Chemo‐, Regio‐, and Stereoselective Cobalt‐Mediated [2+2+2] Cycloaddition of Alkynyl Boronates to Alkenes: 1,3‐ and 1,4‐Diboryl‐1,3‐cyclohexadienes

Gandon, Vincent; Lebœuf, David; Amslinger, Sabine; Vollhardt, K. Peter C.; Malacrìa, Max; Aubert, Corinne

doi:10.1002/anie.200502038

Cited by 56 publications

(23 citation statements)

References 70 publications

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“…[12] Remarkably, the diyne 1 q, not tested previously, transformed in the presence of [CpCoA C H T U N G T R E N N U N G (C 2 H 4 ) 2 ] not only to the expected 8 (16 %), but also to triene complexes 9 (24 %) and 10 (24 %). These complexes were separable by chromatography and fully characterizable, an exercise greatly aided by their relative stability.…”

Section: Wwwchemeurjorgmentioning

confidence: 94%

“…Again extending prior work, [12] the initial focus was on the use of alkynyl borates. The results re-emphasize the energetic closeness of the three regiochemical pathways for alkyne oxidative coupling, and the ensuing competition toward cyclic versus acyclic products ( Table 2).…”

Section: Wwwchemeurjorgmentioning

confidence: 99%

“…[12] It is of relevance that [CpCoA C H T U N G T R E N N U N G (C 2 H 4 ) 2 ], [13] on its own, furnished products of ethene incorporation, whereas added alkenes outcompeted ethene in the cyclization. Moreover, variation of the tether lengths in a range of a,w-diynes from 3 to 5 atoms did not alter the outcome of this process.…”

Section: Introductionmentioning

confidence: 99%

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Cobalt‐Mediated Linear 2:1 Co‐oligomerization of Alkynes with Enol Ethers to Give 1‐Alkoxy‐1,3,5‐Trienes: A Missing Mode of Reactivity

Lebœuf

Iannazzo

Geny

et al. 2010

Chemistry A European J

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A variety of 1,6-heptadiynes and certain borylalkynes co-oligomerize with enol ethers in the presence of [CpCo(C(2)H(4))(2)] (Cp=cyclopentadienyl) to furnish the hitherto elusive acyclic 2:1 products, 1,3,5-trien-1-ol ethers, in preference to or in competition with the alternative pathway that leads to the standard [2+2+2] cycloadducts, 5-alkoxy-1,3-cyclohexadienes. Minor variations, such as lengthening the diyne tether, cause reversion to the standard mechanism. The trienes, including synthetically potent borylated derivatives, are generated with excellent levels of chemo-, regio-, and diastereoselectivity, and are obtained directly by decomplexation of the crude mixtures during chromatography. The cyclohexadienes are isolated as the corresponding dehydroalkoxylated arenes. In one example, even ethene functions as a linear cotrimerization partner. The alkoxytrienes are thermally labile with respect to 6pi-electrocyclization-elimination to give the same arenes that are the products of cycloaddition. The latter, regardless of the mechanism of their formation, can be viewed as the result of a formal [2+2+2] cyclization of the starting alkynes with acetylene. One-pot conditions for the exclusive formation of arenes are developed. DFT computations indicate that cyclohexadiene and triene formation share a common intermediate, a cobaltacycloheptadiene, from which reductive elimination and beta-hydride elimination compete.

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Section: Wwwchemeurjorgmentioning

confidence: 94%

Section: Wwwchemeurjorgmentioning

confidence: 99%

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Cobalt‐Mediated Linear 2:1 Co‐oligomerization of Alkynes with Enol Ethers to Give 1‐Alkoxy‐1,3,5‐Trienes: A Missing Mode of Reactivity

Lebœuf

Iannazzo

Geny

et al. 2010

Chemistry A European J

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“…The application of alkynylboronates and Co complexes as catalysts in the synthesis of cyclohexadienes has been described recently. [15] Treating CpCoA C H T U N G T R E N N U N G (C 2 H 4 ) 2 with alkynylboronates under an atmosphere of ethene, resulted in the formation of 1,3-and 1,4-diboryl-(h 4 -1,3-cyclohexadiene), along with 1,2-and 1,3-diboryl-(h 4 -cyclobutadiene) complexes. These novel complexes were air-stable and purified by column chromatography.…”

Section: Synthesis Of 13-cyclohexadiene Derivativesmentioning

confidence: 99%

[2+2+2] Cycloaddition Reactions Catalyzed by Transition Metal Complexes

2006

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Recent progress in the synthesis of benzene and 1,3-cyclohexadiene derivatives, and heterocyclic compounds such as pyridines, pyridones, pyrans, pyrimidine diones, etc, has been reviewed. The general mechanistic aspects of the [2 + 2 + 2] cycloaddition reaction are discussed. The asymmetric variants of these reactions are also discussed along with the proposed models of asymmetric induction. Keywords: arenes; catalysis; cycloaddition; heterocycles; metallacycles; transition metals IntroductionThe significance and increasing popularity of [2 + 2 + 2] cycloaddition reactions is evident from the number of reviews that have recently appeared in the literature. [1][2][3] The [2 + 2 + 2] cycloaddition reaction is remarkable in terms of its ability to utilize various unsaturated substrates such as alkynes, diynes, alkenes, imines, isocyanates, isothiocyanates, and CO 2 in the synthesis of a broad variety of highly substituted cyclic molecules such as benzenes, pyridines, pyridones, 1,3-cyclohexadienes, pyrones, thiopyridones and cyclohexanes. Multisubstituted benzenes and pyridines have traditionally been synthesized by aromatic electrophilic substitution (AES) reactions and a variety of metal-mediated coupling reactions. Although, these reactions are extremely efficient, they generally involve multistep syntheses. The application of AES reactions in the synthesis of polysubstituted aromatic rings is limited by the effect of the substituent groups and, hence, it may be very difficult or even impossible to add various functionalities at a specific position on the aromatic ring. On the other hand, [2 + 2 + 2] cycloaddition reactions are extremely atom-efficient and involve the formation of several C À C bonds in a single step. Another important feature of the [2 + 2 + 2] cycloaddition reaction is tolerance of a myriad of functional groups such as alcohols, amines, alkenes, ethers, esters, halogens, and nitriles. Moreover, the availability of numerous catalytic systems that have Adv. Synth. Catal. 2006, 348, 2307 -2327 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2307 REVIEWS been efficient in tedious syntheses highlights the applicability of the [2 + 2 + 2] cycloaddition reaction. These are important requirements for the [2 + 2 + 2] cycloaddition reaction to become a universal synthetic tool for the synthesis of benzene, pyridine, and other cyclic derivatives. An important problem with the [2 + 2 + 2] cycloaddition reaction is the lack of chemoand regioselectivity observed in earlier reported reactions. However, significant effort has been focused on attaining a high degree of chemo-, regio-and even enantioselectivity with considerable success as evident from recent reports. Excellent reviews on [2 + 2 + 2] cycloaddition reactions are available. Kotha and co-workers have reviewed the synthesis of benzene derivatives by the cyclotrimerization of three alkyne functionalities utilizing transition metal systems as catalysts.[1] Their review is divided into: (a) intermolecular reactionsin which the three pi (alkyn...

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“…

Benzannulation reactions are one of the most efficient and direct methods for assembling highly substituted aromatic compounds. [2] Indeed, such compounds have been accessed by benzannulation techniques involving transition metal catalysis [3] and pericyclic [4] processes.Our preliminary work in this area showed that the Dötz benzannulation reaction could be exploited to access quinone boronic esters in good yield and with excellent levels of regiocontrol. With regard to exploiting such reactions for the production of synthetically useful organic compounds, aromatic boronic acids represent an important target as they are widely acknowledged as being amongst the most useful and versatile intermediates in synthetic chemistry.

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confidence: 99%

A Nickel‐Catalyzed Benzannulation Approach to Aromatic Boronic Esters

Auvinet

Harrity

2011

Angew Chem Int Ed

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Off and on: A nickel‐catalyzed benzannulation of alkynylboronates provides functionalized phenols with high levels of chemo‐ and regioselectively. While transmetalation of organoboron intermediate to organonickel does not occur during cycloaddition, it is “switched on” by addition of base, thus allowing a one‐pot benzannulation and cross‐coupling to be realized (see scheme; Pin=pinacolato, Ms=mesyl).

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Chemo‐, Regio‐, and Stereoselective Cobalt‐Mediated [2+2+2] Cycloaddition of Alkynyl Boronates to Alkenes: 1,3‐ and 1,4‐Diboryl‐1,3‐cyclohexadienes

Cited by 56 publications

References 70 publications

Cobalt‐Mediated Linear 2:1 Co‐oligomerization of Alkynes with Enol Ethers to Give 1‐Alkoxy‐1,3,5‐Trienes: A Missing Mode of Reactivity

Cobalt‐Mediated Linear 2:1 Co‐oligomerization of Alkynes with Enol Ethers to Give 1‐Alkoxy‐1,3,5‐Trienes: A Missing Mode of Reactivity

[2+2+2] Cycloaddition Reactions Catalyzed by Transition Metal Complexes

A Nickel‐Catalyzed Benzannulation Approach to Aromatic Boronic Esters

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