Palladium carbonylative cross-coupling

Indolylborates 142 (Z = Me, Boc, OMe), available via regioselective C-2 lithiation of indoles 141, are capable of undergoing palladium-catalyzed carbonylative cross-coupling... 

Recent contributions from Vogel s group have shown that, under CO atmosphere and in the presence of Pd2(dba)3 and Ph3As, 1-stannyl glycals can be carbonylated and coupled to organic halides (Scheme 6a),38 or vinyl triflates (Scheme 6b),39 in carbonylative Stifle cross-coupling processes.40 Also of interest is the palladium catalyzed cross-coupling reaction of... 

Additional examples of palladium-catalyzed cross-couplings, in particular with allenylzinc compounds, can be found elsewhere [11, 15, 36]. A systematic study comparing several chiral palladium phosphine catalysts in the reaction of 4,4-di-methyl-1,2-pentadienylzinc chloride and iodobenzene revealed that an enantiomeric excess of only 25% was obtained from the best catalyst combination PdCl2 and (R,R)-DIOP [15]. The synthetic value of these transformations of donor-substituted allenes as precursors is documented by the preparation of a/l-unsaturatcd carbonyl... 

A prototypical study for this section has been obtained as early as in 1983 for carbonylative cross-coupling of the mixture of aryl iodide and alkyl iodide in the presence of Zn metal and palladium catalyst. This system apparently works due to differences of reactivity of aryl versus alkyl iodide toward metallation by Zn. Further studies were rather scarce to involve only preformed functionalized alkylzincs. Carbonylative cross-coupling of functionalized organozinc reagents with allylic esters and GO (1 atm) can be carried out in THF in the presence of HMPA, which suppresses side-reactions (Scheme 4). ... 

Alkenyliodonium salts can be used as highly reactive substrates for Heck-type olefination and similar palladium-catalyzed cross-coupling reactions [63 -65]. In a recent example, a series of dienes 80 were stereo- and regioselectively prepared by a palladium-catalyzed Heck-type reaction of alkenyliodonium salts 79 with a,/3-unsaturated carbonyl compounds (Scheme 37) [64]. 

However, for other palladium catalysed reactions of organozinc iodides with electrophiles, THF is a good choice of solvent. The incompatibility of THF and acid chlorides at ambient temperature can also be overcome, in some cases, by the use of a carbonylative cross-coupling in which an iodobenzene derivative is used as the precursor.17... 

The application of organozinc iodides prepared in THF is illustrated in Protocols 4 and 5, which describe the palladium catalysed cross-coupling of a serine-derived organozinc iodide with a vinyl iodide, and the palladium catalysed carbonylative cross-coupling of another serine-derived organozinc iodide with a functionalized aromatic iodide. In the reaction with the vinyl iodide, it is important to transfer the solution of the organozinc iodide from the residual zinc, since this can react unproductively with the electrophile. In the case of the carbonylative coupling with the functionalized aromatic iodide, such a transfer is unnecessary, since the zinc does not react with the electrophile under the reaction conditions. These two protocols also illustrate how to conduct such reactions on different scales. 

Diaryliodonium salts are viable alternatives to aryl halides for palladium-catalyzed cross-coupling reactions (02CRV2523). In the area of heterocyclic synthesis, Pd(II)-catalyzed carbonylation of diaryliodonium... 

Keywords. Organotin compounds. Palladium catalyst. Cross-coupling reaction, Carbonylative coupling... 

For the ketone synthesis via the present protocol, acid chlorides are useful precursors, in deed. Nevertheless, carbonylative cross coupling with organic halides is strategically the most simple and direct way to this purpose. The palladium-catalyzed carbonylative cross-coupling reaction with various organic halides has been extensively investigated, because of its merits from synthetic as well as phenomenal point of view. Acid chlorides are not always readily available, and their preparation is not always compatible with many sensitive functionalities. Therefore the development of this type of reaction widens the scope of the ketone synthesis in the present protocol because of the ready availability and storability of organic halides and pseudohalides. 

Ishiyama, T., Takagi, J., Kamon, A., Miyaura, N. Palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with vinyl trifiates -substituted by a carbonyl group efficient synthesis of -boryl- -unsaturated carbonyl compounds and their synthetic utility. J. Organomet. Chem. 2003, 687, 284-290. 

An indium-mediated radical cyclization sequence has been used to synthesize stereoselectively 3-alkylideneoxindoles [65, 66]. The generation of predominantly the i -isomer, such as seen with 96 below, is attributed to the strong coordination of the indium to the carbonyl of the oxindole intermediate, and the transformation of various iodo-ynamides to the cyclized oxindoles occurred in good yield. Selective approaches to the E- and disubstituted 3-alkylideneoxindoles involving a tandem palladium-catalyzed cross coupling reaction were also highlighted in this report. 

In summary, we have summarized representative examples of transition-metal-catalyzed carbonylative domino reactions. In the area of carbonylations, palladium, rhodium, and cobalt are still the main actors. The abihty of palladium catalysts in carbonylative cross-coupling, rhodium catalysts in carbonylative C-H activation, and cobalt catalyst in carbonylative reactions with unsaturated bonds is impressive. 

Aryl ketones were formed from the Cr(CO)3 complex of (trialkylstannyl)ben-zene or chlorobenzene by a palladium-catalyzed cross-coupling reaction in the absence of external CO. The Cr(CO)3 moiety provides the required CO predominantly by an intramolecular mechanism. However, non-carbonylation products were also observed. 

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