact the product formation, thereby making it a reliable arylation methodology. A base is required in order to quench... 

Wu, X., Ekegren, J.K. and Larhed, M. (2006) Microwave-promoted aminocarbonylation of aryl iodides, aryl bromides and aryl chlorides in water. Organometallics, 25, 1434-1439. 

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