Arylzinc chloride

A general method for the Pd-catalyzed cross-couplings of alkyl- and arylzinc chlorides with aryl, heteroaryl, and vinyl chlorides was reported by Dai and Fu.420 They determined that the commercially available and air stable complex Pd(PBut3)2 catalyzed these reactions leading to the formation of an sp2)C - sp2)C bond (Scheme 164). Remarkably, bulky biaryls with two, three, or even four 0/7/fo-substituents (e.g., 323) were obtained in very high yields (76-96%). 

Similarly, the benzannulated enyne-allenes 172 and 173 were prepared from the propargylic acetates 171 by cuprate addition or by Pd-catalyzed addition of arylzinc chloride (Scheme 20.35) [49]. The presence of a butyl group and a p-anisyl group at the allenic terminus of 173a and 173b permits competition between a formal ene reaction and a formal Diels-Alder reaction leading to 174 and 175, respectively. 

They tried Ni catalysts with chelating amine and phosphine ligands in the reaction of phenylzinc bromide with A-benzoyloxymorpholine 2a and observed that in the presence of NiCl2(PPh3)2, n-alkyl, aryl and functionalized arylzinc chlorides can be aminated with A,A-disubstituted O-benzoylhydroxylamines in good yields (Schemes 20 and 21). Attempted amination of secondary and tertiary alkylzinc chlorides failed to yield the expected product. 

Theuseof DMPU (l,3-dimethyl-3,4,5,6-tetrahydro-2(l//)-pyrimidmone) as acosolvent in THF has been reported to increase the amination yield of arylzinc chlorides with Erdik and Omiir also reported competitive kinetic studies for the amination of substituted phenylmagnesium bromides and CuCN-catalyzed phenylzinc chlorides with acetone 0-(mesitylenesulfonyl)oxime 6f in THF and analyzed the rate data via the Hammett... 

Grignard reagents and diazonium zinc chloride double salts have been used to prepare azo compounds. The reaction of arylzinc chloride with a diazonium salt has also been used. By this means, mixed aromatic-aliphatic azo compounds have been prepared. 

Asymmetric 1,4-addition of arylzinc chlorides to ( >3-arylpropenals has proceeded with high enantioselectivity in the presence of a rhodium-(/ )-binap catalyst and chlorotrimethylsilane.102 The corresponding 3,3-diarylpropanals were obtained in high yields and excellent enantiomeric excess (98-99% ee). 

Equally useful palladium-catalyzed coupling reactions between aryl halides and aryl organometallics have been developed, in which the latter component is usually either a trialkylstannane derivative or the corresponding arylzinc chloride species. In contrast to the foregoing nickel-mediated couplings with... 

In the presence of a Pd catalyst, CIPd[P(Cf,Hvinyl iodide couples with mctalatcd aromatics, particularly arylzinc chloride or arylboronic acids. Aryl Grignard reagents, however, couple in very low yield. The resulting C-aryl glucals can be converted to C-aryl glycosides by functionalization of the enol ether double bond.2... 

Biphenyls. The cross-coupling of arylzinc chloride reagents with aryl triflates constitutes a convenient method for assembling biphenyls. The zinc reagents are accessible from directed o-metallation and metal-metal exchange. 

Coupling of the sterically congested arylzinc chloride 21 with 1-cyclopentenyl chloride (22) gave 23 in high yield when Pd[P(t-Bu3)]2 was used as a catalyst in THF-NMP [51],... 

Daskapan, T. Preparation of primary aryl amines via arylzinc chlorides in good yields. Tetrahedron Lett. 2006,47, 2879-2881. 

The use of the well-defined PEPPSI-IPr precatalyst led to a significant improvement with respect to the rate and the substrate scope of the Negishi alkyl-alkyl coupling reactions (Scheme 3.62). This precatalyst can also be used to promote the cross-couphng of alkyl or aryl halides and sulfonates with arylzinc chloride reagents at room temperature by judicious choice of the solvent and additive (LiCl or LiBr) [236]. 

Similarly, S-acetyl-l-thlo-compounds with arylzinc chlorides and Pd(PPh ) give aryl C-glycosides, but with inversion of configuration. 50 approach to aryl C-glycosides by way of phenyl 1-thio-... 

Next, attention was directed towards the nucleophilic nature of the organozinc reagent potentially affecting the 1,2-migration. Various alkenyl phosphates and tosylates were coupled to arylzinc chlorides possessing different electronic and sterical properties. All reactions were conducted using the optimized catalytic... 

Arylacetic ethyl esters are prepared from arylzinc chlorides and ethyl bromoace-tate with a catalytic amount of Ni(acac)2 and a phosphine ligand at -5 °C [88],... 

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