Pd -catalysed arylation

A tandem enolate-arylation-allylic cyclisation, in which an essential z-butyldimethylsilyl ether protecting group delays the cyclisation step until the Pd-catalysed arylation is complete, enables 1-vinyl-l//-[2]benzopyrans 54 to be prepared from 2-bromobenzaldehyde (Scheme 32) <00CC1675>. 4-Substituted isochromans 55 are formed from aldehydes by a Pd-catalysed termolecular queuing cascade. The sequence involves cyclisation of an aryl iodide onto a proximate alkyne followed by an allene insertion. Transmetallation with indium then allows addition to the aldehyde (Scheme 33) . 

Rhodium-catalysed asymmetric cyclization/hydroboration followed either by Pd-catalysed arylation or by oxidation was applied to the synthesis of a number of chiral, non-racemic carbocycles and heterocycles. Thus, reaction of enyne (28) with catecholborane, catalysed by a 1 1 mixture of [Rh(COD)2]+ Sbly,- and (S)-BINAP (5 mol%), followed by Pd-catalysed arylation with /7-IC6H4CF3, afforded benzyli-denecyclopentane (29) in 65% yield with 88% ee.46... 

The N-aryl imines 412 as protected anilines can be prepared by Pd-catalysed arylation of benzophenone imine with aryl halides using DPPF and BINAP as ligands, and aniline derivatives are obtained by deprotection [204a],... 

Compound 1 has been successfully employed in controlling the high enantioselectivity of Pd-catalysed arylation and alkenylation of olefines using aryl(alkenyl) triflates (e.g. equation 26)238,239. The yields and optical purity of the products are distinctively lower with aliphatic amines (Et3N, i-Pr2NEt), pyridines (2,6-dimethyl-, 2,6-di-f-butyl-4-methyl-) and inorganic salts (AcONa, Na2C03) as bases. 

More recently, Livinghouse and co-workers studied the effect of Cu(I) on Pd-catalysed arylation of secondary phosphine boranes. Apart from a marked beneficial effect on the coupling elSciency, they discovered that Cu(I) is able to suppress the base-mediated racemisation of the phosphide borane intermediate, to generate a configurationally stable metallophosphide 47 (Scheme 6.22). Consequently, tertiary phosphine boranes 48 were obtained with retention of configuration, in good yields and excellent enantioselectivities. 

Table 6.7 Substrate screening for Pd-catalysed arylation of 49 (Scheme 6.23).

Scheme 6.24 Proposed mechanism for Pd-catalysed arylation of secondary phosphines.

Table 6.9 Results of Pd-catalysed arylation of silylphosphines with o-iodoarenes (Scheme 6.28).

Scheme 6.29 Pd-catalysed arylation with 2-iodo-Af,Af-diisopropylbenzamide.

Scheme 8.31 Pd-catalysed arylation of enolates derived from 79.

The reaction of 130a with one equiv. of Hg(TFA)2 in CHCI3 gave smoothly monosubstituted product 131a in 70% overall yield (Scheme 3.28). The Pd-catalysed arylation (Pd(OAc)2/PPh3/NaI/Ar-I) was then used to form... 

The Pd-catalysed arylation of tertiary allylic alcohols with aryl halides (equation 4), in the presence of a base, produces aryl substituted allyl alcohols in varying yields, and a mechanistic scheme has been proposed. 

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