Boronate esters, Suzuki coupling

Suzuki Coupling Reaction (IV). The coupling of boronic acid (II) with iodooxazole (III) was the first Suzuki reaction done on-scale at Bristol Myers Squibb. Our hope from the beginning was to isolate isopropyl ester of the coupled biaryl, so that issues related to removal of Pd can be separated from other quality issues of the coupling reaction as outlined in Scheme 3. 

In addition, arylthiophene 70 was obtained by a one-pot Suzuki coupling of p-methoxyiodobenzene and 3-bromothiophene via an in situ boronate formation using one equivalent of the thermally stable diborane 69 [55], This method avoids the isolation of boronic acids and is advantageous when base-sensitive groups such as aldehyde, nitriles and esters are present. However, the cross-coupling yields are low when both aryl halides are electron-poor because of competitive homocoupling during the reaction. 

Scheme 7.10 Polyglycerol boronic esters as high-loading soluble reagents for Suzuki cross-coupling reactions.

Even esters can be ortholithiated, provided the electrophile is present in situ during the hthiation. Neopentyl ester 160 gives, on treatment with LDA in the presence of triisopropylborate, the boron derivative 161, which can be deprotected and used in Suzuki coupling reactions (Scheme 79) . Less hindered esters can also be successfully orthohthiated in the presence of a boron electrophile (Scheme 80) . ... 

Vinylsilanes react with boron trichloride to give the corresponding borodesilylation products in good yield which, in turn, can be transformed into boronic esters 124 by alcoholysis (equation 102). The initial dichloroorganoborane products can be used directly in the Suzuki-Miyaura cross-coupling reaction192. Replacement of a carbon-silicon bond by a carbon-tin bond in fluorinated alkenes (e.g. 125) can be achieved by the reaction of silanes with Bu3SnCl and KF in DMF under mild conditions (equation 103)193. It is... 

The Suzuki Coupling, which is the palladium-catalysed cross coupling between organoboronic acid and halides. Recent catalyst and methods developments have broadened the possible applications enormously, so that the scope of the reaction partners is not restricted to aryls, but includes alkyls, alkenyls and alkynyls. Potassium trifluoroborates and organoboranes or boronate esters may be used in place of boronic acids. Some pseudohalides (for example triflates) may also be used as coupling partners. 

Milkiewicz and coworkers [16] prepared a series of novel tetra-substituted furo[3,2-b Ipyrroles from the methyl or ethyl 3-bromo-2-phcnyllliro 3,2-/ pyrrole-5-carboxylate 40, which was prepared from 3-bromo-2-phenylfuran-2-carbaldehyde 39. The compounds 40 were subjected to a Suzuki coupling with 4-chlorophenyl boronic acid to form 41, which was treated with a variety of alkylating agents to afford the corresponding esters 42. The esters were then saponified to acids 43 (Scheme 6). 

The domino Suzuki coupling-Heck reaction sequence involving dihydroaromatic alkenyl-substituted boronic esters (186) with diiodobenzene, bromoiodobenzene, or iodoaniline derivatives yields substituted phenanthrene (187) and phenanthridene derivatives regiospecifically (Scheme 52).218... 

The Suzuki reaction is a palladium-catalyzed substitution that couples an aryl or vinyl halide with an alkyl, alkenyl, or aryl boronic acid or boronate ester. Many variations on this fundamental reaction are possible, containing a wide variety of functional groups. 

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