Generation of Acyl Radicals from Thiolesters by Intramolecular Homolytic Substitution at Sulfur

Crich, David; Yao, Qingwei

doi:10.1021/jo960115e

Cited by 88 publications

(46 citation statements)

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“…26 On treatment with tributylstannane and a radical initiator, acyl selenides 27,28 provide convenient sources of acyl radicals, 29 as do certain classes of acyl sulfide. [30][31][32] Alternatively, acyl tellurides 33 and acylcobalt(III) 34 derivatives can provide acyl radicals on white light photolysis. Qingwei Yao was born in northern Shanxi, Peoples Republic of China, in 1963 and received his college education at Shanxi Medical College (1979− 1983).…”

Section: Introductionmentioning

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: Introductionmentioning

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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“…[10,11] Sulfur is particularly wellsuited, and several reactions have been reported that employ homolytic substitution on this particular atom. A variety of different functions have been introduced (sulfides, [12][13][14] disulfides, [15] thioesters, [16][17][18] and sulfoxides; [14,19,20] sulfones seem not to be prone to such processes [14,21] ), but so far none in which an additional heteroatom was present in the ring next to the sulfur atom, despite the increased potential offered by the heterocyclic adducts.…”

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Formation of Cyclic Sulfinates and Sulfinamides through Homolytic Substitution at the Sulfur Atom

et al. 2006

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Ring road: Cyclic sulfinates and sulfinamides can be synthesized by homolytic substitution to give alkyl and benzofused families of compounds. The presence of an additional heteroatom in the ring allows the preparation of sulfur‐based heterocycles that are useful synthetic intermediates (see scheme). The stereogenic sulfur atom transfers its chirality to prochiral radicals. TTMSS=tris(trimethylsilyl)silane, AIBN=azobisisobutyronitrile.

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“…Dubbed polarityreversal catalysis by Roberts, the success of this chemistry, has been attributed to favorable polar effects in the transition state for H-atom transfer from an S-to a C-centered radical (e.g., 5) over the less favorable transition state (e.g., 6) and has been supported by computational-chemistry techniques [7]. A similar catalytic phenomenon has been described by Crich and co-workers for reactions involving stannanes catalyzed by benzeneselenol, a technique that effectively extends the kinetic range of stannane-mediated reactions [8]. It is interesting to note that Roberts showed that alkenes could be easily hydrosilylated by using silane/thiol mixtures [9].…”

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confidence: 70%

“…-We began this study by examining the reaction of a-{[(tert-butyl)dimethylsilyl]oxy}styrene (1) with tributylstannane (2c) at 808 in the absence of solvent (AIBN initiator). Benzeneselenol (PhSeH) was generated by the in situ method described by Crich and co-workers [8], that is by the rapid ionic reaction of diphenyl diselenide with 2c (Scheme 3). The outcomes of this initial investigation are listed in Table 1.…”

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Polarity‐Reversal‐Catalyzed Hydrostannylation Reactions: Benzeneselenol‐Mediated Homolytic Hydrostannylation of Electron‐Rich Olefins

Ford

Wille

Schiesser

2006

Helvetica Chimica Acta

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Dedicated to the memory of Professor Hanns Fischer. We take for granted his many contributions to the field of radical chemistry. I am particularly indebted to his careful and patient explaining to me of the persistent radical effect over a drink, on a balmy New Hampshire evening.Addition of 10 mol-% of diphenyl diselenide to hydrostannylation reactions involving electron-rich olefins results in a dramatic improvement in yield. For example, reaction of a-{[(tert-butyl)dimethylsilyl]-A C H T U N G T R E N N U N G oxy}styrene (1) with triphenylstannane (2a; 1.1 equiv.) in the presence of PhSeSePh and 2,2'-azobis[2-methylpropanenitrile] (AIBN) affords {2-{[(tert-butyl)dimethylsilyl]oxy}-2-phenylethyl}triphenylstan-nane (3a) in 95% yield after 2 h. This reaction presumably benefits, by the increased rate of H-atom transfer, from the in situ generated polarity-reversal catalyst, benzeneselenol.

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Generation of Acyl Radicals from Thiolesters by Intramolecular Homolytic Substitution at Sulfur

Cited by 88 publications

References 47 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

Formation of Cyclic Sulfinates and Sulfinamides through Homolytic Substitution at the Sulfur Atom

Polarity‐Reversal‐Catalyzed Hydrostannylation Reactions: Benzeneselenol‐Mediated Homolytic Hydrostannylation of Electron‐Rich Olefins

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