Internal arylations

Oxidative Heck arylation of enamides with arylboronic acids, using oxygen gas as a reoxidant for Pd(0) and 2,9-dimethyl-1,10-phenanthroline as a chelating regiocontrolling ligand, yielded a (= internally) arylated reaction product as the major compound with a very good a//3 selectivity [92]. Microwave irradiation with prepressurized sealed vials proved useful in reducing the reaction time (Scheme 82). 

Regioselectivities that are usually high to excellent have been reported in novel palladium-catalyzed Heck arylation reactions with a variety of allylic substrates. The //-stabilizing effect of silicon enhanced regiocontrol in the internal arylation of allyl-trimethylsilane (Eq. 11.5) [18], and coordination between palladium and nitrogen... 

Equation 11.9 Internal arylation of butyl vinyl etherwith bromo-benzene. 

Table 1. Hydroarylation of internal aryl-substituted alkynes with mesitylene l.a...

Internal aryl-substituted alkynes also undergo Au(111)-catalyzed hydroarylation with electron-rich alkynes (Table 1) [2, 4]. The reactivity of diphenylactylene, however, is very low. 

The use of <7-2,4-dinitrophenyl oximes has lead to a novel method for the generation of alkylideneaminyl radicals by a one-electron transfer process from phenol derivatives. These species thus generated are smoothly captured with an internal aryl or olefin moieties. This represents a new, very useful tool for the preparation of nitrogen-containing heterocycles. 

Arylation of butyl vinyl ether with an arylpalladium chloride complex predominantly delivers the terminally arylated product (as expected if a neutral oxidative addition complex is involved). Internal arylation of the highly polarized vinyl ether dominates with the corresponding iodide precursor, suggesting that in this case the cationic intermediate is more plausible as the key intermediate. ... 

Figure 1.6 Pd-mBDPP-catalyzed regioselective internal arylation of electron-rich olefins by aryl halides. (Reproduced with permission from Ref [43].)...

There are two major realizations of the polar pathway in intermolecular Mizoroki-Heck reactions (1) enantioselective arylation of cyclic alkenes (Chapter 11) and (2) regioselective internal arylation of terminal alkenes (Chapter 3). 

Figure 3.14 Polar solvents in combination with ammonium salts promote internal arylations.

An illustrative example of the great applicability of Mizoroki-Heck chemistry is presented in Figure 3.17, where the required indanone moiety is constructed in a one-pot manner starting with an internal arylation. The aminoindanone was obtained in optically... 

Figure 3.16 Preparation of a cyclic HIV-1 protease inhibitor employing a regioselective internal arylation with consecutive hydrolysis.

Figure 3.33 internal arylation of allyl alcohol and allyl ethyl ether. 

InternahTerminal 98 2 Figure 3.36 internal arylation of allyltrimethylsilane with aryl triflates. 

Figure 3.37 Internal arylation of allyltrimethylsilane with aryl bromides in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmimUBF4j).

IntemalTerminal >99.5 0.5 Figure 3.38 Internal arylation of a primary ally I amine equivalent. 

Olofsson, K., Lathed, M. and Hallberg, A. (1998) Highly regioseleclive palladium-catalyzed internal arylation of aUyltrimethylsilane with aryl triflates. J. Org. Chem., 63, 5076-9. 

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