Gold(I)‐ and Brønsted Acid‐Catalyzed Ring‐Opening of Unactivated Vinylcyclopropanes with Sulfonamides

Shi, Wen‐Jian; Liu, Yanyun; Butti, Pietro; Togni, Antonio

doi:10.1002/adsc.200700006

Cited by 52 publications

(26 citation statements)

References 42 publications

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“…Interestingly, this contrasted with a previous study by Togni and co-workers, who had demonstrated one example of a closely related VCP readily undergoing tandem ring-opening/intramolecular hydroamination with TsNH 2 to give the corresponding pyrrolidine adduct in 64 % yield. [12] The likely involvement of a diene intermediate in reactions with secondary alcohols, on the other hand, was supported by our findings when we investigated the cyclization of 1 l in the presence of (p-CF 3 C 6 H 4 ) 3 PAuCl/AgOTf (5 mol %) under the conditions shown in Scheme 2b at shorter reaction times. This revealed the production of the disubstituted trans diene 3 a, structurally determined by Xray crystallography (see Figure S45 in the Supporting Information), along with 4 a (yields of 62 and 30 %, respectively).…”

Section: Resultssupporting

confidence: 64%

Cyclopropyl Carbinol Rearrangement for Benzo‐Fused Nitrogen Ring Synthesis

Kothandaraman

Huang

Susanti

et al. 2011

Chemistry A European J

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A synthetic method that relies on gold-catalysed cyclopropyl carbinol rearrangement of 2-tosylaminophenyl cyclopropylmethanols to prepare 2,3-dihydro-1H-benzo[b]azepines and 2-vinylindolines efficiently is reported. The reactions were shown to be chemoselective, with secondary and tertiary alcohol substrates exclusively providing benzo-fused five- and seven-membered ring products, respectively. The ring-forming process was also found to proceed in moderate to excellent yields under mild conditions only in the presence of the gold and silver catalyst combination. The mechanism is thought to involve activation of the alcohol by the (p-CF(3)C(6)H(4))(3)PAuCl/AgOTf (Tf = triflate) catalyst, resulting in ionization of the starting material. The tertiary carbocationic intermediate generated in situ in this manner then triggers ring-opening of the cyclopropane moiety and trapping by the tethered aniline group to give the 2,3-dihydro-1H-benzo[b]azepine. Cyclopropane ring fragmentation of the secondary carbocationic analogue, on the other hand, results in diene formation followed by subsequent intramolecular hydroamination to afford the 2-vinylindoline.

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Section: Resultssupporting

confidence: 64%

Cyclopropyl Carbinol Rearrangement for Benzo‐Fused Nitrogen Ring Synthesis

Kothandaraman

Huang

Susanti

et al. 2011

Chemistry A European J

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“…A third possible pathway involves the deprotonation of carbonium species II , in which R 3 = CH 2 R 5 , to afford cyclopropane intermediate 12 . Further coordination of the π‐acidic silver(I) catalyst to the C=C bond of this newly formed adduct may then trigger a nucleophilic attack by the pendant hydroxyl group in complex IV on the ring motif 23. This results in the opening of the cyclopropyl ring to form organosilver complex V , which upon protonolysis releases the metal catalyst to afford bicycloadduct 8 .…”

Section: Resultsmentioning

confidence: 99%

On the Oxidation of the Three‐Dimensional Aromatics [B₁₂X₁₂]²⁻ (X=F, Cl, Br, I)

Boeré

Derendorf

Jenne

et al. 2014

Chemistry A European J

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The perhalogenated closo-dodecaborate dianions [B12 X12 ](2-) (X=H, F, Cl, Br, I) are three-dimensional counterparts to the two-dimensional aromatics C6 X6 (X=H, F, Cl, Br, I). Whereas oxidation of the parent compounds [B12 H12 ](2-) and benzene does not lead to isolable radicals, the perhalogenated analogues can be oxidized by chemical or electrochemical methods to give stable radicals. The chemical oxidation of the closo-dodecaborate dianions [B12 X12 ](2-) with the strong oxidizer AsF5 in liquid sulfur dioxide (lSO2 ) yielded the corresponding radical anions [B12 X12 ](⋅-) (X=F, Cl, Br). The presence of radical ions was proven by EPR and UV/Vis spectroscopy and supported by quantum chemical calculations. Use of an excess amount of the oxidizing agent allowed the synthesis of the neutral perhalogenated hypercloso-boranes B12 X12 (X=Cl, Br). These compounds were characterized by single-crystal X-ray diffraction of dark blue B12 Cl12 and [Na(SO2 )6 ][B12 Br12 ]⋅B12 Br12 . Sublimation of the crude reaction products that contained B12 X12 (X=Cl, Br) resulted in pure dark blue B12 Cl12 or decomposition to red B9 Br9 , respectively. The energetics of the oxidation processes in the gas phase were calculated by DFT methods at the PBE0/def2-TZVPP level of theory. They revealed the trend of increasing ionization potentials of the [B12 X12 ](2-) dianions by going from fluorine to bromine as halogen substituent. The oxidation of all [B12 X12 ](2-) dianions was also studied in the gas phase by mass spectrometry in an ion trap. The electrochemical oxidation of the closo-dodecaborate dianions [B12 X12 ](2-) (X=F, Cl, Br, I) by cyclic and Osteryoung square-wave voltammetry in liquid sulfur dioxide or acetonitrile showed very good agreement with quantum chemical calculations in the gas phase. For [B12 X12 ](2-) (X=F, Cl, Br) the first and second oxidation processes are detected. Whereas the first process is quasi-reversible (with oxidation potentials in the range between +1.68 and +2.29 V (lSO2 , versus ferrocene/ferrocenium (Fc(0/+) ))), the second process is irreversible (with oxidation potentials ranging from +2.63 to +2.71 V (lSO2 , versus Fc(0/+) )). [B12 I12 ](2-) showed a complex oxidation behavior in cyclic voltammetry experiments, presumably owing to decomposition of the cluster anion under release of iodide, which also explains the failure to isolate the respective radical by chemical oxidation.

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“…Alkyl and aryl mono-and di-substituted MCPs underwent effective gold(I)-catalyzed ring-opening/ring-closing hydroamination. Likewise, Togni has demonstrated the gold(I)-catalyzed ring-opening hydroamination of vinylcyclopropanes (VCPs) with sulfonamides [58]. For example, reaction of VCP 85 with methylsulfonamide and a catalytic 1 : 1 mixture of (PPh 3 ) AuCl and AgOTf in toluene at 50 C for 24 h led to isolation of 4-phenyl-3-pentenyl sulfonamide 86 in 97% yield (Eq.…”

Section: Ammonium Salts As Nucleophilesmentioning

confidence: 99%

“…(11.48)). It should also be noted that compound 86 was isolated in 92% yield from reaction of 85 and methylsulfonamide catalyzed by HOTf at 50 C for 24 h [58]. 85 He has reported the gold(I)-catalyzed intermolecular hydroamination of 1,3-dienes with carbamates and sulfonamides to form allylic amines [59].…”

Section: Ammonium Salts As Nucleophilesmentioning

confidence: 99%