Formal [4+2] cycloaddition of cyclobutanones bearing alkyne–cobalt complex at their 3-positions

Kawano, Mizuki; Kiuchi, Takaaki; Matsuo, Jun‐ichi; Ishibashi, Hiroyuki

doi:10.1016/j.tetlet.2011.11.067

Cited by 13 publications

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References 17 publications

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“…196 A formal [4+2] cycloaddition of a cyclobutanone derivative, such as 95, was observed by Matsuo in the synthesis of pyranone derivatives 96 (Scheme 58). 197 The best results were obtained when SnCl 4 was applied as Lewis acid while other Lewis acids such as BF 3 •OEt 2 , TiCl 4 and EtAlCl 2 led to inferior results. In addition to aromatic aldehydes, aliphatic aldehydes could also be applied with good success for the formation of the cis-isomers as the predominant stereoisomer.…”

Section: Scheme 57mentioning

confidence: 99%

Cobalt-Catalysed Bond Formation Reactions; Part 2

Röse

Hilt

2015

Synthesis

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This review summarises the cobalt-catalysed reactions of the years 2008 through 2014. Covered are addition reactions, such as the hydrogenation of double bonds, the addition of C-H bonds to double and triple bonds, C-H activation reactions, cobalt-catalysed cross-coupling reactions and selected additions of H-B and H-Si bonds to unsaturated starting materials. The cobalt-catalysed cycloadditions range from cyclopropanations, [2+2], Pauson-Khand reactions, [2+2+2], [4+2], [6+2] cycloadditions as well as benzannulations. Also covered are Nicholas reactions, cobalt-catalysed Jacobsen's kinetic resolution of epoxides as well as selected miscellaneous cobalt-catalysed processes mainly for carbon-carbon bond formations. 1 Introduction 2 Addition Reactions 3 Homo-and Cross-Coupling Reactions 4 Jacobsen Kinetic Resolution of Epoxides 5 Nicholas Reactions 6 Cycloaddition Reactions 7 Miscellaneous 8 Conclusion

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Section: Scheme 57mentioning

confidence: 99%

Cobalt-Catalysed Bond Formation Reactions; Part 2

Röse

Hilt

2015

Synthesis

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“…[14] They prepared cyclobutanones bearing alkynecobalt complex 24 in seven steps [13] as model substrates to probe their hypothesis (Scheme 8). [15] After screening a series of catalysts, tin(IV) chloride was found to be the most suitable Lewis acid to catalyze the formal [4+2] cycloaddition effectively. In all examples, the cycloaddition reaction was highly cis selective.…”

Section: Prevalent Approaches To 3-ethoxycyclobutanones and Derivativesmentioning

confidence: 99%

3‐Alkyloxycyclobutanones as Useful Synthons for Heterocycle and Carbocycle Synthesis

et al. 2014

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Substituted 3-alkyloxycyclobutanones are highly valuable intermediates in organic synthesis, which demonstrate interesting and rich reactivity in different types of reactions due to the strain energy. Under Lewis acid catalysis, 3-alkyloxycyclobutanones can form zwitterionic intermedi-ates and participate in a series of cycloaddition reactions as three-or four-carbon synthons. This Focus Review will mainly discuss formal [4+2], [3+2], and [3+3] annulations as well as other types of transformations with 3-alkyloxycyclobutanones.Scheme 1. Synthesis of 3-alkoxycyclobutanones. DIPEA = diisopropylethylamine; TBME = tert-butyl methyl ether.Scheme 2. Synthesis of 2-monoalkyl-or 2-monoaryl-3-ethoxycyclobutanones.Scheme 3. Synthesis of disubstituted 3-alkoxycyclobutanones.[a] G. Scheme 4. Matsuo's unexpected discovery. LA = Lewis acid. Scheme 9. A practical example for the utility of the alkyne-cobalt complex. Scheme 10. Asymmetric cycloaddition of chiral cyclobutanones. Scheme 11. CÀC insertion of silanes into cyclobutanones. Tf = trifluoromethanesulfonyl. Scheme 12. Possible mechanism for 1,5-hydride transfer. TBDPS = tert-butyldiphenylsilyl. Scheme 13. CÀC bond insertion of silylenol ethers into cyclobutanones. Scheme 14. CÀN insertion into 3-ethoxycyclobutanones. Scheme 15. Application of CÀN insertion into 3-ethoxycyclobutanones in natural product synthesis. DME = 1,2-dimethoxyethane. Scheme 16. Intramolecular cycloaddition of 3-ethoxycyclobutanones. Scheme 17. [3+2] cycloaddition reaction to give pyrazoles. Bz = benzoyl; Cbz = carboyxbenzyl. Scheme 22. Synthesis of unsymmetrical and symmetrical 1,10-phenanthrolines. Scheme 23. Synthesis of b-enamino ketones. Fmoc = 9-fluorenylmethoxycarbonyl.

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“…In 2012, Matsuo and coworkers also reported the use of cobalt octacarbonyl alkyne complexes as donor on cyclobutanones. [217] Scheme 7.35: Formal [4+2] cycloaddition of 3-oxo-cyclobutanones.…”

Section: Reactions With Cyclobutanesmentioning

confidence: 99%

Synthesis of Saturated Heterocycles via Metal-Catalyzed Formal Cycloaddition Reactions That Generate a C–N or C–O Bond

Waser

2013

Topics in Heterocyclic Chemistry

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In this section, the synthesis of saturated N-and O-heterocycles via formal cycloaddition is presented. The main focus is on metal-catalyzed reactions involving C-C or C-X  bond cleavage in three-or four-membered rings. After a fast presentation of pioneering works, the important breakthroughs of the last two decades are presented. The section starts with reactions involving three-membered rings. Formal [3+2] cycloadditions of donor-acceptor-substituted cyclopropanes and methylenecyclopropanes with carbonyls and imines are important methods to access tetrahydrofuran and pyrrolidine heterocycles. Formal [3+3] cycloadditions have emerged more recently. On the other hand, reactions of epoxides and aziridines with carbon monoxide or cumulenes are now well-established method to access heterocycles. These processes have been completed more recently with cycloaddition with olefins, carbonyls and imines. The section ends with the emerging field of four-membered ring activation for cycloaddition with  systems. This is the peer reviewed version of the following article: Top. Heterocycl. Chem. 2013, 32, 225, which The discovery of classical cycloaddition reactions, such as the (hetero) DielsAlder and 1,3-dipolar cycloadditions, has contributed tremendously to a more efficient access towards both carbocycles and heterocycles. The introduction of the term cycloaddition was necessary to distinguish these new types of reactions from previously discovered processes leading to cyclic structures, such as the famous Robinson annulation. In principle, each cycloaddition can be considered as a special case of the more general annulation process, but from which point on an annulation can be called a cycloaddition has been the topic of intensive discussions for decades, and is still not settled today. In 1968, Huisgen proposed a set of rules for the definition of cycloaddition, and the two first are still largely recognized as prerequisite: Although the rule that all the atoms of the starting materials have to be included in the product is not explicitly included in the definition, this requirement is usually recognized by most organic chemists. Even if electrocyclic cyclization processes were included in the original definition of Huisgen, the term cycloaddition is mostly used today for those reactions proceeding via the formation of at least two new bonds. Nevertheless, several researchers think that the term cycloaddition should be more strictly limited to reactions involving a continuous overlap of  electrons, and consequently allowing a concerted process. In fact, in his seminal publication, Huisgen already introduced further rules, in particular rule number 3, which explicitly stated that cycloadditions should not involve the cleavage of sigma bonds: -Huisgen Rule 3: "Cycloadditions do not involve the cleavage of  bonds." Unfortunately, in the same publication, Huisgen also described several reactions proceeding via -bond cleavage as cycloaddition. To solve this definition dilemma, several researchers have used th...

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Formal [4+2] cycloaddition of cyclobutanones bearing alkyne–cobalt complex at their 3-positions

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Cited by 13 publications

References 17 publications

Cobalt-Catalysed Bond Formation Reactions; Part 2

Cobalt-Catalysed Bond Formation Reactions; Part 2

3‐Alkyloxycyclobutanones as Useful Synthons for Heterocycle and Carbocycle Synthesis

Synthesis of Saturated Heterocycles via Metal-Catalyzed Formal Cycloaddition Reactions That Generate a C–N or C–O Bond

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