Suzuki reactions oxidation

As an example, consider the use of PVPy as a solid poison in the study of poly(noibomene)-supported Pd-NHC complexes in Suzuki reactions of aryl chlorides and phenylboroiuc acid in DMF (23). This polymeric piecatalyst is soluble under some of the reaction conditions employed and thus it presents a different situation from the work using porous, insoluble oxide catalysts (12-13). Like past studies, addition of PVPy resulted in a reduction in reaction yield. However, the reaction solution was observed to become noticeably more viscous, and the cause of the reduced yield - catalyst poisoning vs. transport limitations on reaction kinetics - was not immediately obvious. The authors thus added a non-functionalized poly(styrene), which should only affect the reaction via non-specific physical means (e.g., increase in solution viscosity, etc.), and also observed a decrease in reaction yield. They thus demonstrated a drawback in the use of the potentially swellable PVPy with soluble (23) or swellable (20) catalysts in certain solvents. 

Z-vinyl iodide was obtained by hydroboration and protonolysis of an iodoalkyne. The two major fragments were coupled by a Suzuki reaction at Steps H-l and H-2 between a vinylborane and vinyl iodide to form the C(ll)-C(12) bond. The macrocyclization was done by an aldol addition reaction at Step H-4. The enolate of the C(2) acetate adds to the C(3) aldehyde, creating the C(2)-C(3) bond and also establishing the configuration at C(3). The final steps involve selective deprotonation and oxidation at C(5), deprotection at C(3) and C(7), and epoxidation. 

The two major subunits were coupled by a Suzuki reaction in Step H-3. The Multistep Syntheses synthesis was then completed by reductive opening of the 1,3-dioxane ring, oxidation of the terminal alcohol to the carboxylic acid, carbamoylation, deprotection, and lactonization. 

Pyridine-containing tricyclic compounds have been produced via a sequence consisting of a Suzuki reaction and a subsequent annulation. Gronowitz et al. coupled 2-formylthienyl-3-boronic acid with 3-amino-4-iodopyridine. The resulting adduct spontaneously condensed to yield thieno[2,3-c]-l,7-naphthyridine 59 [47]. They also synthesized thieno[3,4-c]-l,5-naphthyridine-9-oxide (60) in a similar fashion [48]. Neither the amino nor the N-oxide functional group was detrimental to the Suzuki reactions. 

BMIM]BF4 was applied to a Suzuki reaction. The active catalyst was a trico-ordinated [Pd(PPh3)2(Ar)][X] complex that formed after oxidative addition of aryl halide to [Pd(0)(PPh3)4] 211). The hydrophobic ionic liquid does not compete with the unsaturated organic substrate for the electrophilic active metal center. 

Sulfonylurea formation, isocyanate, 65, 66 Sulfuration, see also Lawesson benzoxazine, 471 lithio thiophene, 586 phenothiazine, 532, 533 Suzuki reaction, see Coupling Swem oxidation, 18... 

Stille coupling was also developed in tlie early 1980s and is similar to Suzuki coupling in its sequence. It is used to couple aryl or vinyl halides or triflates with organotin compounds via oxidative addition, transmetallation, and reductive elimination. The oxidative addition reaction has tlie same requirements and preferences as discussed earlier for tlie Heck and Suzuki reactions. The reductive elimination results in formation of tlie new carbon-carbon bond. The main difference is that tlie transmetallation reaction uses an organotin compound and occurs readily without the need for an oxygen base. Aryl, alkenyl, and alkyl stannanes are readily available. Usually only one of tlie groups on tin enters into... 

Isomeric thienonaphthyridines were synthesized using the Suzuki reaction. For example, 2-formyl-3-thiopheneboronic acid (200) with aminopyridines 201 and 202 produced thieno[2,3-c][l,7]naphthyridine (203) and thieno[2,3-c][l,8]naphthyridine (204) (1994JHC11). This method was also used to synthesize (1993H245) isomeric A-oxides 205 and 206 from pyridine A-oxides 207 and 208, respectively. 

The tricyclic skeleton of thieno[3,2-c][l,5]naphthyridine 9-7V-oxidc (263) was constructed (1993H245) in two ways by condensation of aldehyde 256 with pyridine /V-oxide 207 or (in lower yield) by the modified Suzuki reaction of the latter with 3-formylthiophene-2-boronic acid (264). 

While oxidation of the benzenediboronic acids with alkaline hydrogen peroxide affords the corresponding 1,3- and 1,4-dihydroxybenzenes (70-72%), the pyridinediboronic acids lead via a double Pd(0) catalyzed Suzuki reaction with 4-iodoanisole to 2,5- and 2,6-Z /s-(4-methoxyphenyl)pyridines (Sch. 36) [107]. 

On going through the industrial processes described above the question arises of the reasons for the extensive use of palladium. To drive such catalytic processes it is necessary to find a compromise, for example a balance between the tendency of a transition metal to undergo oxidative addition on the one hand and reductive elimination to liberate the organic product on the other. This means that the metal must be sufficiently noble to favour reductive elimination without impairing its ability to undergo a sufficiently fast oxidative addition. In certain cases, as in the Suzuki reaction, the less expensive nickel... 

Suzuki reaction the palladium-catalyzed reaction of an aryl or vinyl halide with an aryl boronic acid to give an arylated or vinylated arene. In some cases, primary alkyl halides can react in place of the aryl or vinyl halides Wacker process the palladium-catalyzed oxidation of ethene to acetaldehyde by oxygen... 

When the Stille reaction is carried out under a CO atmosphere, the carbonylative coupling proceeds in a manner similar to that described for the Suzuki reaction namely, carbonyl insertion into the Pd-C bond of the oxidative addition complex. Transmetalation, followed by ds-trans-isomerization and reductive elimination, generates the ketone product. " ... 

Kirchhoff, J. H., Netherton, M. R., Hills, I. D., Fu, G. C. Boronic Acids New Coupling Partners in Room-Temperature Suzuki Reactions of Alkyl Bromides. Crystallographic Characterization of an Oxidative-Addition Adduct Generated under Remarkably Mild Conditions. J. Am. Chem. Soc. 2002, 124, 13662-13663. 

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