Cross-coupling reactions benzylation

The cross-coupling reactions of benzylic halides and acyl halides produced the expected ketones in good to high yields(39,47). The present method can supplement the corresponding Grignard reaction, which does not work well since benzylmagnesium halides undergo dimerization readily. 

The Suzuld-Miyaura cross-coupling reaction of 9-benzyl-6-chloropurine with boronic acids gives 6-alkylated purines in moderate to excellent yields. The reaction has been successfully... 

In 1991, Inanaga achieved Sml2-mediated intermolecular cross-coupling between C=0 (ketones or aldehydes) and C=N by using 0-benzyl formaldoxime as a C=N component7 The reaction requires HMPA as a co-solvent and a suitable proton source such as /-butyl alcohol or ethylene glycol. A cross-coupling reaction between ketones and... 

In Table 1 containing 72 (= 9 x 8) classes of cross-coupling reactions, 42 of them, nearly 60% of the total, involve the use of at least one allyl, benzyl or propargyl (or allenyl) reagent as a cross-coupling partner. They can be divided into five categories corresponding to the five blocks in Table 1, as shown below. 

Scheme8.3. Simplified mechanism of Pd-catalyzed cross-coupling reactions. R, R = aryl, vinyl, a I kynyl, allyl, benzyl, alkyl, acyl ...

Chen, H. Deng, M.-Z. A novel Suzuki-type cross-coupling reaction of cyclopropylboronic esters with benzyl bromides./. Chem. Soc. Perkin Trans. 1 2000, 1609-1613. 

Most recently, Monteiro et al. have reported that cyclopalladated compounds derived from the ortho-metalation of benzylic tert-butyl thioethers are excellent catalyst precursors for the Suzuki cross-coupling reaction of aryl bromides and chlorides with phenylboronic acid under mild reaction conditions. A broad range of substrates and functional groups are tolerated in this protocol, and high catalytic activity is attained (Eq. (58)) [93]. 

Stille coupling between suitable 6-chloropurines and aryl(tributyl)tin afforded 6-arylpurines with a variety of substituents in the 9-position which were screened for antimycobacterial activity <02JMCI383>. The Stille cross-coupling reactions of 1,4- and l,3-bis(trialkylstannyl)benzenes with 9-benzyl-6-chloropurine gave 1,4- and l,3-bis(purin-6-yl)benzenes and 4-(purin-9-yl)benzenes <02T7431>. 

Reaction of aryl Grignard compounds, obtained in situ by iodine-magnesium exchange, with C0CI2, presumably generates aryl radicals. In the presence of a double bond or aromatic ring an intramolecular radical cyclization may take place. This reaction was used for the synthesis of spiro-indolines.244 Oshima has applied cobalt-mediated tandem radical cyclization-cross-coupling reaction for the synthesis of benzyl-substituted heterocycles (Scheme 80).245... 

Another, mechanistically closely related reaction is the cross-coupling reaction of aryl, benzyl, vinyl, or allyl halides with organometallic coupling reactions, such as Grignard reagents or, preferably, less reducing organometallics such as tin compounds or boronic acids RB(OH)2 the latter allow the reaction to be conducted even in aqueous media.83 The principal reaction steps are ... 

The Suzuki cross-coupling reaction between 1,2,5-trisubstituted pyrrole halides 1443 and 2-A -(/-butoxycarbonyl)-aminophenyl boronic acid 1444 performed with benzyl[bis(triphenylphosphine)]palladium(ll) chloride (PdBnCl(PPh3)2)... 

Figure 3.63). The palladium(II) complex was used in the Suzuki-Miyaura cross-coupling reaction between phenylboronic acid and benzyl bromide, 2-bromo and 4-bromo benzalde-hyde, respectively [180-182],...

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