Regioselective arylations

The regioselective arylation of butyl vinyl ether was carried out by the same group, using Pd(OAc)2 as catalyst precursor and l,3-bis(diphenylphosphino)-propane (dppp) as the ligand, dissolved in [BMIM][Bp4] (Scheme 5.2-17) [90]. 

Scheme 5.2-17 Pd-catalyzed, regioselective arylation of butyl vinyl ether in a [BMIM][BF4] ionic...

The regioselective arylation occurs when the reaction of 2-arylpyridines with aryl halides is conducted with the aid of the ruthenium(ii)-phosphine complex as catalyst (Equation (66)).81 The ortho-position to the 2-pyridyl group is arylated predominantly. The aromatic imines are also arylated with the same catalytic system.82... 

Xu, L.J., Chen, W.P., Ross, J. and Xiao, J.L., Palladium-catalysed regioselective arylation of an electron-rich... 

M. Regioselective arylation of benzanilides with aryl triflates of bromides under Pd catalysis. Tetrahedron Lett. 2000, 43, 2655-2658. 

Terao, Y. Satoh, T. Miura, M. Nomura, M. Regioselective arylation on the y-position of a,/ -unsaturated carbonyl compounds with aryl bromides by Pd catalysis. Tetrahedron Lett. 1998, 39, 6203-6206. 

Asymmetric synthesis of tetraphenylenes 58-60 consists of two key steps, as illustrated by the synthesis of tetraphenylene 58 (1) regioselective arylation at... 

Such an arylation reactioncanneverthelessberendered regioselectiveifcoordinating atoms are present in the starting molecule at the appropriate position, directing the C-H activation at this position. Thus, 2-arylbenzoxazoles have been regioselectively arylated in the presence of palladium acetate and silver acetate (Scheme 10.54).86... 

Skerjl reported that ferf-butylcarbazate could be regioselectively arylated with the DPPF/Pd-catalyst [123]. When aryl bromides possessing orthosubstituents were used, reaction at the less hindered nitrogen was observed, Eq. (151). However, in the absence of ortho substitution, the arylation proceeded on the Boc-protected nitrogen. 

For the alkylation and alkenylation of C-H bonds, olefins and acetylenes are used as reactants. This type of coupling protocol is not applicable to arylation. Recently, a nitrogen-directed arylation of aromatic C-H bonds, leading to biaryl compounds has been developed. In 2001, Oi demonstrated that ruthenium(II)-phosphine can be used as a catalyst in the regioselective arylation of 2-arylpyridines using aryl halides (Eq. 9.34) [4 ]. The predominant ortho selectivity indicates that the coordination of... 

Diatylidene-9,10-dihydroanthracenes are available as ( /Z) mixtures from self cross-coupling of ( )-o-bromostilbenes. Of interest is the regioselective arylation of 2-hydroxybiaryls at the 2 -position. ... 

The palladium-catalyzed regioselective arylation of imidazo[l,2-fe][l,2,4]triazine 63 afforded 2, 6-difluoro-5 -[3-(l-hydroxy-l-methylethyl)-imidazo[l,2-Z)][l,2,4]triazin-7-yl]biphenylcarbonitrile 65 <05JOC5938>. 

An extension of this methodology to the functionalization of C(sp3)-H bonds in saturated /V-heterocycles was reported subsequently [69], Thereby, pyrrolidines and piperidines were regioselectively arylated with substituted boronates in the ct-position to the heteroatom (Scheme 16) [30],... 

Kakiuchi F, Matsuura Y, Kan S, Chatani N (2005) A RuH2(CO)(PPh3)3-catalyzed regioselective arylation of aromatic ketones with arylboronates via carbon-hydrogen bond cleavage. 1 Am Chem Soc 127 5936-5945... 

In contrast, N-methylpyrrole underwent direct arylations atthe 3-position [93], and a comparable result was obtained in direct arylations of N-phenylpyrrole employing the electron-deficient rhodium complex 114, in combination with Ag2C03 under microwave irradiation [74b]. Selected examples of regioselective arylations of substituted five-membered heteroarenes are summarized in Table 9.3. 

PALLADIUM-CATALYSED HIGHLY REGIOSELECTIVE ARYLATION OF ELECTRON-RICH OLEFINS... 

Radical reactions. In the presence of air (or oxygen), EtsB promotes radical formation. A tin-free cyclization of w-iodo carbonyl compounds is effected. Regioselective arylation can take advantage of 1,4-aryl migration from tin to a carbon radical center. a-Hydroxyalkylation at C-2 of THF is conveniently accomplished with RCHO. ... 

Palladium-catalyzed reactions have been used to substitute the isoquinoline ring. With the differential reactivity of the 1- and 3-positions of 1,3-dichloroi.soquinoline regioselective arylation at the 3-position is possible <97JGS(P1)927>. The intramolecular Heck reaction of A-2-bromobenzoyl-1-methylene-1,2,3,4-tetrahydroisoquinoline via a 6-ent/o process provides an entry into the protoberberine ring system <97TL1057>. 

Using the data in Figure 2 as a guide, we developed a method for regioselectively arylating AT-alkylindoles. These important substrates rapidly decomposed using the acidic conditions that were optimal for benzofuran... 

However, clear evidence of the IL effect was found for the regioselective arylation of olefins. It is generally accepted that the Heck reaction may proceed via two pathways, a neutral pathway leading to the preferential formation of linear olefins and an ionic counterpart more likely to give rise to branched olefins. Thus, Pd(OAc)2 and l,3-bis(diphenylphosphino)propane (DPPP) immobilized in [G4GiIm]BF4 promote the exclusive a-arylation of several classes of electron-rich olefins with a wide range of aryl iodides and bromides in the absence of halide scavengers (Scheme 3). ... 

A possible solution for functionalization of allylic acetates involves the application of hypervalent iodones (21) as aryl source in the presence of a weak base (NaHCOj) and pincer complex (la) catalysis (Figure 4.12) [49]. Under these conditions, a regioselective arylation of the alkene takes place without altering the allylic acetate functionality. 

The reactivity of furan derivatives in palladium-catalyzed desulfitative arylation was studied. Alkyl-substituted furan derivatives were successfully coupled with a variety of benzenesulfonyl chlorides using a phosphine-free catalyst regioselective arylation at C-5 of the furan was observed in all cases (14S2515). 

Kim J, Movassaghi M (2011) Concise Total Synthesis and Stereochemical Revision of (-r)-Naseseazines A and B Regioselective Arylative Dimerization of Diketopiperazine Alkaloids. J Am Chem Soc 133 14940... 

Scheme 20 Pd-catalyzed regioselective arylation directed by a carboxamide group featuring a 3,5-dimethylphenyl substituent.

---