Construction of Pyridine Rings by Metal-Mediated [2 + 2 + 2] Cycloaddition

Varela, Jesús A.; Saá, Carlos

doi:10.1021/cr030677f

Cited by 740 publications

(243 citation statements)

References 63 publications

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“…The reaction only proceeded with derivatives of Meldrums acid in water in the presence of CuA C H T U N G T R E N N U N G (OAc) 2 and sodium ascorbate [Eq. (30)]. [84] The Cu(II) salts were reduced to Cu(I) salts in the presence of sodium ascorbate, and thus would not lead to a facile generation of Cu(I)-alkynylide which participates in oxidative acetylide coupling.…”

Section: Conjugate Additionmentioning

confidence: 99%

“…Later, they employed a copper catalyst together with the chiral PINAP ligand 5 to develop an enantioselective version of this addition reaction and achieved 82-97 % ee of products with useful yields [Eq. (30)]. [85] Li et al reported the first palladium-catalyzed 1,4-addition of terminal alkynes to vinyl ketones in water with high yields [Eq.…”

Section: Conjugate Additionmentioning

confidence: 99%

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Catalyzed Reactions of Alkynes in Water

Chen

2006

Adv Synth Catal

123

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Section: Conjugate Additionmentioning

confidence: 99%

Section: Conjugate Additionmentioning

confidence: 99%

Catalyzed Reactions of Alkynes in Water

Chen

2006

Adv Synth Catal

123

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“…tBu 4 ZnLi 2 has been shown to be highly selective for the performance of iodine or bromine exchanges [58,59]. Additionally, the use of tBu 4 ZnLi 2 ·TMEDA allows to carry out the metalations at room temperature.…”

Section: Regioselective Functionalization Of Pyridines Via a Halogen/mentioning

confidence: 99%

Review. Regioselective Functionalization of Pyridines using a Directed Metalation or a Halogen/Metal Exchange

Manolikakes

Barl

Sämann

et al. 2013

Zeitschrift Für Naturforschung B

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This review describes the various ways of functionalizing the pyridine scaffold using either directed metalation or halogen/metal exchange. Deprotonation can be accomplished with different lithium amides or alkyllithium reagents at low temperature. Milder conditions and higher functional group tolerance can be achieved by using ate-bases with different metals (Cd, Mg, Zn) or TMP (2,2,6,6-tetramethylpiperidyl) metal reagents (metal = Mg, Zn, Zr). With alkyllithium reagents it is also possible, by carefully adjusting the reaction conditions, to perform bromine/lithium exchange reactions. Organomagnesium reagents, like iPrMgX (X = Br, Cl·LiCl), may be used for exchanging more sensitive iodinated or brominated pyridines.

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“…Transition metal-catalyzed [2+ 2+2] cycloaddition of unsaturated compounds, such as alkynes, nitriles, alkenes, imines and isocyanates, is the most atom-economical protocol for the synthesis of six-membered ring compounds [61][62][63][64][65][66][67][68][69][70][71][72][73][74]. Although various types of catalysts and substrates have been subjected to the inter-and intramolecular reactions, the development of iron-catalyzed [2+2+2] cycloadditions was very slow and the substrates were mainly focused on the alkynes and nitriles.…”

Section: Construction Of Six-membered Ringsmentioning

confidence: 99%

Recent advances in the iron-catalyzed cycloaddition reactions

Wang

Wan

2012

Chin. Sci. Bull.

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The rapid generation of molecular in a relatively easy manner has made the cycloaddition reaction a powerful tool in the synthesis of different membered ring compounds. Clearly, iron catalysts are becoming a much more interesting and viable choice for this purpose. In this review, a number of promising results in the iron catalyzed cycloaddition reactions in the last decades were summarized. Special attention has been paid to the asymmetric cycloaddition reactions. cycloaddition, iron catalyst, asymmetric Citation:Wang C X, Wan B S. Recent advances in the iron-catalyzed cycloaddition reactions. Chin Sci Bull, 2012, 57: 23382351, doi: 10.1007/s11434-012-5141-z Cycloaddition reaction, which can construct several bonds simultaneously in a single step, is one of the most powerful strategies for the synthesis of cyclic compounds from various unsaturated substrates such as alkynes, alkenes, allenes, nitriles, aldehydes, ketones, imines, etc. Three-, four-, five-, six-or seven-membered rings are obtained through these transformations. The high atom-efficiency, as well as the good tolerance of different functional groups, continues to draw many chemists' attention to this field. In particular, great efforts have been devoted to the development of novel and efficient catalytic systems. However, harsh reaction conditions are often required including heat, light, high pressure or sonication, and the lack of chemo-and/or regioselectivity is also an important problem. Over the past decades, the use of transition metal catalysts has contributed significantly to the development of the cycloaddition reactions and good selectivities were obtained [1]. Among all the available transition metals, iron is generally regarded as one of the most inexpensive, abundant, benign and relatively non-toxic metals [2]. Many transformations have been effectively promoted by iron catalysts, and excellent reviews on the iron-catalyzed reactions are available [3][4][5][6][7][8][9][10][11][12][13][14][15]. Bolm and co-workers [3] summarized the most important transformations with the aid of iron catalysts in 2004, including addition, substitution, cycloaddition, reduction and other reactions. At a later time, they also reviewed the oxidative C-C coupling reactions [4] and the development of carbon-heteroatom and heteroatom-heteroatom bond formation under iron catalysts [5]. The uses of FeCl 3 as catalyst in organic synthesis were covered by Padrón [6] and Bolm [4], and the cross coupling reactions were discussed in detail by Fürstner [7,8]. Recently, direct C-H transformation via iron catalysis was summarized by Shi and co-workers [9]. Applications of iron catalysts on other reactions were also summarized by Bauer [10] However, despite the aforementioned contributions, reviews mainly focus on the iron-catalyzed cycloaddition reactions are rather rare [15]. In this review, we will point out recent advances in this field, most contributions going from 2004 to Nov. 2011. Although every effort has been made to avoid repetition, some overlap with the ...

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Construction of Pyridine Rings by Metal-Mediated [2 + 2 + 2] Cycloaddition

Cited by 740 publications

References 63 publications

Catalyzed Reactions of Alkynes in Water

Catalyzed Reactions of Alkynes in Water

Review. Regioselective Functionalization of Pyridines using a Directed Metalation or a Halogen/Metal Exchange

Recent advances in the iron-catalyzed cycloaddition reactions

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