Free-Radical Reactions of Iodobenzene Dichloride with Hydrocarbons

Banks, David F.; Huyser, Earl S.; Kleinberg, Jacob

doi:10.1021/jo01035a504

Cited by 48 publications

(17 citation statements)

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“…159,171, 161 In possible support of the latter scenario, Ph(Cl)I· (as opposed to Cl·) is thought to be a competent hydrogen-abstractor in photoinitiated C–H chlorinations of hydrocarbons with PhICl 2 , based on comparison of product distributions to similar reactions with Cl 2 . 162 A related question has arisen in ionic mechanisms with PhICl 2 as to whether Cl − or Ph(Cl)I − is the active nucleophile ( vide infra ). 115,159,163 …”

Section: Alkene Dihalogenations With Main Group Halides As Reagentmentioning

confidence: 99%

“…[159,171,161] In possible support of the latter scenario, Ph(Cl)IC (as opposed to ClC)i st hought to be ac ompetent hydrogen-abstractor in photoinitiated CÀHc hlorinations of hydrocarbons with PhICl 2 ,b ased on comparison of product distributions to similar reactions with Cl 2 . [162] Ar elated question has arisen in ionic mechanisms with PhICl 2 as to whether Cl À or Ph(Cl)I À is the active nucleophile (see above). [115,159,163] Regarding the stereochemical course of these radical dichlorinations,m ixtures of anti-a nd syn-dichlorination products are frequently obtained, which for cyclic alkenes typically (though not always) favor the anti-diastereomer.…”

Section: Iodinementioning

confidence: 99%

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Catalytic, Stereoselective Dihalogenation of Alkenes: Challenges and Opportunities

2015

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Although recent years have witnessed significant advances in the development of catalytic, enantioselective halofunctionalizations of alkenes, the related dihalogenation of olefins to afford enantioenriched vicinal dihalide products remains comparatively underdeveloped. However, the growing number of complex natural products bearing halogen atoms at stereogenic centers has underscored this critical gap in the synthetic chemist's arsenal. This Review highlights the selectivity challenges inherent in the design of enantioselective dihalogenation processes, and formulates a mechanism-based classification of alkene dihalogenations, including those that may circumvent the "classical" haliranium (or alkene-dihalogen π-complex) intermediates. A variety of metal and main group halide reagents that have been used for the dichlorination or dibromination of alkenes are discussed, and the proposed mechanisms of these transformations are critically evaluated. AbstractCatalysis of alkene dihalogenation , under different activation modes, with control over both the absolute and relative stereochemical course of dihalogen addition, is one of the most vexing problems in stereoselective synthesis. Dihalogenations that circumvent the "classical" haliranium (or alkene-dihalogen π complex) intermediates provide new and exciting opportunities for catalysis, potentially having broader implications for the design of stereoselective alkene difunctionalizations.

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Section: Alkene Dihalogenations With Main Group Halides As Reagentmentioning

confidence: 99%

Section: Iodinementioning

confidence: 99%

Catalytic, Stereoselective Dihalogenation of Alkenes: Challenges and Opportunities

2015

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“…With either of these reagents, the third propagation step in Scheme 1 would also be facile based on known reactions and reported bond strengths. 8, 9 The work described below focused arbitrarily on the use of CBr 4 as an additive to the remote radical reaction rather than CBrCl 3 .…”

Section: Remote Brominationmentioning

confidence: 99%

Remote functionalization by tandem radical chain reactions

Wiedenfeld¹

1997

J. Chem. Soc., Perkin Trans. 1

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Normal radical relay chlorination of cholestan-3 -ol directed by an attached m-iodobenzoate ester group affords a 9 -chloro steroid, but when the same reaction is conducted in the presence of an excess of CBr 4 the product is a 9 -bromo steroid. Similarly, when the same radical relay reaction is carried out in the presence of an excess of (SCN) 2 rather than CBr 4 , the product is a 9 -thiocyano steroid. Several other examples of these reactions have been developed. These tandem remote functionalization reactions succeed because an intramolecular hydrogen abstraction by a complexed-chlorine atom generates a specific substrate radical in each case.Some years ago the remote radical chlorination of steroids and of linear alkanols directed by attached templates was described. 1 These template-directed reactions differed from those of the traditional synthetic style as geometric constraints, rather than just intrinsic chemical reactivity, were a dominant factor in product formation. Furthermore, without template control a low yield of a complex product mixture would have resulted in each case. The novel steroid products were also of potential medicinal interest and would be difficult to prepare by the traditional synthetic approach. Therefore, it was of interest to generalize the remote chlorination chemistry to other functional groups. Recently the extension of this chemistry to the formation of carbon-bromine and carbon-sulfur bonds by tandem radical chain reactions on one substrate was communicated. 2 This report describes how general the latter reactions were with more of the previously developed 1 radical relay systems. Results and discussionA general strategy for introducing remote functional groups other than chlorine has been developed (Scheme 1). The template-complexed chlorine atom would be produced as in normal remote radical chlorination chemistry. In the first radical chain propagation step, an intramolecular HCl elimination reaction would take place. In the second step, an additive X᎐Y (X,Y ≠ Cl) would react with the substrate radical to give the functionalized product as well as a free radical that was capable of propagating the chain reaction. Implicit in this strategy was the necessity to identify additives which reacted with the substrate radical at a rate similar to that at which the chlorine sources did. This strategy towards remote functionalization was of the tandem type; one reagent was responsible for substrate radical formation, while a second was responsible for the substrate radical functionalization.The initial substrate chosen to test the tandem strategy was Scheme 1cholestan-3α-yl m-iodobenzoate 1 (Scheme 2). This ester was reported to afford 9α-chloride 2 upon reaction with phenyliodine dichloride (PID) under radical relay conditions (Scheme 3). 3 Chloride 2 was found to be a robust material at room temperature and treatment with base or Ag + was necessary to effect elimination. 3 The initial additive tried in the tandem scheme was Br 2 , since this material has long been known to react...

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“…The other involves the use of fluorous iodine(III) dichlorides for free radical chlorinations [ 25 ]. In this regard, phenyl iodine(III) dichloride (PhICl 2 ) is an effective free radical chlorinating agent for hydrocarbons [ 26 – 27 ]. Importantly, the mechanism does not involve the liberation of Cl 2 , followed by the textbook sequence of steps.…”

Section: Introductionmentioning

confidence: 99%

“…Importantly, the mechanism does not involve the liberation of Cl 2 , followed by the textbook sequence of steps. Rather, hydrogen abstraction is effected by a species other than the chlorine radical Cl·, presumably PhICl· [ 26 – 27 ].…”

Section: Introductionmentioning

confidence: 99%

Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds: the role of iodine Lewis basicity

Mukherjee

Biswas

Ehnbom

et al. 2017

Beilstein J. Org. Chem.

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The title molecules are sought in connection with various synthetic applications. The aliphatic fluorous alcohols Rf nCH2OH (Rf n = CF3(CF2)n –1; n = 11, 13, 15) are converted to the triflates Rf nCH2OTf (Tf2O, pyridine; 22–61%) and then to Rf nCH2I (NaI, acetone; 58–69%). Subsequent reactions with NaOCl/HCl give iodine(III) dichlorides Rf nCH2ICl2 (n = 11, 13; 33–81%), which slowly evolve Cl2. The ethereal fluorous alcohols CF3CF2CF2O(CF(CF3)CF2O)xCF(CF3)CH2OH (x = 2–5) are similarly converted to triflates and then to iodides, but efforts to generate the corresponding dichlorides fail. Substrates lacking a methylene group, Rf nI, are also inert, but additions of TMSCl to bis(trifluoroacetates) Rf nI(OCOCF3)2 appear to generate Rf nICl2, which rapidly evolve Cl2. The aromatic fluorous iodides 1,3-Rf6C6H4I, 1,4-Rf6C6H4I, and 1,3-Rf10C6H4I are prepared from the corresponding diiodides, copper, and Rf nI (110–130 °C, 50–60%), and afford quite stable Rf nC6H4ICl2 species upon reaction with NaOCl/HCl (80–89%). Iodinations of 1,3-(Rf6)2C6H4 and 1,3-(Rf8CH2CH2)2C6H4 (NIS or I2/H5IO6) give 1,3,5-(Rf6)2C6H3I and 1,2,4-(Rf8CH2CH2)2C6H3I (77–93%). The former, the crystal structure of which is determined, reacts with Cl2 to give a 75:25 ArICl2/ArI mixture, but partial Cl2 evolution occurs upon work-up. The latter gives the easily isolated dichloride 1,2,4-(Rf8CH2CH2)2C6H3ICl2 (89%). The relative thermodynamic ease of dichlorination of these and other iodine(I) compounds is probed by DFT calculations.

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Free-Radical Reactions of Iodobenzene Dichloride with Hydrocarbons

Cited by 48 publications

References 0 publications

Catalytic, Stereoselective Dihalogenation of Alkenes: Challenges and Opportunities

Catalytic, Stereoselective Dihalogenation of Alkenes: Challenges and Opportunities

Remote functionalization by tandem radical chain reactions

Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds: the role of iodine Lewis basicity

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