Selective cross-coupling

With the bisoxazoline hgand (S)-Phbox and CuCl, the asymmetric oxidative couphng of 2-naphthol and hydroxy-2-naphthoates resulted in an asymmetrically substituted 2,2 -binaphthol with ee s of up to 65% [260]. On the basis of the previous results obtained with this catalyst system, the asymmetric oxidative cross-coupling polymerization of 2,3-dihydroxynaphthalene [261] and methyl 6,6 -dihydroxy-2,2 -binaphthalene-7,7 -dicarboxylate [262] as well as the copolymerization of 6,6 -dihydroxy-2,2 -binaphthalene and dihexyl 6,6 -dihydroxy-2,2 -binaphthalene-7,7 -dicarboxylate with Cu diamine catalysts were carried out imder aerobic conditions, using O2 as the oxidant, and a cross-coupling selectivity of 99% was achieved [263]. 

Table 8.2 shows the results of the cross-coupling reaction between two differently substituted 2-naphthol derivatives using the CuCl-(5)Phbox catalyst. In conclusion, the first catalytic asymmetric oxidative coupling with a high cross-coupling selectivity was accomplished under mild conditions. 

Highly selective cross-coupling benzoin condensations have been achieved via the use of enzymatic methods. ... 

When applied to polyfunctional substrates, iron catalyzed reactions allow either for selective, exhaustive, or consecutive cross-coupling processes to be carried out in "one pot."... 

These processes have flourished, mainly due to their selectivity and versatility, to the point where cross-coupling chemistry is often the initial thinking of organic chemists in synthetic and retro-synthetic approaches [2]. In fact, nowadays it is difficult to find a contribution in fine chemical or natural product synthesis where these molecular assembly tools are not employed. This is often due to the simple preparation and handling of the reaction partners as well as their relative compatibility with several functional groups. 

The 121/Cl3SiH combination selectively cross-couples alkenes with alkynes intermolecularly to give acyclic homoallylic silanes 127 and 128 (Eq. 22) [73]. 

Cross-coupling reactions with Zn acetylenides are the most convenient and selective routes to terminal acetylenes. In this reaction Zn is markedy superior to other metals, including Sn (24).116 The higher reactivity of Zn acetylides allowed assembly of hexaethynylbenezenes in two steps, with the last three groups introduced at the second stage by the Negishi reaction (25).117... 

Aryl-alkenyl cross-coupling is straightforward. Simple alkylmagnesium reagents (Me, Et, CH2SiMe3, etc.) can be easily involved in Ni-catalyzed cross-coupling (27),139,140 while more complex alkyl halides—particularly branched ones prone to /3-hydride elimination—require Pd catalysts with bidentate phosphines, such as dppf, to achieve good selectivity (Section 9.6.3.4.7). 

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