Nucleophile aryl-Grignard

Readily available nucleophilic aryl Grignard compounds can be coupled with aryl halide electrophiles to give unsymmetrical biaryls in the presence of Ni, Co, V, Ti, Cu, Cr, Fe, Pd and T1 salts [34] (Scheme 41). 

Example Sometimes copper solves other regioselecL-ivity problems. Addition of aryl Grignard (28) to enone (29) gives the anomalous product (30) in which the electrophile (29) has been attacked at the right atom but the nucleophile (23, arrows) has attacked with the wrong atom. 

When the phenyl-substituted alkynyl sulfone 42 is used as a substrate for the Cu-catalyzed carbomagnesiation, interesting nucleophile-dependent stereoselectivity is observed. While the use of allyl Grignard reagent results in a syn addition, the use of aryl Grignard reagent results in an awh -carbomagnesiation (Scheme 25). ... 

Other carbon nucleophiles may also be employed in such a coupling reaction that provides (3-amino ketones and polyol intermediates. As shown in Scheme 32, aryl-Grignard reagents react at low temperature with the Ai-Boc p-lactam 96 to afford p-aminoketones 97 in 90-96% yields as the exclusive products. In no case over-addition is observed, even when an excess of the Grignard reagent is present in the reaction medium. On the other hand, when the reaction is performed at room temperature, only tertiary carbinols 98 are produced. 

Aryl-A3-iodanes bearing an electron-deficient alkyl ligand such as aryl(sul-fonylmethyl)-A3-iodanes (Section 3.2.7) and aryl(perfluoroalkyl)-A3-iodanes are relatively stable. A series of (perfluoroalkyl)phenyl-A3-iodanes 96 were synthesized in good yields by treating bis(trifluoroacetoxy)-A3-iodanes with benzene in the presence of triflic acid [47]. The AModanes 96 transfer the perfluoroalkyl groups to a variety of nucleophiles with reductive elimination of iodobenzene. The nucleophiles involve Grignard reagents, alkyllithiums, enolate anions, alkenes, alkynes, trimethylsilyl enol ethers, arenes, phenols, and thiols. In these reactions, the AModane 96 serves as a source of the perfluoroalkyl cation and, in... 

In a limited number of cases, arylsilanes react with aldehydes as if they were aryl Grignard or aryllithium reagents. Both trimethyl(perchlorophenyl)silane and trimethyl(perfluoro-phenyl)silane react with benzaldehyde to give the corresponding 7.-(pcrhalophenyl)bcnzyl tri-methylsilyl ethers.163 Benzaldehyde reacts completely with trimethyl(perfluorophenyl)silane in diethyl ether in the presence of either a catalytic amount of the potassium cyanide/18-crown-6 complex in less than 5 hours at room temperature or potassium fluoride in dimethylform-umide.164 In the case of aryltrimcthylsilanes containing electron-withdrawing substituents in the ortho position, the reaction is observed only under the conditions of nucleophilic catalysis by potassium fluoride or cesium fluoride. 

Introduction. Ti-TADDOLates are a,a,a, a -tetraaryl-2,2-disubstituted l,3-dioxolane-4,5-dimethanolatotitanium derivatives. The most common substituents are R, R = Me/Me and Ph/Me, Ar=Ph and 2-naphthyl, X, Y = C1/C1, t-PrO/Cl, Cp/Cl, and i-PrO/i-PtO. The corresponding TADDOLs (2) are available in both enantiomeric forms from tartrate esters which are acetalized (R R CO) and allowed to react with aryl Grignard reagents. The reactions performed in the presence of Ti-TADDOLates or with Ti-TADDOLate derivatives include nucleophilic additions to aldehydes - - and nitroalkenes of alkyl, aryl, and allylic - groups aldol additions hydrophosphonylations and cyanohydrin reactions of aldehydes inter- and intramolecular Diels-Alder additions ... 

The reaction proceeds by (1) organometallic exchange, followed by (2) aryne formation, and (3) a regiospecific nucleophilic addition of the aryl Grignard to the aryne. These steps can occur or recur in tandem fashion to form from one to six new carbon-carbon bonds in a single operation [33,34]. Subsequently, the method was extended to alkenyl and alkynyl Grignards [35 Eq. (13)] and trimethylsilylvinyl Grignards [36]. 

In general, however, better yields are obtained with aryl Grignard reagents 33.46-12,-127 Some examples of the formation of disubstituted 1,3,5-triazines 34 using such carbon nucleophiles are... 

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