Facile Synthesis of α-Keto Esters via A Free Radical Acylation Approach

Kim, Sunggak; Yoon, Joo‐Yong; Lee, Ill Young

doi:10.1055/s-1997-6143

Cited by 39 publications

(14 citation statements)

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“…No correlation was found with any of the σ • scales examined. The reaction coefficient of 2.1 versus σ p is very high for a radical reaction and strongly supports the notion that the (phosphatoxy)alkyl migration proceeds via transition states with substantial polar character, polarized in the way shown To gain an insight into the extent of polarization of the acyloxy shift, Beckwith and Duggan determined the rates of rearrangement of three p-substituted phenylpropyl butyrate derived radicals (438-440) and the related 441, generated from the corresponding bromides, by means of the stannane clock method ( Table 2, entries [16][17][18][19][20][21][22][23][24]. 164 At 75°C in benzene, a Hammett correlation with the substituent constant σ p + was obtained, giving a reaction coefficient of F ) -0.71.…”

Section: Quantitative Structure Activity Relationshipsmentioning

confidence: 64%

Chemistry of β-(Acyloxy)alkyl and β-(Phosphatoxy)alkyl Radicals and Related Species: Radical and Radical Ionic Migrations and Fragmentations of Carbon−Oxygen Bonds

et al. 1997

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ContentsI. Introduction 3273 II. Rearrangements 3275 A. β-(Acyloxy)alkyl Rearrangement 3275 1. Esters 3275 2. Lactones 3280 3. Thiocarbonyl Esters 3280 B. β-(Phosphatoxy)alkyl Rearrangement 3282 C. β-(Nitroxy)alkyl and β-(Sulfonatoxy)alkyl Rearrangements 3285 D. (Acyloxyalkyl)silyl Radical Rearrangement 3285 III. Fragmentation Reactions 3286 A. β-(Acyloxy)alkyl Radicals and Their Thiocarbonyl Analogues 3286 B. β-(Phosphatoxy)alkyl Radicals 3288 1. Anaerobic Conditions 3288 2. Aerobic Conditions 3293 C. β-(Sulfonatoxy)alkyl and Related Radicals 3294 IV. Mechanism 3294 A. β-(Ester)alkyl Radicals Susceptible to Neither Rearrangement Nor Fragmentation 3294 B. Fragmentation Reactions 3295 C. Rearrangement Reactions 3295 1. Noncage Dissociative Pathways 3296 2. Stepwise Pathways via Five-Membered Cyclic Intermediate Radicals 3296 3. Use of Isotopic and Stereochemical Labeling as Probes of Mechanism 3296 4. Quantitative Structure Activity Relationships 3298 5. Computational Studies and ESR Considerations 3299 V. Overview of β-(Ester)alkyl Radical Reactions 3303 VI. Related Reactions Involving Radical C−O Bond Shift and Cleavage 3305 A. Rearrangement and Fragmentation of β-Hydroxyalkyl Radicals 3305 B. Schenck or Allylperoxy Radical Rearrangement 3307 C. β-(Vinyloxy)alkyl to 4-Ketobutyl Rearrangement 3308 VII. Acknowledgments 3309 VIII. References 3309 Scheme 6

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Section: Quantitative Structure Activity Relationshipsmentioning

confidence: 64%

Chemistry of β-(Acyloxy)alkyl and β-(Phosphatoxy)alkyl Radicals and Related Species: Radical and Radical Ionic Migrations and Fragmentations of Carbon−Oxygen Bonds

et al. 1997

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“…The present approach was further extended to the synthesis of α ‐oxime ester 10 , a synthetic equivalent of an α ‐keto ester, by using ethoxycarbonyl oxime ether 9 [Eq. (4) ] 9. The reaction was carried out under the same conditions and afforded 10 in good yields (64 to 75 %) without formation of 11 (Table 1).…”

Section: Methodsmentioning

confidence: 98%

Tin-Free Radical Acylation Reactions with Methanesulfonyl Oxime Ether

Kim

Song

Choi

et al. 2001

Angew. Chem. Int. Ed.

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A simple strategy involving thermal decomposition of the methanesulfonyl radical into the methyl radical and the subsequent transfer of an iodine atom or phenyl telluride group was used to develop a tin‐free radical acylation reaction (see scheme; V‐40=1,1′‐azobis(cyclohexane‐1‐carbonitrile). The key was finding reaction conditions under which the I or PhTe transfer is faster than the direct addition of the alkyl radical to the methanesulfonyl oxime ether.

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“…Evidently, addition of the ethyl radical to 4 is more than two times faster than the transfer of the iodine atom from cyclohexyl iodide to the ethyl radical. [9] R I N (4) We next turned our attention to methanesulfonyl oxime ether 5.…”

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confidence: 99%

Tin-Free Radical Acylation Reactions with Methanesulfonyl Oxime Ether

et al. 2001

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Recent advances in radical reactions have greatly benefited from the efficiency of organotin reagents as mediators. However, organotin reagents are highly toxic, and it is difficult to remove their residues from the products. These disadvantages have proved to be a serious barrier to industrial applications. To solve the problems associated with toxic organotin reagents, several alternative approaches, including the use of polymer-supported organotin reagents and organosilanes, have been utilized with some success. [1] Recently, a few tin-free carbon ± carbon bond-forming reactions were reported; they include organosulfone-mediated radical allylation, alkenylation, alkynylation, and azidation reactions. [2±4] Recently, we reported highly efficient tin-mediated radical acylation reactions with sulfonyl oxime ethers [Eq. ( 1)]. [5] We then studied the possibility of environmentally benign tin-free

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Facile Synthesis of α-Keto Esters via A Free Radical Acylation Approach

Cited by 39 publications

References 0 publications

Chemistry of β-(Acyloxy)alkyl and β-(Phosphatoxy)alkyl Radicals and Related Species: Radical and Radical Ionic Migrations and Fragmentations of Carbon−Oxygen Bonds

Chemistry of β-(Acyloxy)alkyl and β-(Phosphatoxy)alkyl Radicals and Related Species: Radical and Radical Ionic Migrations and Fragmentations of Carbon−Oxygen Bonds

Tin-Free Radical Acylation Reactions with Methanesulfonyl Oxime Ether

Tin-Free Radical Acylation Reactions with Methanesulfonyl Oxime Ether

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