Synthesis of 4-oxo-2-azetidineacetic acids by means of radical cyclization of N-vinylic α-bromo amides

Ishibashi, Hiroyuki; Kodama, Kazuya; Kameoka, C.; Kawanami, Hirotaka; Ikeda, Masazumi

doi:10.1016/0040-4020(96)00849-6

Cited by 30 publications

(6 citation statements)

References 22 publications

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“…As with all such rules, exceptions are known, − but few of these are sufficiently rapid to be synthetically useful. Recent work from the laboratories of Ishibashi, − Malacria, Clive, Chatgilialoglu, and Tanaka, however, serves to illustrate the potential of such processes. Also of note is the work of Ingold, and the related precedent from Janzen, , illustrating the very rapid ( k = 2 × 10 8 s -1 at 45 °C) 5-endo-trig cyclization of 2-formylbenzoyl and related radicals.…”

Section: β-(Vinyloxy)alkyl To 4-ketobutyl Rearrangementmentioning

confidence: 99%

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: β-(Vinyloxy)alkyl To 4-ketobutyl Rearrangementmentioning

confidence: 99%

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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“…4). 21,22 In contrast, compounds 15a and 15b afforded the desired β‐lactams 16a 23 and 16b ,24 respectively, in good yields. These results suggested that the degree of stabilization with one phenyl group for the radical intermediate by 4‐ exo‐trig cyclization was insufficient, probably because of free rotation of the phenyl group, and that an additional stabilization group was needed to obtain the desired β‐lactams.…”

Section: ‐Exo Vs 5‐endo Radical Cyclizationsmentioning

confidence: 99%

“…Compound 18a could be converted to a potential intermediate for the synthesis of (±)‐PS‐5 25. Cyclizations of enamides having a chiral auxiliary were applied to asymmetric synthesis of (+)‐PS‐5,21,22,27,28 (+)‐thienamycin22,26,28 and 1‐β‐methylcarbapenem 23…”

Section: ‐Exo Vs 5‐endo Radical Cyclizationsmentioning

confidence: 99%

Controlling the regiochemistry of radical cyclizations

Ishibashi

2006

The Chemical Record

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This review describes the results of our recent studies on the control of the regiochemistry of radical cyclizations. N-vinylic alpha-chloroacetamides generally cyclized in a 5-endo-trig manner to give five-membered lactams, whereas 4-exo-trig cyclization occurred when the cyclized radical intermediates were highly stabilized by an adjacent phenyl or phenylthio group to afford beta-lactams. The 5-exo or 6-exo cyclization of aryl radicals onto the alkenic bond of enamides could be shifted to the corresponding 6-endo or 7-endo mode of cyclization by a positional change of the carbonyl group of enamides. The 6-endo- and 7-endo-selective aryl radical cyclizations were applied to radical cascades for the synthesis of alkaloids such as phenanthroindolizidine, cephalotaxine skeleton, and lennoxamine. The 5-exo-trig cyclization of an alkyl radical onto the alkenyl bond of enamides could also be shifted to the 6-endo mode by a positional change of the carbonyl group of enamides. The 6-endo- selective cyclization was applied to the radical cascade to afford a cylindricine skeleton. Other examples of controlling the regiochemistry of radical cyclizations and their applications to the synthesis of natural products are also discussed.

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“…Ikeda, Ishibashi, and co‐workers were the first to show that a variety of halo‐enamides under free‐radical reducing conditions (Bu 3 SnH) cyclized in a “disfavored” 5 ‐endo‐trig manner to give five‐membered lactams with high degree of efficiency (Scheme ) –. However, some exceptions (α‐bromo amides bearing sulfur and/or aryl substituent(s) at the terminus of the N ‐vinylic bond) where β‐lactams resulted from preferential 4‐ exo‐trig cyclization were also described –…”

Section: Intramolecular α‐Alkylation Of α‐Haloamides: Syntheses Of γ‐mentioning

confidence: 99%

The Fascinating Chemistry of α‐Haloamides

et al. 2020

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The aim of this review is to highlight the rich chemistry of α‐haloamides originally mainly used to discover new C−N, C−O and C−S bond forming reactions, and later widely employed in C−C cross‐coupling reactions with C(sp3), C(sp2) and C(sp) coupling partners. Radical‐mediated transformations of α‐haloamides bearing a suitable located unsaturated bond has proven to be a straightforward alternative to access diverse cyclic compounds by means of either radical initiators, transition metal redox catalysis or visible light photoredox catalysis. On the other hand, cycloadditions with α‐halohydroxamate‐based azaoxyallyl cations have garnered significant attention. Moreover, in view of the important role in life and materials science of difluoroalkylated compounds, a wide range of catalysts has been developed for the efficient incorporation of difluoroacetamido moieties into activated as well as unactivated substrates.

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Synthesis of 4-oxo-2-azetidineacetic acids by means of radical cyclization of N-vinylic α-bromo amides

Cited by 30 publications

References 22 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

Controlling the regiochemistry of radical cyclizations

The Fascinating Chemistry of α‐Haloamides

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