Kinetics and mechanism for the formation of o‐carboxy(N‐methyl)‐benzohydroxamic acid in the cleavage of ethyl N‐[o‐(N‐methyl‐N‐hydroxycarbamoyl)‐benzoyl]carbamate in N‐methylhydroxylamine,acetate, and phosphate buffers

The rate of cleavage of ethyl N‐[o‐(N‐methyl‐N‐hydroxycarbamoyl)benzoyl]‐ carbamate (ENMBC) in the buffer solutions containing N‐methylhydroxylamine, acetate + N‐methylhydroxylamine, and phosphate + N‐methylhydroxylamine followed an irreversible consecutive reaction path: ENMBC where A and B represent N‐hydroxyl group cyclized product of ENMBC and o‐(N‐methyl‐N‐hydroxycarbamoyl)benzoic acid, respectively. Both rate constants k_{1 obs} and k_{2 obs} showed the presence of buffer catalysis, but buffer catalysis turned out to be weak in the presence N‐methylhydroxylamine buffer, while it was strong in the presence of acetate and phosphate ones. Buffer‐independent rate constants k₁₀ and k₂₀ increased linearly with the increase in a_OH with definite intercepts. The values of molar absorption coefficient of A , obtained under varying total buffer concentrations at a constant pH, showed the presence of a fast equilibrium: A + CH₃NHOH ? C , where C represents N‐[o‐(N‐methyl‐N‐hydroxycarbamoyl)methyl]benzohydroxamic acid. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 427–437, 2003     

Cobalt‐Catalyzed Electrophilic Amination of Aryl‐ and Heteroarylzinc Pivalates with N‐Hydroxylamine Benzoates

Aryl‐ and heteroarylzinc pivalates can be aminated with O‐benzoylhydroxylamines at 25 °C within 2–4 h in the presence of 2.5–5.0 % CoCl₂?2 LiCl to furnish the corresponding tertiary arylated or heteroarylated amines in good yields. This electrophilic amination also provides access to diarylamines and aryl(heteroaryl)amines. A new tuberculosis drug candidate (Q203) was prepared in six steps and 56 % overall yield by using this cobalt‐catalyzed amination as the key step.     

Influence of the stereochemical configuration on the radical polymerization of methacrylic monomers: cis‐ and trans‐(2‐cyclohexyl‐1,3‐dioxan‐5‐yl) methacrylate

The synthesis of two new isomeric monomers, cis‐(2‐cyclohexyl‐1,3‐dioxan‐5‐yl) methacrylate (CCDM) and trans‐(2‐cyclohexyl‐1,3‐dioxan‐5‐yl) methacrylate (TCDM), starting from the reaction of glycerol and cyclohexanecarbaldehyde, is reported. The process involved the preparation of different alcohol acetals and esterification with methacryloyl chloride of the corresponding cis and trans 5‐hydroxy compounds of 2‐cyclohexyl‐1,3‐dioxane. The radical polymerization reactions of both monomers, under the same conditions of temperature, solvent, monomer, and initiator concentrations, were studied to investigate the influence of the monomer configuration on the values of the propagation and termination rate constants (k_p and k_t ).The values of the ratio k_p /k_t ^1/2 were determined by UV spectroscopy by the measurement of the changes of absorbance with time at several wavelengths in the range 275–285 nm, where an appropriate change in absorbance was observed. Reliable values of the kinetics constants were determined by UV spectroscopy, showing a very good reproducibility of the kinetic experiments. The values of k_p /k_t ^1/2, in the temperature interval 45–65 °C, lay in the range 0.40–0.50 L^1/2/mol^1/2s^1/2 and 0.20–0.30 L^1/2/mol^1/2s^1/2 for CCDM and TCDM, respectively. Measurements of both the radical concentrations and the absolute rate constants k_p and k_t were also carried out with electron paramagnetic resonance techniques. The values of k_p at 60 °C were nearly identical for both the trans and cis monomers, but the termination rate constant of the trans monomer was about three times that of the cis monomer at the same temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3883–3891, 2000     

Kinetic and ESR studies on the radical polymerization of α‐n‐(α′‐methylbenzyl) β‐ethyl itaconamates derived from racemic and (s)‐α‐methylbenzylamines

The polymerization of α‐N‐(α′‐methylbenzyl) β‐ethyl itaconamate derived from racemic α‐methylbenzylamine (RS‐MBEI) by initiation with dimethyl 2,2′‐azobisisobutyrate (MAIB) was studied in methanol kinetically and with ESR spectroscopy. The overall activation energy of polymerization was calculated to be 47 kJ/mol, a very low value. The polymerization rate (R_p ) at 60 °C was expressed by R_p = k[MAIB]^0.5±0.05[RS‐MBEI]^2.9±0.1. The rate constants of propagation (k_p ) and termination (k_t ) were determined by ESR. k_p was very low, ranging from 0.3 to 0.8 L/mol s, and increased with the monomer concentration, whereas k_t (4–17 × l0⁴ L/mol s) decreased with the monomer concentration. Such behaviors of k_p and k_t were responsible for the high dependence of R_p on the monomer concentration. R_p depended considerably on the solvent used. S‐MBEI, derived from (S)‐α‐methylbenzylamine, showed somewhat lower homopolymerizability than RS‐MBEI. The k_p value of RS‐MBEI at 60 °C in benzene was 1.5 times that of S‐MBEI. This was explicable in terms of the different molecular associations of RS‐MBEI and S‐MBEI, as analyzed by ¹H NMR. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4137–4146, 2000     

Mechanism and kinetics of the imidazolidinone nitroxide‐mediated free‐radical polymerization of styrene

Styrene radical polymerizations mediated by the imidazolidinone nitroxides 2,5‐bis(spirocyclohexyl)‐3‐methylimidazolidin‐4‐one‐1‐oxyl (NO88Me) and 2,5‐bis(spirocyclohexyl)‐3‐benzylimidazolidin‐4‐one‐1‐oxyl (NO88Bn) were investigated. Polymeric alkoxyamine (PS‐NO88Bn)‐initiated systems exhibited controlled/living characteristics at 100–120 °C but not at 80 °C. All systems exhibited rates of polymerization similar to those of thermal polymerization, with the exception of the PS‐NO88Bn system at 80 °C, which polymerized twice as quickly. The dissociation rate constants (k_d) for the PS‐NO88Me and PS‐NO88Bn coupling products were determined by electron spin resonance at 50–100 °C. The equilibrium constants were estimated to be 9.01 × 10^?11 and 6.47 × 10^?11 mol L^?1 at 120 °C for NO88Me and NO88Bn, respectively, resulting in the combination rate constants (k_c) 2.77 × 10⁶ (NO88Me) and 2.07 × 10⁶ L mol^?1 s^?1 (NO88Bn). The similar polymerization results and kinetic parameters for NO88Me and NO88Bn indicated the absence of any 3‐N‐transannular effect by the benzyl substituent relative to the methyl substituent. The values of k_d and k_c were 4–8 and 25–33 times lower, respectively, than the reported values for PS‐TEMPO at 120 °C, indicating that the 2,5‐spirodicyclohexyl rings have a more profound effect on the combination reaction rather than the dissociation reaction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 327–334, 2003     

Elementary reaction analysis of the radical polymerization of α‐ethyl β‐N‐(α′‐methylbenzyl)itaconamates carrying (RS)‐ and (S)‐α‐methylbenzylaminocarbonyl groups

The polymerizations of α‐ethyl β‐N‐(α′‐methylbenzyl)itaconamates carrying (RS)‐ and (S)‐α‐methylbenzylaminocarbonyl groups (RS‐EMBI and S‐EMBI) with dimethyl 2,2′‐azobisisobutyrate (MAIB) were studied in methanol (MeOH) and in benzene kinetically and with electron spin resonance (ESR) spectroscopy. The initial polymerization rate (R_p) at 60 °C was given by R_p = k[MAIB]^{0.58 ± 0.05}[RS‐EMBI]^{2.4 ± 0.l} and R_p = k[MAIB]^{0.61 ± 0.05}[S‐EMBI]^{2.3 ± 0.l} in MeOH and R_p = k[MAIB]^{0.54 ± 0.05}[RS‐EMBI]^{1.7 ± 0.l} in benzene. The rate constants of initiation (k_df), propagation (k_p), and termination (k_t) as elementary reactions were estimated by ESR, where k_d is the rate constant of MAIB decomposition and f is the initiator efficiency. The k_p values of RS‐EMBI (0.50–1.27 L/mol s) and S‐EMBI (0.42–1.32 L/mol s) in MeOH increased with increasing monomer concentrations, whereas the k_t values (0.20?7.78 × 10⁵ L/mol s for RS‐EMBI and 0.18?6.27 × 10⁵ L/mol s for S‐EMBI) decreased with increasing monomer concentrations. Such relations of R_p with k_p and k_t were responsible for the unusually high dependence of R_p on the monomer concentration. The activation energies of the elementary reactions were also determined from the values of k_df, k_p, and k_t at different temperatures. R_p and k_p of RS‐EMBI and S‐EMBI in benzene were considerably higher than those in MeOH. R_p of RS‐EMBI was somewhat higher than that of S‐EMBI in both MeOH and benzene. Such effects of the kinds of solvents and monomers on R_p were explicable in terms of the different monomer associations, as analyzed by ¹H NMR. The copolymerization of RS‐EMBI with styrene was examined at 60 °C in benzene. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1819–1830, 2003     

Incubation period in the 2,2,4,4‐tetramethyl‐1‐piperidinyloxy‐mediated thermal autopolymerization of styrene: Kinetics and simulations

Mechanisms and simulations of the induction period and the initial polymerization stages in the nitroxide‐mediated autopolymerization of styrene are discussed. At 120–125 °C and moderate 2,2,4,4‐tetramethyl‐1‐piperidinyloxy (TEMPO) concentrations (0.02–0.08 M), the main source of radicals is the hydrogen abstraction of the Mayo dimer by TEMPO [with the kinetic constant of hydrogen abstraction (k_h)]. At higher TEMPO concentrations ([N?] > 0.1 M), this reaction is still dominant, but radical generation by the direct attack against styrene by TEMPO, with kinetic constant of addition k_ad, also becomes relevant. From previous experimental data and simulations, initial estimates of k_h ≈ 1 and k_ad ≈ 6 × 10^?7 L mol^?1 s^?1 are obtained at 125 °C. From the induction period to the polymerization regime, there is an abrupt change in the dominant mechanism generating radicals because of the sudden decrease in the nitroxide radicals. Under induction‐period conditions, the simulations confirm the validity of the quasi‐steady‐state assumption (QSSA) for the Mayo dimer in this regime; however, after the induction period, the QSSA for the dimer is not valid, and this brings into question the scientific basis of the well‐known expression k_th[M]³ (where [M] is the monomer concentration and k_th is the kinetic constant of autoinitiation) for the autoinitiation rate in styrene polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6962‐6979, 2006     

Radical‐initiated polymerization of β‐methyl‐α‐methylene‐γ‐butyrolactone

β‐Methyl‐α‐methylene‐γ‐butyrolactone (MMBL) was synthesized and then was polymerized in an N,N‐dimethylformamide (DMF) solution with 2,2‐azobisisobutyronitrile (AIBN) initiation. The homopolymer of MMBL was soluble in DMF and acetonitrile. MMBL was homopolymerized without competing depolymerization from 50 to 70 °C. The rate of polymerization (R_p) for MMBL followed the kinetic expression R_p = [AIBN]^0.54[MMBL]^1.04. The overall activation energy was calculated to be 86.9 kJ/mol, k_p/k_t^1/2 was equal to 0.050 (where k_p is the rate constant for propagation and k_t is the rate constant for termination), and the rate of initiation was 2.17 × 10^?8 mol L^?1 s^?1. The free energy of activation, the activation enthalpy, and the activation entropy were 106.0, 84.1, and 0.0658 kJ mol^?1, respectively, for homopolymerization. The initiation efficiency was approximately 1. Styrene and MMBL were copolymerized in DMF solutions at 60 °C with AIBN as the initiator. The reactivity ratios (r₁ = 0.22 and r₂ = 0.73) for this copolymerization were calculated with the Kelen–Tudos method. The general reactivity parameter Q and the polarity parameter e for MMBL were calculated to be 1.54 and 0.55, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1759–1777, 2003     

Visible‐Light‐Induced Trifluoromethylation of Isonitrile‐Substituted Methylenecyclopropanes: Facile Access to 6‐(Trifluoromethyl)‐7,8‐Dihydrobenzo[k]phenanthridine Derivatives

A new visible‐light‐induced trifluoromethylation of isonitrile‐substituted methylenecyclopropanes is developed. A range of substituted 6‐(trifluoromethyl)‐7,8‐dihydrobenzo[k]phenanthridine derivatives are readily furnished by this newly developed tandem reaction with moderate to good yields. This reaction allows the direct formation of two six‐membered rings and three new C?C bonds, including the C?CF₃ bond, under visible light irradiation.     

Kinetics of the polycondensation and copolycondensation of bis(3‐hydroxypropyl) terephthalate and bis(4‐hydroxybutyl) terephthalate

The kinetics of the polycondensation and copolycondensation reactions of bis(3‐hydroxypropyl) terephthalate (BHPT) and bis(4‐hydroxybutyl) terephthalate (BHBT) as monomers were investigated at 270 °C in the presence of titanium tetrabutoxide as a catalyst. BHPT was prepared by the ester interchange reaction of dimethyl terephthalate and 1,3‐propanediol (1,3‐PD). Through the same method adopted for BHPT synthesis, BHBT was prepared with 1,4‐butanediol instead of 1,3‐PD. With second‐order kinetics applied for polycondensation, the rate constants of the polycondensation of BHPT and BHBT, k₁₁ and k₂₂, were calculated to be 4.08 and 4.18 min^?1, respectively. The rate constants of the cross reactions in the copolycondensation of BHPT and BHBT, k₁₂ and k₂₁, were calculated with results obtained from proton nuclear magnetic resonance spectroscopy analysis. The rate constants during the copolycondensation of BHPT and BHBT at 270 °C decreased in the order k₁₂ > k₂₂ > k₁₁ > k₂₁, indicating that the reactivity of BHBT was larger than that of BHPT at 270 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2435–2441, 2002     

Solvent and Substituent Effects in the Solvolysis of 9‐Aryl‐9‐bromofluorenes

The solvolysis of eight 9‐aryl‐9‐bromofluorenes ( 6b～6i ) in a variety of solvents were studied. Correlation analysis using single‐parameter Grunwald‐Winstein equation (Eqn. 1) with different Y scales showed good linearity (R ≥ 0.98) for most cases if Y_xBnBr was employed. Linear relationships were observed from Hammett‐type analysis of logarithm of rate constants using Brown‐Okamoto σ⁺ constants (Eqn. 3), although inverse order of k(p‐CF₃)/k(m‐ CF₃) was realized in a number of cases. The ρ values were found to vary slightly with different solvent systems. Calculated atomic charge reveals the similarity between 9‐phenyl‐9‐fluorenyl cation ( 7 ) and triphenylmethyl cation ( 8 ). An extended charge delocalization throughout the fluorenyl ring led to the conclusion of the insignificance of antiaromaticity, which was in harmony with that obtained in previous studies. The variation of relative k_Br/k_Cl rate ratios was attributed to the electrophilic pull by solvents in solvolysis.     

Synthesis of a series of SG1 2‐[N‐tert‐butyl‐N‐(1‐diethoxyphosphoryl‐2,2‐dimethylpropyl)aminoxyl] based alkoxyamines,SG1‐CH(Me)CO2R,and measurement of the homolysis rate constants of the C?ON bond

During nitroxide‐mediated polymerization, the polymerization time decreases with an increasing rate constant of the cleavage of the NO? C bond of dormant alkoxyamines. Thus, knowledge of the factors influencing this cleavage is of considerable interest. We have prepared a series of SG1 2‐[N‐tert‐butyl‐N‐(1‐diethoxyphosphoryl‐2,2‐dimethylpropyl)aminoxyl] based alkoxyamines [SG1‐CH(Me)CO₂R] with various R groups (alkyl or aryl) and measured the homolysis rate constants (k_d). k_d decreases with the bulkiness and increases with the polarity of the R group. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3504–3515, 2004     

1,3‐Dipolar Cycloaddition of Diazo Compounds to Electron‐Deficient Alkenes: Kinetics and Mechanism of Formation of Dimethyl‐4,5‐dihydro‐1H‐pyrazol‐3,5‐dicarboxylate

1,3‐Dipolar cycloaddition of methyl diazoacetate to methyl acrylate was investigated by kinetic ¹Н NMR spectroscopy. It was established that the mechanism of the process includes parallel formation of trans‐ and cis‐dimethyl‐4,5‐dihydro‐3H‐pyrazol‐3,5‐dicarboxylates as a result of [3 + 2]‐cycloaddition of methyl diazoacetate to methyl acrylate; the corresponding rate constants were denoted k_1t and k_1c. The reaction rate of the isomerization of 3Н‐pyrazolines to 4,5‐dihydro‐1H‐pyrazol‐3,5‐dicarboxylate (3Н → 1Н‐pyrazoline rearrangement) was found to be sensitive to both the methyl acrylate (k_2t, k_2c) and 1Н‐pyrazoline concentrations (k_3t, k_3c). Kinetic analysis showed that the proposed scheme is valid for various reagent concentrations. The numerical solution of the system of differential equations corresponded to the reaction scheme and was used to determine the complete set of reaction rate constants (k (× 10⁵ M^–1·s^–1), 298 K; solvent, benzene‐d₆): k_1t = 2.3 ± 0.3, k_1c = 1.6 ± 0.2, k_2t = 1.1 ± 0.3, k_2c = 1.8 ± 0.5, k_3t = 1.2 ± 0.4, k_3c = 2.2 ± 0.7.     

Intramolecular carboxylic group‐assisted cleavage of N‐(2‐hydroxyphenyl)phthalamic acid (7) and N‐(2‐methoxyphenyl)phthalamic acid (8): Absence of intramolecular general acid catalysis due to 2‐OH in 7

The values of pseudo first‐order rate constants (k_obs) for the cleavage of N‐(2‐hydroxyphenyl)phthalamic acid ( 7 ), obtained at 4.9 × 10^?2 M HCl, 35°C, and within CH₃CN content range 2–80% (v/v) in mixed aqueous solvent are smaller than k_obs for the cleavage of N‐(2‐methoxyphenyl)phthalamic acid ( 8 ), obtained under almost similar experimental conditions, by nearly 1.5‐ to 2‐fold. These observations show the absence of expected intramolecular general acid catalysis due to 2‐OH group in 7 . The values of k_obs for the cleavage of 7 and 8 decrease by more than 20‐fold with the increase in the content of CH₃CN from 2 to 80–82% (v/v) in mixed aqueous solvent. The kinetic data reveal that in acidic aqueous cleavage of 7 , N‐cyclization (leading to the formation of imide) and O‐cyclization (leading to the formation of phthalic anhydride) vary from ～10 to 15% and ～90 to 85%, respectively, with the increase in CH₃CN content from 2 to 80% (v/v). Similar increase in CH₃CN content causes increase in N‐cyclization from ～0 to 5% and decrease in O‐cyclization from ～100 to 95% in the acidic aqueous cleavage of 8 . Some speculative, yet conceivable, reasons for nearly 10 and 0% N‐cyclization in the cleavage of respective 7 and 8 at low content of CH₃CN have been described. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 746–758, 2006     

Influence of nitroxide structure on the 2,5‐ and 2,6‐spirodicyclohexyl substituted cyclic nitroxide‐mediated free‐radical polymerization of styrene

The 2,6‐spirodicyclohexyl substituted nitroxide, cyclohexane‐1‐spiro‐2′‐(3′,5′‐dioxo‐4′‐benzylpiperazine‐1′‐oxyl)‐6′‐spiro‐1″‐cyclohexane (BODAZ), was investigated as a mediator for controlled/living free‐radical polymerization of styrene. The values of the number‐average molecular weight increased linearly with conversion, but the polydispersities were higher than for the corresponding 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (TEMPO) and 2,5‐bis(spirocyclohexyl)‐3‐benzylimidazolidin‐4‐one‐1‐oxyl (NO88Bn) mediated systems at approximately 2.2 and 1.6 at 100 and 120 °C, respectively. These results were reflected in the rate coefficients obtained by electron spin resonance spectroscopy; at 120 °C, the values of the rate coefficients for polystyrene‐BODAZ alkoxyamine dissociation (k_d), combination of BODAZ and propagating radicals (k_c), and the equilibrium constant (K) were 1.60 × 10^?5 s^?1, 5.19 × 10⁶ M^?1 s^?1, and 3.08 × 10^?12 M, respectively. The value of k_d was approximately one and two orders of magnitude lower, and that of K was approximately 20 and 7 times lower than for the NO88Bn and TEMPO adducts. These results are explained in terms of X‐ray crystal structures of BODAZ and NO88Bn; the six‐membered ring of BODAZ deviates significantly from planarity as compared to the planar five‐membered ring of NO88Bn and possesses a benzyl substituent oriented away from the nitroxyl group leading to a seemingly more exposed oxyl group, which resulted in a higher k_c and a lower k_d than NO88Bn. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3892–3900, 2003     

Free‐Radical Termination Kinetics Studied Using a Novel SP‐PLP‐ESR Technique

Summary: A novel method for measuring termination rate coefficients, k_t, in free‐radical polymerization is presented. A single laser pulse is used to instantaneously produce photoinitiator‐derived radicals. During subsequent polymerization, radical concentration is monitored by time‐resolved electron spin resonance (ESR) spectroscopy. The size of the free radicals, which exhibits a narrow distribution increases linearly with time t, which allows the chain‐length dependence of k_t to be deduced. The method will be illustrated using dodecyl methacrylate polymerization as an example.

Two straight lines provide a very satisfactory representation of the chain‐length dependence of k_t over the entire chain‐length region (c_R = radical concentration).     

Palladium‐Catalyzed Asymmetric Amination of Allenyl Phosphates: Enantioselective Synthesis of Allenes with an Additional Unsaturated Unit

A highly enantioselective Pd‐catalyzed amination of allenyl phosphates generating 2,3‐allenyl amines with central chirality has been developed. Under the optimized conditions, chiral 2,3‐allenyl amines with or without (an) additional C? C double or triple bond(s) have been prepared at 0 °C with up to 90 % yield and 94 % ee by identifying (R)‐3,4,5‐(MeO)₃‐MeOBIPHEP as the ligand.     

Kinetics and mechanism of hydrolysis of N‐(2′‐hydroxyphenyl)phthalamic acid (1) and N‐(2′‐methoxyphenyl)phthalamic Acid (2) in a highly alkaline medium

A kinetic study on hydrolysis of N‐(2′‐hydroxyphenyl)phthalamic acid ( 1 ), N‐(2′‐methoxyphenyl)phthalamic acid ( 2 ), and N‐(2′‐methoxyphenyl)benzamide ( 3 ) under a highly alkaline medium gives second‐order rate constants, k_OH, for the reactions of HO^? with 1, 2 , and 3 as (4.73 ± 0.36) × 10^?8 at 35°C, (2.42 ± 0.28) × 10^?6 and (5.94 ± 0.23) × 10^?5 M^?1 s^?1 at 65°C, respectively. Similar values of k_OH for 3 , N‐methylbenzanilide, N‐methylbenzamide, and N,N‐dimethylbenzamide despite the difference between pK_a values of aniline and ammonia of ～10 pK units are qualitatively explained. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 1–11, 2009     

DFT Rationalization of the Diverse Outcomes of the Iodine(III)‐Mediated Oxidative Amination of Alkenes

A computational study of the mechanism for the iodine(III)‐mediated oxidative amination of alkenes explains the experimentally observed substrate dependence on product distribution. Calculations with the M06 functional have been carried out on the reaction between PhI(N(SO₂Me)₂)₂ and three different representative substrates: styrene, α‐methylstyrene, and (E)‐methylstilbene. All reactions start with electrophilic attack by a cationic PhI(N(SO₂Me)₂)⁺ unit on the double bond, and formation of an intermediate with a single C?I bond and a planar sp² carbocationic center. The major path, leading to 1,2‐diamination, proceeds through a mechanism in which the bissulfonimide initially adds to the alkene through an oxygen atom of one sulfonyl group. This behavior is now corroborated by experimental evidence. An alternative path, leading to an allylic amination product, takes place through deprotonation at an allylic C?H position in the common intermediate. The regioselectivity of this amination depends on the availability of the resonant structures of an alternate carbocationic intermediate. Only in cases where a high electronic delocalization is possible, as in (E)‐methylstilbene, does the allylic amination occur without migration of the double bond.     

Platinum‐Catalyzed Friedel–Crafts‐Type C−H Coupling–Allylic Amination Cascade to Synthesize 3,4‐Fused Tricyclic Indoles

A novel platinum‐catalyzed cascade cyclization reaction was developed by intramolecular Friedel–Crafts‐type C?H coupling of aniline derivatives with a propargyl carbonate unit‐allylic amination sequence. Treatment of various propargyl carbonates tethered to meta‐aniline derivatives with a Pt(dba)₃/DPEphos catalyst system afforded the corresponding 3,4‐fused tricyclic 3‐alkylidene indolines in 42–99 % yield, which were transformed into 3,4‐fused indole derivatives by reaction with trifluoroacetic acid. The reaction products exhibited antiproliferative activities against cancer cells, but not normal cells, revealing the potential usefulness of this reaction for medicinal chemistry.