Cross-Coupling Reactions of Aryl Pivalates with Boronic Acids

Quasdorf, Kyle W.; Xia, Tian; Garg, Neil K.

doi:10.1021/ja806244b

Cited by 362 publications

(170 citation statements)

References 17 publications

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“…[1] During the past decade, enormous effort has been undertaken, especially in ligand design, [2] to enhance the capability of utilizing relatively inert electrophiles, such as aryl chlorides, [3] tosylates, [4] mesylates, [5] and pivalates, [6] as coupling partners. Yet, investigations on the development and application of new nucleophilic partners in cross-coupling reactions remain limited.…”

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confidence: 99%

Palladium‐Catalyzed Cross‐Coupling of Aryl Halides Using Organotitanium Nucleophiles

Lee

Lam

et al. 2009

Angew Chem Int Ed

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Palladium‐Catalyzed Cross‐Coupling of Aryl Halides Using Organotitanium Nucleophiles

Lee

Lam

et al. 2009

Angew Chem Int Ed

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“…The variety of functional groups on these products provide a great opportunity for further functionalization with various methods. [15] However, the ortho-methoxy-substituent product terminated the transformation, which supposedly resulted from the chelating ability of the substrates.…”

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Rhodium‐Catalyzed Direct Addition of Aryl CH Bonds to N‐Sulfonyl Aldimines

Wang

et al. 2011

Angew Chem Int Ed

271

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Nucleophilic addition of highly reactive aryl Grignard reagents and other related organometallic reagents to carbonyl compounds and their derivatives is a fundamental and important reaction for the construction of CÀC bonds. This approach has been well developed (since early last century) and broadly utilized to synthesize alcohol and amine compounds.[1] Traditionally, the requirement of organohalides as the starting materials to produce the active organometallic reagents causes environmental problems owing to their tedious and sluggish preparation (Scheme 1).[2] As a valuable complementary method, directed ortho metelation (DoM) of functionalized arene compounds has its advantages from a synthetic point of view.[3] Apart from their tedious preparation, both Grignard and DoM approached involve the manipulation of air-and moisture-sensitive reagents and the generation of unwanted salt waste. Recent Friedel-Craftstype direct alkylation of electron-rich arene compounds have been developed. This reaction is catalyzed by a Lewis/ Brønsted acid, however, a limited substrate scope and difficulty in regioselective control were encountered.[4] In comparison, transition metal complexes provide a broader outlook for the development of new transformations that may provide tunable reactivity and selectivity. The transitionmetal-catalyzed addition of CÀH bonds to alkene and alkyne derivatives have been extensively investigated.[5] Meanwhile, significant contributions have been made to the field by the addition of C À H bonds to carbonyl compounds and their derivatives, despite the demand for special additives or limited substrate scope.[6] Herein we demonstrated an "ideal" addition of "inert" aryl CÀH bonds to C=N groups in the absence of any additives and without any undesirable waste under mild and neutral reaction conditions. [7] Our research was inspired by the recent progress on the rhodium/palladium-catalyzed addition of aryl boronic acid towards carbonyl compounds, in which the aryl-metal (metal = Pd or Rh) species was considered as a possible key intermediate formed by the transmetalation. [8] In principle, the high-valent aryl-metal species, either from direct cleavage of the C À H bond through electrophilic substitution or the transmetalation of organometallic reagents should exhibit similar reactivity. Because aromatic electrophilic metalation of arenes with/without directing groups and their applications in CÀC and CÀN bond formation have been well studied, [9] the use of Pd catalysis to investigate CÀH addition to C=N bonds was highly preferred. Although numerous Pd catalysts were tested, the lack of desired product was disappointing. We finally gave up on a palladium-based system.We therefore focused on Rh catalysis because of its credible reactivity in the addition of aryl boronic acid to aldehydes [8a] and imines, [10] as well as direct CÀH transformations.[11] Thus, 2-phenylpyridine (1 a) [9t] and PhCH = NTs (2 a) were selected as model substrates. Different Rh species, including Rh I , Rh II , and Rh III c...

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“…[5] Very recently, our group and Garg independently reported that aryl carboxylates could couple with arylboronic acid derivatives via Ni catalysis. [6] Following studies indicated that coupling of aryl pivalates with organozinc reagents and alkyl Grignard reagents could take place under even milder conditions. [7] This transformation was further expanded to alkenyl pivalates to afford styrene derivatives.…”

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confidence: 99%