IMDA cycloadditions of 3-alkynyl tethered 2-pyrones for the synthesis of medium-sized macrocycles

Shin, Jeong-Taek; Shin, Seunghoon; Cho, Cheon‐Gyu

doi:10.1016/j.tetlet.2004.05.145

Cited by 25 publications

(9 citation statements)

References 28 publications

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“…Naturally, generalizations about the role of substituents on any Diels-Alder cycloadditions should be treated cautiously. However, it is interesting to note that cycloadditions of 4-aryl-substituted 2(H)-pyran-2-one (23) with electron-rich dienophiles are reported to be problematic 35 whereas cycloadditions of 5-aryl-substituted 2(H)-pyran-2-one (24) with vinylene carbonate proceeds efficiently 36 (Scheme 8). Therefore our study indicates that the lack of reactivity and selectivity in the Diels-Alder reactions of 4-substituted 2(H)-pyran-2-ones could be a general feature of the pyrone cycloaddition methodology and a key disadvantage of it.…”

Section: Computational Results and Discussionmentioning

confidence: 99%

“…22,23 Cycloadditions of 2(H)pyran-2-one itself are not selective. Therefore, these easily prepared 18,20 bromopyrones represented a significant advantage over 2(H)-pyran-2-one with the added bonus that the bromine substituent in cycloadducts could be manipulated 24 and hence expanding the diversity of molecules obtained by this method even further.…”

Section: Introductionmentioning

confidence: 99%

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An Experimental and Computational Investigation of the Diels−Alder Cycloadditions of Halogen-Substituted 2(H)-Pyran-2-ones

2005

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[reaction: see text] Diels-Alder reactions of 3- and 5-halo-subsituted 2(H)-pyran-2-ones with both electron-rich and electron-deficient dienophiles afford stable and readily isolable bridged bicyclic lactone cycloadducts. These cycloadditions proceed with excellent regioselectivity and very good stereoselectivity. In contrast, Diels-Alder reactions of 4-halo-subsituted 2(H)-pyran-2-ones afford cycloadducts which are very prone to loss of bridging CO(2) and the subsequent formation of barrelenes ([2.2.2]cyclooctenes). Furthermore, these cycloadditions proceed with only moderate regio- and stereoselectivity. For both series of the 3- and 5-halo-subsituted 2(H)-pyran-2-ones and 4-halo-subsituted 2(H)-pyran-2-ones, the reactivity patterns do not significantly change between the halogens. The regio- and stereochemical preferences of the cycloadditions of halo-substituted 2(H)-pyran-2-ones are investigated computationally. Calculations were carried out on the transition states leading to the four possible regio- and stereoisomeric cycloadducts by using density functional theory (B3LYP/6-31G). These studies allow prediction of the regio- and stereoselectivity in these reactions which are broadly in line with experimental observations.

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Section: Computational Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Experimental and Computational Investigation of the Diels−Alder Cycloadditions of Halogen-Substituted 2(H)-Pyran-2-ones

2005

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“…Although the reactions were not regio- and stereoselective, affording all four possible stereo- and regioisomeric cycloadducts, this was the only known example of an “ambident” 2-azadiene, i.e., one which is capable of both normal and inverse electron-demand Diels−Alder cycloadditions. Curiously, the only other known ambident dienes are halogenated 2( H )-pyran-2-ones, e.g., 3-bromo-2( H )-pyran-2-one,11a 5-bromo-2( H )-pyran-2-one 2 , 11b,c 5-chloro-2( H )-pyran-2-one 3 , and 3,5-dibromo-2( H )-pyran-2-one . Therefore, it appears that 2( H )-1,4-oxazin-2-ones are 2-azadiene counterparts of the well-investigated 2( H )-pyran-2-one dienes.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Diels−Alder Cycloadditions of 2(H)-1,4-Oxazin-2-ones

et al. 2005

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“…A key feature of our strategy is the expectation that the secondary hydroxyl group (or a protected form) in the enone containing tether in ( S )- 5 would provide a bias for π-facial discrimination in an intramolecular Diels–Alder (IMDA) reaction . Specifically, we believed that endo-selective IMDA reaction of ( S )- 5 would take place preferentially via transition state TS-A, in which the OPG group is pseudo-equatorially positioned, rather than TS-B having the OPG group pseudo-axially disposed (Scheme ).…”

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confidence: 99%

H-Bonding Mediated Asymmetric Intramolecular Diels–Alder Reaction in the Formal Synthesis of (+)-Aplykurodinone-1

Lee

Cho

2018

Org. Lett.

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An asymmetric formal total synthesis of (+)-aplykurodinone-1 was achieved using a route, in which hydrogen bonding serves as a stereochemical control element governing the π-facial selectivity of intramolecular Diels–Alder (IMDA) reaction of an enone tethered 2-pyrone. In the IMDA process, the configuration at a stereogenic, hydroxyl bearing an α-carbon in the enone dienophile is conveyed in a highly effective manner through intramolecular hydrogen bonding with the enone carbonyl oxygen. The tricyclic lactone, generated in this process, was successfully converted to a late stage intermediate in Danishefsky’s synthesis of aplykurodinone-1.

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IMDA cycloadditions of 3-alkynyl tethered 2-pyrones for the synthesis of medium-sized macrocycles

Cited by 25 publications

References 28 publications

An Experimental and Computational Investigation of the Diels−Alder Cycloadditions of Halogen-Substituted 2(H)-Pyran-2-ones

An Experimental and Computational Investigation of the Diels−Alder Cycloadditions of Halogen-Substituted 2(H)-Pyran-2-ones

Investigation of the Diels−Alder Cycloadditions of 2(H)-1,4-Oxazin-2-ones

H-Bonding Mediated Asymmetric Intramolecular Diels–Alder Reaction in the Formal Synthesis of (+)-Aplykurodinone-1

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