Iron(MCP) Complexes Catalyze Aziridination with ... - ACS Publications

Apr 12, 2018 - reactions, many of the most synthetically versatile and site- selective iron catalysts are based on MCP-4 (1a−1i) and PDP- type5 liga...
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Cite This: J. Org. Chem. 2018, 83, 5072−5081

Iron(MCP) Complexes Catalyze Aziridination with Olefins As Limiting Reagents Mina F. Shehata,† Suraj K. Ayer,† and Jennifer L. Roizen* Duke University, Department of Chemistry, Box 90346, Durham, North Carolina 27708−0354, United States S Supporting Information *

ABSTRACT: Herein described are the first efficient nitrogenatom transfer reactions mediated by iron N,N′-dimethyl-N,N′bis(2-pyridinylmethyl)cyclohexane-1,2-diamine- (MCP-) and 2({1-[(pyridin-2-ylmethyl)pyrrolidin-2-yl]pyrrolidin-1-yl}methyl)pyridine-type (PDP-type) complexes. These catalysts affect styrene aziridination under mild conditions based on a limiting quantity of olefin substrate.

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INTRODUCTION Molecular nonheme iron complexes catalyze remarkable processes, transforming aliphatic hydrocarbons through hydroxylation1 or dehydrogenation2 and olefins through dihydroxylation or epoxidation (Scheme 1).3 For these oxygen-transfer

relationship between reaction efficiency and MCP- and PDPtype catalyst architecture.

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RESULTS AND DISCUSSION Anticipating that the efficiency of nitrogen-atom transfer process would rely on catalyst architecture, we chose to focus on 2-pyridinylmethyl substitution of the ligand and ligand variations designed to sterically shield the iron center. To investigate the effect of 2-pyridinylmethyl substitution on this nitrogen-transfer process, novel Fe(MCP) complexes 1a−1f have been prepared (Table 1). Throughout this manuscript, the molecular formulas of new metal complexes have been confirmed by elemental analysis. Absent data to confirm connectivity, these complexes are depicted in their acetonitrile solvated forms. MCP-type complexes 1a−1f could adopt cis-α or cis-β topology.10 Closely related Mn4b,11a−c and Fe4c,11d complexes are C2-symmetric with ligands that adopt a cis-α topology. These MCP-type complexes affect nitrogen-transfer to convert olefin 2a to nosyl12 aziridine13,14 3a using [N-(4nitrobenzenesulfonyl)imino]phenyliodane (PhINNs, 4a)15 as a nitrogen source (Table 1). Other aryl sulfonamides16 can serve as nitrogen-transfer precursors to generate aziridine 3b and 3c, albeit in slightly diminished yields. In these aziridination processes, the counterion in the precatalyst impacts reactivity with the most effective complexes incorporating weakly coordinating triflate or perchlorate ions or noncoordinating hexafluoroantimonate ions, rather than strongly coordinating chloride ions. Despite the beneficial effect of 2-pyridinylmethyl-substituted ligands on some oxygen-transfer reactions,11 in this nitrogentransfer process, differential 2-pyridinylmethyl substitution has an insignificant effect on reaction efficiency and enantioinduction. Critically, MCP-ligation of iron improves reaction

Scheme 1. Nonheme Iron Complexes Mediate Alkene Oxidation

reactions, many of the most synthetically versatile and siteselective iron catalysts are based on MCP-4 (1a−1i) and PDPtype5 ligands (1j−1m, Tables 1 and 2). By comparison, fewer nonheme iron complexes are known to advance nitrogentransfer reactions.6−8 Indeed, to our knowledge, neither MCPnor PDP-type complexes have been developed in nitrogentransfer processes. We hypothesized that MCP- and PDP-type iron complexes would affect efficient nitrogen-transfer and that the qualitative reactivity trends for known oxygen-transfer processes would have a predictive value for the developed nitrogen-transfer process. To evaluate these hypotheses, MCPand PDP-type iron complexes have been employed to affect aziridination. While aziridination reactions benefit from the use of a substrate with polarizable and electronically accessible πorbitals to trap the nitrogen-centered oxidant, even the most synthetically promising nonheme iron catalysts with two available coordination sites require an excess of alkene to produce racemic aziridines.9 Herein described is a mild aziridination reaction that employs a limiting quantity of olefin substrate. This system is used to establish a qualitative © 2018 American Chemical Society

Received: February 10, 2018 Published: April 12, 2018 5072

DOI: 10.1021/acs.joc.8b00402 J. Org. Chem. 2018, 83, 5072−5081

Article

The Journal of Organic Chemistry Table 1. Counteranion Influences Aziridination Efficiency; Ligand 2-Pyridinylmethyl Substitution Has Limited Impact

Table 2. Effect of 5-Pyridyl-Substituted MCP-Type and PDP-Type Ligands on Aziridination Reactions

a General reaction conditions: 1.0 equiv of alkene 2a, 1.5 equiv of PhINR (4), 5 mol % [Fe] complex 1, 0.167 M CH3CN, 21 °C. b Isolated yield. cAll complexes provide aziridine 3a as a 1:1 ratio of enantiomers as determined by chiral HPLC. dMetal complexes have been prepared using enantiomerically enriched ligands (see the Supporting Information). eComplex prepared by General Procedure A. f Complex prepared by General Procedure B.

efficiency,17 as Fe(OTf)2 and Fe(ClO4)2·6H2O furnish aziridine 3a in reduced yields (see the Supporting Information). We chose to employ perchlorate complexes in subsequent investigations, noting the higher background conversion with Fe(OTf)2 relative to Fe(ClO4)2·6H2O. In reactions mediated by complex 1a, alkene 2a is not fully consumed, presumably due to catalyst arrest. One catalyst arrest pathway involves oxidative N-dealkylation of the ligand in complex 1a to give ketone 5a (Scheme 2). A similar process is known under oxygen-transfer conditions.17 To further investigate the role of catalyst architecture in nitrogen-transfer processes, iron complexes have been prepared with sterically varied L-type donors (Table 2). Based on similarity to known metal complexes,18−21 these ligands are expected to generate C1- or C2-symmetric metal complexes 1g−1m. In the aziridination of alkene 2a, 5-pyridyl-substituted Fe(MCP) perchlorate 1g and triflate 1h outperform unsubstituted Fe(MCP) complex 1f and Fe(PDP)-type complexes 1j−1m as catalysts (Table 2). Under optimal conditions, olefin 2a reacts with PhINNs (4a) to furnish aziridine 3a in 71% yield at room temperature with 1g as a catalyst (Table 2). Under the same conditions, triflate 1h displays similar catalytic efficacy.

a

General reaction conditions: 1.0 equiv alkene 2a, 1.5 equiv PhINR (4), 5 mol % [Fe] complex 1, 0.167 M CH3CN, 3 h, 21 °C. bIsolated yield. cComplex prepared by General Procedure A. 1.5 h run time. d Complex prepared by General Procedure B. 1.5 h run time.

In practical terms, aziridination methods22 are synthetically important: aziridines are potent pharmacophores,23 ligands for catalysis,24 and versatile precursors to bioactive fine chemicals and materials.25 Nosyl aziridines offer more limited utility as activated electrophiles13 and are readily accessible using the developed method. Under the optimized conditions,26 limiting quantities of electronically varied styrenes react with moderate efficiency to generate racemic aziridines (Table 3, entries 1−9, 14, and 15). The reaction tolerates a pendant acetate, bromine 5073

DOI: 10.1021/acs.joc.8b00402 J. Org. Chem. 2018, 83, 5072−5081

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The Journal of Organic Chemistry Scheme 2. Oxidative N-Dealkylation of the Ligand Proceeds under Reaction Conditions

2-vinylpyridine (entries 10 and 11). These conditions are less effective with unconjugated 1-octene and convert 1-phenylprop-2-en-1-one in modest yields (entries 12 and 13). Moreover, aziridination of isomerically pure cis-1-phenyl-1propene proceeds with erosion of the original olefin geometry (Table 3, entry 14). Other nonheme iron complexes engage reactive nitrogen species28 to affect addition of a nitrogen-centered radical across an olefin or single-electron transfer (SET) pathways (Scheme 2).7b,e,g,29 To indirectly probe the ability of the active oxidant to affect SET under the reaction conditions, we carried out dimerization experiments. SET has been observed in a related system in which an isolable Fe(IV)-tosylimido acts as a oneelectron oxidant to promote N,N-dimethylaniline dimerization.29 Indeed, under the conditions developed herein, selective dimerization of electron-rich aniline 6 suggests that the active oxidant can induce SET from more electron-rich substrates (Scheme 3). By contrast, the active oxidant does not induce

Table 3. General Protocol to Aziridinate Olefins

Scheme 3. Active Oxidant Affects SET from an Arene

dimerization of less oxidatively labile30 benzonitrile (8), which suggests that SET may not be feasible for less oxidatively labile substrates.

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CONCLUSION In conclusion, we have realized an efficient nitrogen-transfer reaction catalyzed by Fe(MCP)- and Fe(PDP)-type complexes. Reaction efficiency is minimally influenced by 2-pyridinylmethyl substitution of the ligand; however, ligand variations that are designed to sterically shield the iron center increase reaction turnover. This aziridination reaction proceeds under mild conditions and does not require the use of excess olefin. Conceptually, nitrogen-transfer technologies mediated by nonheme iron complexes could provide insight into differential reactivity of oxygen- and nitrogen-transfer intermediates. Consequently, we anticipate that this investigation will enable further research to elucidate reactivity differences between ironmediated oxygen- and nitrogen-atom transfer processes.

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EXPERIMENTAL SECTION

General Information. Moisture-sensitive reactions were performed using flame-dried glassware under an atmosphere of dry nitrogen (N2). Air- and water-sensitive reactions, where noted, were performed in an MBraun MB200 glovebox held under an atmosphere of nitrogen gas (working pressure 2−6 mbar). Flame-dried equipment was stored in a 130 °C oven before use and either allowed to cool in a desiccator cabinet or assembled hot and allowed to cool under an inert atmosphere. Air- and moisture-sensitive liquids and solutions were transferred via plastic or glass syringe. Chromatographic purification of products was accomplished using Teledyne Isco CombiFlashRf system using 12−220 g Redi Sep Rf normal phase silica columns (particle size

a

General reaction conditions: 1.0 equiv of alkene 2, 1.5 equiv of PhINNs (4a), 5 mol % [Fe] complex 1g, 0.167 M CH3CN, 21 °C. b Isolated yield. cIsolated as a 91:9 mixture of syn/anti isomers. Analysis of recovered cis-1-phenylpropene from the reaction revealed partial isomerization in the alkene to give a 78:22 ratio cis/trans-1phenylpropene.

atom, nitrile, MIDA boronate ester, phenolic ether, and ketone (entries 2, 5−10). These conditions enable aziridination of challenging substrates, such as 3-vinylestrone27 and Lewis basic 5074

DOI: 10.1021/acs.joc.8b00402 J. Org. Chem. 2018, 83, 5072−5081

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The Journal of Organic Chemistry 40−63 μm irregular, 230−400 mesh). Thin layer chromatography was performed on EMD Millipore silica gel 60 F254 glass-backed plates (layer thickness 250 μm, particle size 10−12 μm, impregnated with a fluorescent indicator). Visualization of the developed chromatogram was accomplished by fluorescence quenching under shortwave UV light and/or by staining with p-anisaldehyde or KMnO4 stains. NMR spectra were obtained on Varian iNOVA spectrometers operating at 400 or 500 MHz for 1H NMR, 101 or 126 MHz for 13C NMR, and 376 MHz for 19F NMR at 23−25 °C, and are reported as chemical shifts (δ) in parts per million (ppm). Spectra were referenced internally according to residual solvent signals (1H, CDCl3, 7.26 ppm; 13 C, CDCl3, 77.0 ppm; acetone-d6, 29.2). Data for NMR spectra use the following abbreviations to describe multiplicity: s, singlet; br s, broad singlet; d, doublet; t, triplet; q, quartet; dd, doublet of doublet; td, triple of doublet; ddd, doublet of doublet of doublets; ddt, doublet of doublet of triplets; app dd, apparent doublet of doublets; ABq, AB system quartet; m, multiplet. Coupling constant (J) are reported in units of Hertz (Hz). IR spectra were obtained on a Nicolet 6700 FTIR system. Peaks are reported in cm−1 with indicated relative intensities: s (strong, 0−33% T); m (medium, 34−66% T); w (weak, 67−100% T); and br (broad). High-resolution mass spectra (HRMS, m/z) were recorded on an Agilent LCMS-TOF-DART spectrometer using electrospray ionization (ESI, Duke University Department of Chemistry Instrumentation Center). Enantiomeric ratios were determined by HPLC Phenomenex Lux Cellulose I in comparison with authentic racemic materials on a Shimadzu Prominence Modular HPLC. All reagents obtained from commercial suppliers were used a received. Preparation and Characterization of Ligand. The ligand was prepared according to a modified literature procedure.31 5-(3,5-Bis(trifluoromethyl)phenyl)-2-(chloromethyl)pyridine (10a). A flame-dried 50 mL round-bottom flask charged with a stir bar was transferred to a nitrogen-filled glovebox where Pd(OAc)2 (74.8 mg, 0.33 mmol, 3 mol %), SPhos (275.1 mg, 0.67 mmol, 6 mol %), 3,5-bis(trifluoromethyl)bromobenzene (3.25 g, 11.1 mmol, 1.0 equiv), and K3PO4 (4.71 g, 22.2 mmol, 2.0 equiv) were added to the flask. The flask was equipped with a reflux condenser, sealed with a Teflon septum, and removed from the glovebox. Toluene (20 mL) and degassed deionized water (2 mL) were added to the flask via syringe followed by 2-(((tert-butyldimethylsilyl)oxy)methyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxabotolan-2-yl)pyridine (5.82 g, 16.6 mmol, 1.5 equiv). The reaction was heated at 100 °C in an oil bath for 16 h, at which time it was allowed to cool to room temperature for 30 min and quenched with water (10 mL). The layers were separated, and the aqueous layer was extracted with CH2Cl2 (3 × 10 mL). The combined organic layers were dried over Na2SO4, filtered, and concentrated under reduced pressure. The crude solid was dissolved in ethanol (15 mL) and 3 N HCl (12 mL). The reaction was vigorously stirred for 3 h, quenched to neutral pH with saturated NaHCO3, and diluted with CH2Cl2 (30 mL). The layers were separated and the aqueous layer was extracted with CH2Cl2 (3 × 20 mL). The combined organic layers were dried over Na2SO4, filtered, and concentrated under reduced pressure to obtain a crude solid. The solid was dissolved in CH2Cl2 (50 mL) and SOCl2 (8.2 mL, 13.2 g, 111 mmol, 10 equiv) was added dropwise via airtight syringe. The reaction was stirred for 12 h and quenched to neutral pH with saturated NaHCO3. The layers were separated, and the aqueous layer was extracted with CH2Cl2 (3 × 20 mL). The combined organic layers were dried over Na2SO4, filtered, and concentrated under reduced pressure to obtain a yellow solid. The yellow solid was purified via silica gel column chromatography using hexanes/EtOAc (95:5) to obtain the desired product as a white solid (2.18 g, 58% yield). 1H NMR (400 MHz, CDCl3) δ 8.82 (d, J = 2.4 Hz, 1H), 8.00 (br s, 2H), 7.97 (d, J = 2.4 Hz, 1H), 7.94−7.91 (m, 1H), 7.64 (d, J = 8.1 Hz, 1H), 4.75 (s, 2H); 13C NMR (126 MHz, CDCl3) δ 157.2, 147.7, 139.5, 135.7, 133.3, 132.6 (q, J = 33.7 Hz), 127.3, 123.0, 123.2 (q, J = 272.8 Hz), 122.0, 46.2; 19F NMR (376 MHz, CDCl3) δ − 62.98; IR (neat) ν 3099 (w), 3023 (w), 2968 (w), 773 (m), 717 (s) cm−1; TLC Rf = 0.62 (hexanes/EtOAc 7:3); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C14H9ClF6N 340.0322; Found 340.0327.

(2R,2′R)-1,1′-Bis((5-(3,5-bis(trifluoromethyl)phenyl)pyridine-2-yl)methyl)-2,2′-bipyrrolidine (10b). A flame-dried 50 mL round-bottom flask was charged with a stir bar, 5-(3,5-bis(trifluoromethyl)phenyl)-2(chloromethyl)pyridine (10a, 0.94 g, 2.75 mmol, 2.2 equiv), (R,R)2,2′-bispyrrolidine/L-tartaric acid (363 mg, 1.25 mmol, 1.0 equiv), NaOH (320 mg, 8 mmol, 6.4 equiv), and 1:1 CH2Cl2/H2O (10 mL) and the reaction was stirred vigorously at room temperature for 12 h. The reaction was then diluted with 1 M NaOH and CH2Cl2 (10 mL). The layers were separated, and the aqueous layer was extracted with CH2Cl2 (5 × 5 mL). The combined organic layers were dried over Na2SO4, filtered, and concentrated under reduced pressure to an orange-yellow solid. The solid was purified via silica gel column chromatography using hexanes/EtOAc (7:3) to obtain the desired product as a white powder (0.45 g, 53% yield). 1H NMR (400 MHz, CDCl3) δ 8.71 (d, J = 2.5 Hz, 1H), 7.93 (s, 2H), 7.88 (s, 1H), 7.81 (dd, J = 8.1, 2.5 Hz, 1H), 7.56 (d, J = 8.1 Hz, 1H), 3.99 (ABq, J = 15.0 Hz, Δν = 283.4 Hz, 4H), 3.13−3.00 (m, 1H), 2.90−2.87 (m, 2H), 2.29 (q, J = 8.2 Hz, 2H), 1.89 (s, 1H), 1.86−1.70 (m, 9H), 1.61 (s, 3H); 13C NMR (126 MHz, CDCl3) δ 161.4, 147.0, 140.1, 134.9, 132.5 (q, J = 32.6 Hz), 131.8, 127.0, 124.2, 123.2 (q J = 273.2 Hz), 121.5, 66.2, 61.0, 55.4, 26.5, 23.7; 19F NMR (376 MHz, CDCl3) δ − 63.01; IR (neat) ν 2959 (s), 717 (m) cm−1; TLC Rf = 0.25 (hexanes/EtOAc 7:3); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C36H31F12N4 747.2357; Found 747.2350. Preparation and Characterization of Iron Complexes: General Procedure A. A flame-dried 10 mL Chemglass microwave vial, charged with a stir bar and ligand (1 equiv), was transferred to a nitrogen-filled glovebox where the solid mixture was treated with iron salt (1 equiv) and acetonitrile (0.09 M). The red suspension was stirred for 16 h at 21 °C, after which point the red solution was filtered using 0.2 μM PTFE syringe filter and concentrated under reduced pressure to obtain the iron complex. The iron complex was stored in glovebox freezer at −36 °C. General Procedure B. A flame-dried 10 mL Chemglass microwave vial, charged with a stir bar and ligand (1 equiv), was transferred to a nitrogen-filled glovebox where the solid mixture was treated with iron(II) chloride (1 equiv) and acetonitrile (0.09 M). The mixture was stirred for 16 h at 21 °C, after which point the orange solution was concentrated under reduced pressure to obtain the iron complex. Then, iron complex (1 equiv) was treated with silver salt (2 equiv) and acetonitrile (0.09 M). The mixture was stirred for an additional 12 h at 21 °C at which point it was stored in glovebox freezer at −36 °C for 4 h. After 4 h, the solution was filtered using 0.2 μM PTFE syringe filter and concentrated under reduced pressure. The crude was dissolved in acetonitrile (1.5 mL), filtered through a pad of Celite, and then concentrated under reduced pressure. The concentrate was again dissolved in acetonitrile (1.5 mL), filtered through a pad of Celite, and then concentrated under reduced pressure. Complex 1a. Prepared from (1R,2R)-N,N′-dimethyl-N,N′-Bis((R)(3,5-di-tert-butyl-phenyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine (39.1 mg, 49.7 μmol, 1 equiv) and iron(II) perchlorate hexahydrate (18.8 mg, 51.8 μmol, 1 equiv) following general procedure A. The complex was obtained as red solid (51.4 mg, quantative yield). Anal. Calcd for C48H68Cl2FeN4O8·2H2O: C, 58.13; H, 7.32; N, 5.65%. Found: C, 58.38; H, 6.88; N, 5.45%; HRMS (ESI-TOF) m/z: [M − 2H2O − 2ClO4]2+ Calcd for C48H68FeN4 378.2396; Found 378.2389. Complex (1a) was also prepared from complex (1c) (102 mg, 0.12 mmol, 1 equiv) and silver perchlorate (51.1 mg, 0.24 mmol, 2 equiv) following general procedure B. The complex was obtained as a brown solid (115 mg, 98% yield). Complex 1b. Prepared from (1R,2R)-N,N′-dimethyl-N,N′-bis((R)(3,5-di-tert-butyl-phenyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine (0.3 mg, 71.7 μmol, 1 equiv) and iron(II) trifluoromethanesulfonate (25.4 mg, 71.7 μmol, 1 equiv) following general procedure A. The complex was obtained as a yellow solid (72 mg, 95% yield). Anal. Calcd for C50H68F6FeN4O6S2·H2O: C, 55.96; H, 6.58; N, 5.22%. Found: C, 55.69; H, 6.24; N, 5.06%; HRMS (ESI-TOF) m/z: [M − 2H2O − 2OTf]2+ Calcd for C48H68FeN4 378.2396; Found 378.2390. 5075

DOI: 10.1021/acs.joc.8b00402 J. Org. Chem. 2018, 83, 5072−5081

Article

The Journal of Organic Chemistry Complex 1c. Prepared from (1R,2R)-N,N′-dimethyl-N,N′-bis((R)(3,5-ditert-butyl-phenyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine (97.8 mg, 0.139 mmol, 1 equiv) and iron(II) chloride (17.6 mg, 0.139 mmol, 1 equiv) following general procedure A. The complex was obtained as an orange solid (114 mg, quantative yield). Anal. Calcd for C48H68Cl2FeN4·1/2H2O: C, 68.89; H, 8.31; N, 6.70%. Found: C, 68.70; H, 8.19, N, 6.65%; HRMS (ESI-TOF) m/z: [M − Cl]+ Calcd for C48H68ClFeN4 791.4482; Found 791.4478. Complex 1d. Prepared from (1R,2R)-N,N′-dimethyl-N,N′-bis((R)(3,5-di-tert-butyl-phenyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine (97.8 mg, 0.139 mmol, 1 equiv), iron(II) chloride (17.6 mg, 0.139 mmol, 1 equiv), and silver hexafluoroantimonate(V) (93.8 mg, 0.274 mmol, 2 equiv) following general procedure B. The complex was obtained as a red solid (180 mg, quantative yield). Anal. Calcd for C48H68F12FeN4Sb2·3H2O: C, 44.95; H, 5.82; N, 4.37%. Found: C, 44.70; H, 5.41; N, 4.41%; HRMS (ESI-TOF) m/z: [M − 2H2O − 2SbF6]2+ Calcd for C48H68FeN4 378.2396; Found 378.2393. Complex 1e. Prepared from (1R,2R)-N,N′-dimethyl-N,N′-bis[Rphenyl(2-pyridinylmethyl)cyclohexane-1,2-diamine (116 mg, 0.243 mmol, 1 equiv) and iron(II) perchlorate hexahydrate (79.4 mg, 0.243 mmol, 1 equiv) following general procedure A. The complex was obtained as a red solid (145 mg, 82% yield). Anal. Calcd for C32H36Cl2FeN4O8·3H2O: C, 48.93; H, 5.39; N, 7.13%. Found: C, 48.68; H, 4.93; N, 7.18%; HRMS (ESI-TOF) m/z: [M − 2H2O − 2ClO4]2+ Calcd for C32H36FeN4 266.1144; Found 266.1144. Complex 1f. Prepared from (1R,2R)-N,N′-dimethyl-N,N′-bis(2pyridinylmethyl)cyclohexane-1,2-diamine (73.7 mg, 0.227 mmol, 1 equiv) and iron(II) perchlorate hexahydrate (82.6 mg, 0.227 mmol, 1 equiv) following general procedure A. The complex was obtained as a red solid (136.4 mg, 91% yield). Anal. Calcd for C20H32Cl2FeN4O8· 2.35H2O: C, 38.65; H, 5.30; N, 9.01%. Found: C, 38.25; H, 4.89; N, 8.66%. HRMS (ESI-TOF) m/z: [M − 2H2O − 2ClO4]2+ Calcd for C22H32FeN4 190.0832; Found 190.0832. Complex 1g. Prepared from (1R,2R)-N,N′-dimethyl-N,N′-bis(5triisopropylsilyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine (134 mg, 0.211 mmol, 1 equiv) and iron(II) perchlorate hexahydrate (76.9 mg, 0.211 mmol, 1 equiv) following general procedure A. The complex was obtained as a brownish-yellow solid (206 mg, quantative yield). Anal. Calcd for C38H68Cl2FeN4O8Si2·(H2O)(MeCN): C, 50.52; H, 7.74; N, 7.36%. Found: C, 50.69; H, 7.69; N, 7.48%; HRMS (ESI-TOF) m/z: [M − 2H2O − 2ClO4]2+ Calcd for C38H68FeN4Si2 346.2160; Found 346.2159. Complex 1g was also prepared from (1R,2R)-N,N′dimethyl-N,N′-bis(5-triisopropylsilyl)-2-pyridinylmethyl)cyclohexane1,2-diamine (41.7 mg, 0.0655 mmol, 1 equiv), iron(II) chloride (8.30 mg, 0.065 mmol, 1 equiv), and silver perchlorate (27.1 mg, 0.13 mmol, 2 equiv) following general procedure B. The complex was obtained as red solid (58.3 mg, 98% yield). Complex 1h. Prepared from (1R,2R)-N,N′-dimethyl-N,N′-bis(5triisopropylsilyl)-2-pyridinylmethyl)cyclohexane-1,2-diamine (34.2 mg, 53.7 μmol, 1 equiv), iron(II) trifluoromethanesulfonate (19.0 mg, 53.7 μmol, 1 equiv), and acetonitrile (1 mL) following general procedure A. The complex was obtained as a yellow solid (51 mg, 96% yield). Anal. Calcd for C40H68F6FeN4O6S2Si2·H2O: C, 47.61; H, 6.99; N, 5.55%. Found: C, 47.65; H, 6.91; N, 5.60%; HRMS (ESI-TOF) m/ z: [M − 2H2O − 2OTf]2+ Calcd for C38H68FeN4Si2 346.2160; Found 346.2161. Complex 1i. Prepared from (1R,2R)-N,N′-bis((5-(2,6-bis(trifluoromethyl)phenyl)pyridine-2-yl)methyl)dimethyl cyclohexane1,2-diamine (89.0 mg, 0.119 mmol, 1 equiv), iron(II) perchlorate hexahydrate (43.2 mg, 0.119 mmol, 1 equiv) following general procedure A. The complex was obtained as a red solid (113 mg, 88% yield). Anal. Calcd for C36H32Cl2F12FeN4O8·H2O: C, 42.33; H, 3.36; N, 5.47; F, 22.32%. Found: C, 42.66; H, 3.37; N, 5.71; F, 22.14%; HRMS (ESI) m/z: [M − H2O − 2ClO4]2+ Calcd for C36H32F12FeN4 402.0892; Found 402.0888. Complex 1j. Prepared from (2R,2R)-1,1′-bis(pyridin-2-ylmethyl)2,2′-bipyrrolidine (50.5 mg, 0.157 mmol, 1 equiv) and iron(II) perchlorate hexahydrate (56.4 mg, 0.157 mmol, 1 equiv) following general procedure A. The complex was obtained as a red solid (89.7 mg, quantative yield). Anal. Calcd for C20H26Cl2FeN4O8·2H2O: C,

39.17; H, 4.93; N, 9.14%. Found: C, 39.42; H, 4.70; N, 9.05%; HRMS (ESI-TOF) m/z: [M − 2ClO4]2+ Calcd for C20H26FeN4 189.0754; Found 189.0748. Complex 1k. Prepared from (2R,2R)-1,1′-bis(5-triisopropylsilyl)pyridin-2-yl)methyl))-2,2′-bipyrrolidine (100 mg, 0.157 mmol, 1 equiv) and iron(II) perchlorate hexahydrate (57.1 mg, 0.157 mmol, 1 equiv) following general procedure A. The complex was obtained as a red solid (137 mg, quantative yield). Anal. Calcd for C38H66Cl2FeN4O8Si2·H2O: C, 50.27; H, 7.55; N, 6.17%. Found: C, 49.99; H, 7.24; N, 6.25%; HRMS (ESI-TOF) m/z: [M − 2ClO4]2+ Calcd for C38H66FeN4Si2 345.2088; Found 345.2087. Complex 1l. Prepared from (2R, 2′R)-1,1′-bis((5-(3,5-bis(trifluoromethyl)phenyl)pyridine-2-yl)methyl)-2,2′-bipyrrolidine (50.0 mg, 0.067 mmol, 1 equiv) and iron(II) perchlorate hexahydrate (24.3 mg, 0.067 mmol, 1 equiv) following general procedure A. The complex was obtained as a red solid (62 mg, 92% yield). Anal. Calcd for C36H30Cl2FeF12N4O8·3H2O: C, 40.97; H, 3.44; N, 5.31; F, 21.60%. Found: C, 41.23; H, 3.32; N, 5.35; F, 21.24%; HRMS (ESI-TOF) m/ z: [M − 2MeCN − 2ClO4]2+ Calcd for C36H30F12FeN4 401.0809; Found 401.0808. Complex 1m. Prepared from 1-methyl-2-((2R,2′R)-1′-(5triisopropylsilyl)pyridine-2-yl)methyl)-2,2′-bipyrrolidin-1-yl)methyl)1H-benzo[d]imidazole (100 mg, 0.188 mmol, 1 equiv) and iron(II) perchlorate hexahydrate (68.2 mg, 0.188 mmol, 1 equiv) following general procedure A. The complex was obtained as a red solid (149 mg, quantative yield). Anal. Calcd for C32H49Cl2FeN5O8Si·H2O: C, 48.86; H, 6.28; N, 8.90%. Found: C, 48.89; H, 6.49; N, 8.77%. HRMS (ESI) m/z: [M − H2O − 2ClO4−]2+ Calcd for C32H49FeN5Si 293.6553; Found 293.6549. Complex 1n. Prepared from (S)-1-(1-ethyl-1H-benzo[d]imidazol2-yl)-N-((1-((1-ethyl-1H-benzo[d]imidazol-2-yl)methyl)pyrrolidin-2yl)methyl)-N-methylmethanamine (100 mg, 0.250 mmol, 1 equiv) and iron(II) perchlorate hexahydrate (92.6 mg, 0.255 mmol, 1 equiv) following general procedure A. The complex was obtained as a red solid (164 mg, quantitative yield). Anal. Calcd for C24H30Cl2FeN6O8· 1/2H2O: C, 43.26; H, 4.69; N, 12.61%. Found: C, 43.08; H, 4.64; N, 12.94%; HRMS (ESI-TOF) m/z: [M − 2MeCN − 2ClO4]2+ Calcd for C24H30FeN6 229.0940; Found 229.0935. Preparation and Characterization of Iminoiodinanes. [N-(4Nitrobenzenesulfonyl)imino]phenyliodinane (4a). The compound was prepared according to a modified literature procedure.32 A flamedried 250 mL round-bottom flask was charged with a stir bar, 4nitrobenzenesulfonamide (1.25 g, 6.18 mmol, 1 equiv), potassium hydroxide (0.706 g, 12.58 mmol, 2 equiv), and methanol (150 mL). The yellow suspension was stirred at 21 °C until all of the solid was dissolved. Then, diacetoxyiodobenzene (2.5 g, 7.78 mmol, 1.25 equiv) was added to the clear yellow solution and the mixture was stirred at 21 °C for 4 h. The resulting yellow precipitate was filtered, washed with water (3 × 100 mL) and methanol (3 × 100 mL), and dried under reduced pressure over P2O5 overnight to obtain product as pale yellow solid (1.55 g, 62% yield). The compound could be stored at 2− 8 °C up to 3−5 weeks. 1H NMR (400 MHz, d6-DMSO) δ 8.03 (d, J = 7.7, 1H), 7.71 (t, J = 7.7 Hz, 4H), 7.40 (t, J = 7.4 Hz, 1H), 7.25 (t, J = 7.8 Hz, 2H). [N-(4-tert-butylbenzenesulfonyl)imino]phenyliodinane (4c). The compound was prepared according to a modified literature procedure.33 A flame-dried 250 mL round-bottom flask was charged with a stir bar, 4-tert-butyl benzenesulfonamide (166 mg, 0.78 mmol, 1 equiv), potassium hydroxide (87.5 mg, 1.56 mmol, 2 equiv), and methanol (20 mL). The solution was cooled to 0 °C (ice/water bath), and diacetoxyiodobenzene (250 mg, 0.78 mmol, 1 equiv) was added to the clear yellow solution and the mixture was stirred at 0 °C for 3 h. The resulting yellow solution was poured into chilled 30 mL of deionized water causing precipitate to form. The suspension was left to settle for an hour in the freezer (2−8 °C). The resulting yellow precipitate was then filtered, washed with hexanes (30 mL), and dried under reduced pressure over P2O5 overnight to obtain product as yellow solid (192 mg, 59% yield). The compound could be stored stored at 2−8 °C up to 3−5 weeks. 1H NMR (500 MHz, d6-DMSO) δ 7.64 (d, J = 7.4 Hz, 2H), 7.46 (d, J = 7.8 Hz, 2H), 7.41 (t, J = 7.4 Hz, 5076

DOI: 10.1021/acs.joc.8b00402 J. Org. Chem. 2018, 83, 5072−5081

Article

The Journal of Organic Chemistry

with diethyl ether (3 × 15 mL). The combined organic layers were washed with deionized water (3 × 15 mL), dried over Na2SO4, filtered, and concentrated under reduced pressure to obtain an orange solid. The crude orange solid was purified by silica gel column chromatography using hexanes/EtOAc (9:1) to obtain the desired product as a white solid (0.367 g, 33% yield). 1H NMR (400 MHz, CDCl3) δ 7.52 (s, 1H), 7.43−7.38 (m, 4H), 7.34−7.33 (m, 1H), 6.77 (dd, J = 18.1, 11.1 Hz, 1H), 5.81 (d, J = 17.9 Hz, 1H), 5.30 (d, J = 11.1 Hz, 1H), 4.90 (s, 2H), 3.73 (s, 2H), 1.44 (s, 9H), 1.34 (s, 9H); 13C NMR (126 MHz, CDCl3) δ 153.7, 147.3, 143.0, 138.2, 137.5, 136.8, 129.1, 126.1, 125.9, 125.3, 125.1, 124.5, 123.9, 114.4, 75.5, 35.8, 34.9, 31.6, 31.5, 19.4; IR (neat) ν 3001 (w), 2958 (m), 2901 (w), 2866 (w), 2251 (w), 1602 (w) cm−1; TLC Rf = 0.2 (hexanes/EtOAc, 9:1); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C25H31NO 361.2406; Found 361.2408. Preparation and Characterization of Aziridines. General Procedure for Aziridination. Reactions were performed on 0.25 mmol scale, unless otherwise specified. A flame-dried 10 mL Chemglass microwave vial was charged with a stir bar, 4-vinylbiphenyl (45.1 mg, 0.25 mmol, 1 equiv), and [N-(4-nitrobenzenesulfonyl)imino] phenyliodinane (151 mg, 0.375 mmol, 1.5 equiv). The vial was transferred to a nitrogen-filled glovebox where iron complex (12.13 mg, 0.0125 mmol, 5 mol %) and acetonitrile (1.5 mL) were added to the vial. The resulting orange suspension was stirred at 21 °C for 1.5 h, after which point the reaction was concentrated under reduced pressure. The desired product was isolated by silica gel column chromatography (conditions given below). Deviations from this procedure are specified below. 2-([1,1′-Biphenyl]-4-yl)-1-((4-nitrophenyl)sulfonyl)aziridine (3a). Prepared from 4-vinylbiphenyl and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane following the general procedure for aziridination. The product was obtained as a white solid (68.2 mg, 71% yield) after silica gel column chromatography using hexanes/EtOAc (9:1). 1 H NMR (400 MHz, CDCl3) δ 8.4 (d, J = 8.5 Hz, 2H), 8.21 (d, J = 8.5 Hz, 2H), 7.54 (d, J = 8.4 Hz, 4H), 7.43 (t, J = 7.6 Hz, 2H), 7.37−7.34 (m, 1H), 7.29 (d, J = 7.9 Hz, 2H), 3.95 (dd, J = 4.7, 7.2 Hz, 1H), 3.15 (d, J = 7.2 Hz, 1H), 2.55 (d, J = 4.6 Hz, 1H); 13C NMR (126 MHz, CDCl3) δ 150.9, 144.1, 142.0, 140.4, 133.3, 129.4, 129.1, 127.8, 127.7, 127.2, 127.1, 125.6, 41.9, 36.8 ; IR (neat) ν 3103 (w), 3032 (w), 2869 (w), 1527 (s), 1347 (m), 1333 (m), 1161 (s) cm−1; TLC Rf = 0.17 (hexanes/EtOAc, 9:1); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C20H16N2O4S 380.0831; Found 380.0830. 2-([1,1′-Biphenyl]-4-yl)-1-tosylaziridine (3b). Prepared from 4vinylbiphenyl and 4-methyl-N-(phenyl-λ3-iodaneylidene)pyridine-2sulfonamide following the general procedure for aziridination. The product was obtained as a white solid (56.1 mg, 64% yield) after silica gel column chromatography using hexanes/EtOAc (9:1). The characterization data for the compound were in agreement with previously published information.38 1H NMR (500 MHz, CDCl3) δ 7.89 (d, J = 8.3 Hz, 2H), 7.57−7.49 (m, 4H), 7.43 (t, J = 7.6 Hz, 2H), 7.35 (dd, J = 7.8, 2.6 Hz, 3H), 7.29 (d, J = 8.2 Hz, 2H), 3.82 (dd, J = 7.2, 4.5 Hz, 1H), 3.02 (d, J = 7.2 Hz, 1H), 2.44−2.43 (m, 4H). 2-([1,1′-Biphenyl]-4-yl)-1-((4-(tert-butyl)phenyl)sulfonyl)aziridine (3c). Prepared from 4-vinylbiphenyl and 4-(tert-butyl)-N-(phenyl-λ3iodaneylidene)pyridine-2-sulfonamide following the general procedure for aziridination. The product was obtained as a white solid (51 mg, 52% yield) after silica gel column chromatography using hexanes/ EtOAc (9:1). 1H NMR (500 MHz, CDCl3) δ 7.92 (d, J = 8.2 Hz, 2H), 7.57−7.52 (m, 6H), 7.43 (t, J = 7.6 Hz, 2H), 7.36−7.31 (m, 1H), 7.31 (d, J = 7.9 Hz, 2H), 3.85 (dd, J = 4.5, 7.2 Hz, 1H), 3.02 (d, J = 7.2 Hz, 1H), 2.44 (d, J = 4.5 Hz, 1H), 1.35 (s, 9H); 13C NMR (126 MHz, CDCl3) δ 157.8, 141.5, 140.7, 135.1, 134.3, 129.0, 128.0, 127.7, 127.5, 127.3, 126.4, 41.0, 36.3, 35.5, 31.3 ; IR (neat) ν 2962 (s), 2868 (w), 1359 (s), 1158 (m) cm−1; TLC Rf = 0.14 (hexanes/EtOAc, 9:1); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C24H25NO2S 391.1606; Found 391.1605. 1-((4-Nitrophenyl)sulfonyl)-2-phenylaziridine (3d). Prepared from styrene and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane after 3 h following the general procedure for aziridination. The product was obtained as a white solid (56 mg, 73% yield) after silica gel column

1H), 7.27−7.23 (m, 4H), 1.24 (s, 9H); 13C NMR (126 MHz, CDCl3) δ 152.9, 142.1, 133.1, 130.5, 130.1, 125.9, 124.9, 116.7, 34.4, 30.9; IR (neat) 2964 (w), 2867 (w), 1364 (w) cm−1; HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C16H18INO2S 415.0103; Found 415.0103. Preparation and Characterization of Olefins. 4-Vinyl-1,1′biphenyl (2a). The compound was prepared according to a modified literature procedure.34 A flame-dried 250 mL round-bottom flask was charged with a stir bar, phenyl boronic acid (2.45 g, 20.1 mmol, 1.2 equiv), tri(o-tolyl)phosphine (0.51 g, 1.69 mmol, 0.1 equiv), and barium hydroxide octahydrate (6.34 g, 20.1 mmol, 1.2 mmol). The flask was equipped with a reflux condenser, sealed with a rubber septum, and transferred to glovebox where palladium acetate (0.92 g, 4.1 mmol, 0.05 equiv) was added to the flask. The sealed flask was then removed from the glovebox. 4-Vinylbromobenzene (2.20 mL, 16.83 mmol, 1 equiv), dimethoxyethane (80 mL), and degassed DI water (30 mL) were added sequentially to the reaction via syringe. The suspension was then stirred at 80 °C for 4 h under nitrogen atmosphere. The black suspension was vacuum filtered and the filtrate was concentrated under reduced pressure to remove dimethoxymethane. The aqueous suspension was transferred to a separatory funnel and extracted with dichloromethane (3 × 50 mL). The combined organic layers were dried over Na2SO4, filtered, and concentrated under reduced pressure to obtain a pale white solid. The pale white solid was purified by silica gel column chromatography using hexanes to obtain the desired product as a white solid (2.65 g, 88% yield). The compound was stored at 2−8 °C. The characterization data for the compound were in agreement with previously published information.35 1H NMR (400 MHz, CDCl3) δ 7.60 (d, J = 6.9, 2H), 7.57 (d, J = 8.3 Hz, 2H); 7.49 (d, J = 8.3 Hz, 2H), 7.44 (t, J = 7.7 Hz, 2H), 7.35 (t, J = 7.4 Hz, 1H), 6.76 (dd, J = 17.6, 10.9 Hz, 1H), 5.80 (d, J = 17.6 Hz, 1H), 5.28 (d, J = 10.9 Hz, 1H). 6-Methyl-2-(4-vinylphenyl)-1,3,6,2-dioxazaborocane-4,8-dione (2j). The compound was prepared according to the modified literature procedure.36 A 500 mL round-bottom flask was charged with a stir bar, flame-dried under vacuum, and allowed to cool to 21 °C under nitrogen atmosphere. 4-Vinylphenylboronic acid (0.500 g, 3.39 mmol, 1.0 equiv) and N-methyliminodiacetic acid (0.497 g, 3.39 mmol, 1.0 equiv) were added to the flask and the flask was equipped with a reflux condenser and sealed with a rubber septum. It was thrice evacuated under vacuum and backfilled with nitrogen. The mixture of solids was treated with benzene (55 mL) and DMSO (6 mL) via syringe, and the resulting mixture was refluxed 80 °C under nitrogen atmosphere for 16 h. The yellow solution was concentrated under reduced pressure to remove benzene and the remaining solution was diluted with deionized water (50 mL). A precipitate formed immediately. The aqueous suspension was transferred to a separatory funnel and extracted with ethyl acetate (3 × 50 mL). The combined organic layers were dried over Na2SO4, filtered, and concentrated under reduced pressure to obtain a crude liquid which was purified by silica gel column chromatography using hexanes/EtOAc (2:8) to obtain the desired product as a white solid (0.64 g, 74% yield). 1H NMR (500 MHz, CDCl3) δ 7.50−7.21 (m, 4H), 6.75 (dd, J = 17.7, 10.9 Hz, 1H), 5.82 (d, J = 17.6 Hz, 1H), 5.24 (d, J = 10.9 Hz, 1H), 4.25 (d, J = 16.9 Hz, 2H), 4.06 (d, J = 16.8 Hz, 2H), 2.56 (s, 3H) ; 13C NMR (126 MHz, CDCl3) δ 169.2, 139.0, 137.4, 133.5, 126.3, 114.6, 62.5, 48.1 ; IR (neat) ν 3106 (w), 2926 (w), 2858 (w), 1742 (s), 1608 (w) cm−1; TLC Rf = 0.5 (EtOAc); HRMS (ESI−TOF) m/z: [M + H]+ Calcd for C13H14BNO4 260.1089; Found 260.1090. 2-(3,5-Ditert-butyl-2-((3-vinylbenzyl)oxy)phenyl)acetonitrile (2k). The compound was prepared according to the modified literature procedure.37 A flame-dried 50 mL round-bottom flask was charged with 2-(3,5-di-tert-butyl-2-hydroxyphenyl)acetonitrile (764 mg, 3.12 mmol, 1.0 equiv), dry DMF (11 mL), and the solution was chilled in an ice/water bath at 0 °C. Sodium hydride (60% w/w, 140 mg, 3.5 mmol, 1.1 equiv) was added to the solution at 0 °C. Once effervescence stopped, 1-(bromomethyl)-3-vinylbenzene (612 mg, 3.12 mmol, 1 equiv) was added dropwise via a syringe at 0 °C under nitrogen atmosphere, and the reaction was stirred for 5 h. The reaction was quenched by the addition of deionized water (10 mL) and the layers were separated. The aqueous layer was then extracted 5077

DOI: 10.1021/acs.joc.8b00402 J. Org. Chem. 2018, 83, 5072−5081

Article

The Journal of Organic Chemistry

62.5, 48.2, 41.9, 37.0; IR (neat) ν 2957 (w), 2925 (w), 2856 (w), 1731 (m), 1529 (m), 1334 (m), 1161 (s) cm−1; TLC Rf = 0.24 (hexanes/ EtOAc, 2:8); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C19H18BN3O8S 460.0980; Found 460.0977. 2-(3,5-Ditert-butyl-2-((3-(1-((4-nitrophenyl)sulfonyl)aziridin-2-yl)benzyl)oxy)phenyl) Acetonitrile (3k). Prepared from 2-(3,5-ditertbutyl-2-((3-vinylbenzyl)oxy)phenyl)acetonitrile (2k) and [N-(4nitrobenzenesulfonyl)imino]phenyliodinane after 3 h following the general procedure for aziridination. The product was obtained as a white solid (80.2 mg, 58% yield) after silica gel column chromatography using hexane/EtOAc (9:1). 1H NMR (500 MHz, CDCl3) δ 8.39 (d, J = 8.9 Hz, 2H), 8.21 (d, J = 8.4 Hz, 2H), 7.48−7.42 (m, 1H), 7.42−7.35 (m, 3H), 7.31 (d, J = 2.4 Hz, 1H), 7.23 (dt, J = 7.4, 1.6 Hz, 1H), 4.88 (s, 2H), 3.97 (dd, J = 7.2, 4.6 Hz, 1H), 3.68 (s, 2H), 3.14 (d, J = 7.2 Hz, 1H), 2.55 (d, J = 4.5 Hz, 1H), 1.41 (s, 9H), 1.33 (s, 9H); 13C NMR (126 MHz, CDCl3) δ 153.5, 150.9, 147.4, 144.0, 142.9, 138.0, 135.0, 129.4, 129.3, 126.9, 126.2, 125.4, 125.2, 124.6, 124.5, 123.7, 118.8, 75.0, 41.8, 37.0, 35.7, 34.8, 31.6, 31.5, 19.3; IR (neat) ν 3104 (w), 3056 (w), 2962 (w), 2869 (w), 1532 (m), 1348 (w), 1337 (w), 1164 (w) cm−1; TLC Rf = 0.12 (hexanes/EtOAc, 7:1); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C31H35N3O5S 561.2297; Found 561.2297. (8R,9S,13S,14S)-13-Methyl-3-(1-((4-nitrophenyl)sulfonyl)aziridin2-yl)-6,7,8,9,11,12,13,14,15,16-decahydro-17H-cyclopenta[a]phenanthren-17-one (3l). Prepared from (8R,9S,13S,14S)-13-methyl3-vinyl-6,7,8,9,11,12,13,14,15,16-decahydro-17H-cyclopenta[a]phenanthren-17-one and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane following the general procedure for aziridination. The product was obtained as an off white solid (53 mg, 44% yield) after silica gel column chromatography using hexane/EtOAc (8:2). 1H NMR (400 MHz, CDCl3) δ 8.38 (d, J = 8.8 Hz, 2H), 8.18 (d, J = 8.8 Hz, 2H), 7.24 (d, J = 8.4 Hz, 1H), 6.99 (dd, J = 8.1, 2.1 Hz, 1H), 6.95 (d, J = 1.9 Hz, 1H), 3.85 (dd, J = 7.2, 4.6 Hz, 1H), 3.08 (d, J = 7.2 Hz, 1H), 2.87 (dd, J = 8.9, 4.3 Hz, 2H), 2.53−2.47 (m, 2H), 2.41−2.22 (m, 3H), 2.19−1.92 (m, 6H), 1.60−1.44 (m, 6H), 0.89 (s, 3H); 13C NMR (126 MHz, CDCl3) δ 220.6, 150.6, 144.0, 140.6, 137.1, 131.5, 129.2, 127.0, 127.0, 125.8, 124.3, 123.8, 123.8, 50.4, 47.8, 44.3, 41.8, 41.7, 38.0, 36.4, 35.8, 31.5, 29.3, 26.3, 25.6, 21.5, 13.8; IR (neat) ν 3106 (w), 2925 (w), 2857 (w), 1741 (m), 1527 (m), 1347 (m), 1325 (m), 1157 (s) cm−1; TLC Rf = 0.32 (hexanes/EtOAc, 8:2); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C26H28N2O5S 481.1792; Found 481.1792. 2-(1-((4-Nitrophenyl)sulfonyl)aziridin-2-yl)pyridine (3m). Prepared from 2-vinylpyridine and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane after 3 h following the general procedure for aziridination. The product was obtained as an orange solid (35 mg, 46% yield) after silica gel column chromatography using hexane/ EtOAc (5:5). 1H NMR (400 MHz, CDCl3) δ 8.59−8.49 (m, 1H), 8.43−8.32 (m, 2H), 8.24−8.16 (m, 2H), 7.67 (td, J = 7.7, 1.8 Hz, 1H), 7.34−7.19 (m, 2H), 4.03 (dd, J = 7.3, 4.5 Hz, 1H), 3.11 (d, J = 7.3 Hz, 1H), 2.83 (d, J = 4.5 Hz, 1H); 13C NMR (126 MHz, CDCl3) δ 153.2, 150.7, 149.9, 143.6, 136.9, 129.4, 124.3, 123.7, 122.0, 42.0, 35.4; IR (neat) ν 3105 (w), 2924 (w), 1530 (m), 1350 (m), 1310 (w), 1166 (s) cm−1; TLC Rf = 0.25 (hexanes/EtOAc, 7:3); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C13H11N3O4S 306.0543; Found 306.0544. 2-Hexyl-1-((4-nitrophenyl)sulfonyl)aziridine (3n). Prepared from 1-octene and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane after 3 h following the general procedure for aziridination. The product was obtained as a white solid (21 mg, 27% yield) after silica gel column chromatography using hexane/EtOAc (9:1). The characterization data for the compound were in agreement with previously published information.40 1H NMR (400 MHz, CDCl3) δ 8.39 (d, J = 8.7 Hz, 2H), 8.16 (d, J = 8.7 Hz, 2H), 2.88 (tt, J = 7.2, 4.9 Hz, 1H), 2.74 (d, J = 7.1 Hz, 1H), 2.16 (d, J = 4.7 Hz, 1H), 1.63−1.52 (m, 2H), 1.45− 1.31 (m, 2H), 1.30−1.16 (m, 8H), 0.85 (t, J = 6.9 Hz, 3H). (1-((4-Nitrophenyl)sulfonyl)aziridin-2-yl)(phenyl)methanone (3o). Prepared from 1-phenylprop-2-en-1-one and [N-(4nitrobenzenesulfonyl)imino]phenyliodinane following the general procedure for aziridination. The product was obtained as a white solid (34 mg, 41% yield) after silica gel column chromatography using

chromatography using hexanes/EtOAc (9:1). The characterization data for the compound were in agreement with previously published information.39 1H NMR (400 MHz, CDCl3) δ 8.37 (d, J = 8.8 Hz, 2H), 8.19 (d, J = 8.8 Hz, 2H), 7.31 (m, 3H), 7.22 (m, 2H), 3.90 (dd, J = 7.2, 4.4 Hz, 1H), 3.11 (d, J = 7.6 Hz, 1H), 2.50 (d, J = 4.4 Hz, 1H). 1-((4-Nitrophenyl)sulfonyl)-2-phenylaziridine (3e). Prepared from 4-acetoxystyrene and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane after 3 h following the general procedure for aziridination. The product was obtained as a white solid (62.5 mg, 69% yield) after silica gel column chromatography using hexanes/ EtOAc (9:1). The characterization data for the compound were in agreement with previously published information.14d 1H NMR (400 MHz, CDCl3) δ 8.39 (d, J = 8.8 Hz, 2H), 8.19 (d, J = 8.8 Hz, 2H), 7.23 (d, J = 8.6 Hz, 2H), 7.04 (d, J = 8.5 Hz, 2H), 3.89 (dd, J = 7.2, 4.5 Hz, 1H), 3.11 (d, J = 7.2 Hz, 1H), 2.29 (s, 2H). 2-(4-tert-Butyl)phenyl)-1-((4-nitrophenyl)sulfonyl)aziridine (3f). Prepared from 4-tertbutylstyrene and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane after 3 h following the general procedure for aziridination. The product was obtained as a white solid (56.1 mg, 62% yield) after silica gel column chromatography using hexanes/EtOAc (9:1). The characterization data for the compound were in agreement with previously published information.39 1H NMR (400 MHz, CDCl3) δ 8.38 (d, J = 8.9 Hz, 2H), 8.19 (d, J = 8.8 Hz, 2H), 7.34 (d, J = 8.4 Hz, 2H), 7.14 (d, J = 8.3 Hz, 2H), 3.89 (dd, J = 7.3, 4.7 Hz, 1H), 3.10 (d, J = 7.2 Hz, 1H), 2.51 (d, J = 4.7 Hz, 1H), 1.29 (s, 1H). 2-(4-Bromophenyl)-1-((4-nitrophenyl)sulfonyl)aziridine (3g). Prepared from 4-bromostyrene and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane following the general procedure for aziridination. The product was obtained as an off-white solid (56.5 mg, 59% yield) after silica gel column chromatography using hexanes/EtOAc (9:1). The characterization data for the compound were in agreement with previously published information.39 1H NMR (400 MHz, CDCl3) δ 8.39 (d, J = 8.8 Hz, 2H), 8.18 (d, J = 8.9 Hz, 2H), 7.45 (d, J = 8.5 Hz, 2H), 7.10 (d, J = 8.4 Hz, 2H), 3.86 (dd, J = 7.1, 4.4 Hz, 1H), 3.11 (d, J = 7.3 Hz, 1H), 2.46 (d, J = 4.6 Hz, 1H). 4-(1-((4-Nitrophenyl)sulfonyl)aziridine-2-yl)benzonitrile (3h). Prepared from 4-cyanostyrene and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane after 3 h following the general procedure for aziridination. The product was obtained as a pale yellow solid (52.4 mg, 61% yield) after silica gel column chromatography using hexanes/ EtOAc (9:1). The characterization data for the compound were in agreement with previously published information.14d 1H NMR (400 MHz, CDCl3) δ 8.41 (d, J = 8.8 Hz, 2H), 8.19 (d, J = 8.8 Hz, 2H), 7.63 (d, J = 8.3 Hz, 2H), 7.36 (d, J = 8.2 Hz, 2H), 3.94 (dd, J = 7.2, 4.4 Hz, 1H), 3.14 (d, J = 7.3 Hz, 1H), 2.46 (d, J = 4.4 Hz, 1H). 2-(1-((4-Nitrophenyl)sulfonyl)aziridine-2-yl)benzonitrile (3i). Prepared from 2-cyanostyrene and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane after 3 h following the general procedure for aziridination. The product was obtained as a pale yellow solid (55.2 mg, 67% yield) after silica gel column chromatography using hexanes/ EtOAc (9:1). 1H NMR (500 MHz, CDCl3) δ 8.43−8.40 (m, 2H), 8.25−8.22 (m, 2H), 7.65 (d, J = 8.0 Hz, 1H), 7.56 (td, J = 7.7, 1.1 Hz, 1H), 7.42 (td, J = 7.7, 1.1 Hz, 1H), 7.29 (d, J = 8.2 Hz, 1H), 4.19 (dd J = 7.0, 4.6 Hz, 1H), 3.22 (d, J = 7.1 Hz, 1H), 2.52 (d, J = 4.6 Hz, 1H); 13 C NMR (126 MHz, CDCl3) δ 151.1, 143.4, 138.1, 133.5, 133,2, 129.7, 129.3, 126.7, 124.7, 116.9, 112.3, 39.5, 36.8 ; IR (neat) ν 3107 (w), 2924 (w), 2227 (w), 1529 (s), 1340 (m), 1310 (m), 1165 (s) cm−1; TLC Rf = 0.14 (hexanes/EtOAc, 8:2); HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C15H11N3O4S 329.0470; Found 329.0470. 6-Methyl-2-(4-(1-((4-nitrophenyl)sulfonyl)aziridin-2-yl)phenyl)1,3,6,2-dioxazaborocane-4,8-dione (3j). Prepared from 6-methyl-2(4-vinylphenyl)-1,3,6,2-dioxazaborocane-4,8-dione (2j) and [N-(4nitrobenzenesulfonyl)imino]phenyliodinane following the general procedure for aziridination. The product was obtained as a white solid (63 mg, 55% yield) after silica gel column chromatography using hexane/EtOAc (3:7). 1H NMR (400 MHz, CD3CN) δ 8.38 (d, J = 8.7 Hz, 1H), 8.18 (d, J = 8.8 Hz, 1H), 7.46 (d, J = 7.7 Hz, 1H), 7.27 (d, J = 7.7 Hz, 1H), 4.05 (d, J = 17.1 Hz, 1H), 3.97−3.80 (m, 2H), 3.05 (d, J = 7.3 Hz, 1H), 2.64 (d, J = 4.6 Hz, 1H), 2.46 (s, 2H); 13C NMR (126 MHz, CD3CN) δ 169.2, 151.7, 143.9, 136.3, 133.5, 130.0, 126.9, 125.3, 5078

DOI: 10.1021/acs.joc.8b00402 J. Org. Chem. 2018, 83, 5072−5081

Article

The Journal of Organic Chemistry hexane/EtOAc (8:2). 1H NMR (400 MHz, CDCl3) δ 8.45−8.32 (m, 1H), 8.25−8.16 (m, 1H), 8.11−8.02 (m, 1H), 7.66 (t, J = 7.5 Hz, 1H), 7.53 (t, J = 7.8 Hz, 1H), 4.32 (dd, J = 7.0, 4.3 Hz, 1H), 3.00 (d, J = 7.0 Hz, 1H), 2.84 (d, J = 4.3 Hz, 1H); 13C NMR (126 MHz, CDCl3) δ 190.5, 150.9, 143.2, 135.3, 134.5, 129.3, 129.0, 128.8, 124.4, 38.0, 33.4; IR (neat) ν 3098 (w), 3029 (w), 2919 (w), 1698 (m), 1523 (m), 1349 (m), 1308 (m), 1163 (s) cm−1; TLC Rf = 0.13 (hexanes/EtOAc, 9:1); HRMS (ESI) m/z: [M + H]+ Calcd for C15H13N2O5S 333.0545; Found 333.0538. (2S,3R)-2-methyl-1-((4-nitrophenyl)sulfonyl)-3-phenylaziridine (3p). Prepared from (Z)-prop-1-en-1-ylbenzene (>5:95 E/Z) and [N(4-nitrobenzenesulfonyl)imino]phenyliodinane following the general procedure for aziridination. The crude product was obtained as a 15:85 (E/Z) mixture of diastereomers. After column chromatography, the product was isolated as a white solid (32 mg, 40% yield, 9:91 (E/Z)) using hexanes/EtOAc (9:1). The characterization data for the compound were in agreement with previously published information.41 1H NMR (400 MHz, CDCl3) δ 8.39 (d, J = 8.8 Hz, 2H), 8.21 (d, J = 8.8 Hz, 2H), 7.34−7.27 (m, 3H), 7.19 (dd, J = 7.4, 2.3 Hz, 2H), 4.07 (d, J = 7.3 Hz, 1H), 3.34 (dq, J = 7.3, 5.8 Hz, 1H), 1.07 (d, J = 5.8 Hz, 3H). (2S,3R)-2-Methyl-1-((4-nitrophenyl)sulfonyl)-3-phenylaziridine (3q). Prepared from (Z)-prop-1-en-1-ylbenzene (>95:5 E/Z) and [N(4-nitrobenzenesulfonyl)imino]phenyliodinane following the general procedure for aziridination. The product was obtained as a white solid (18 mg, 22% yield) in 95:5 (E/Z) after silica gel column chromatography using hexane/EtOAc (9:1). The characterization data for the compound were in agreement with previously published information.41 1H NMR (400 MHz, CDCl3) δ 8.31 (d, J = 8.8 Hz, 2H), 8.11 (d, J = 8.8 Hz, 2H), 7.30−7.26 (m, 3H), 7.13 (dd, J = 6.7, 3.0 Hz, 2H), 3.87 (d, J = 4.4 Hz, 1H), 3.06 (qd, J = 5.9, 4.2 Hz, 1H), 1.88 (d, J = 5.9 Hz, 3H). N4, N4, N4′, N4′-Tetramethyl-[1,1′-biphenyl]-4,4′-diamine (7). Prepared from N,N′-dimethylaniline and [N-(4-nitrobenzenesulfonyl)imino]phenyliodinane after 3 h following the general procedure for aziridination. The product was obtained as a white solid (13.7 mg, 46% yield) after silica gel column chromatography using hexane/EtOAc (98:2). The characterization data for the compound were in agreement with previously published information.42 1H NMR (400 MHz, CDCl3) δ 7.45 (d, J = 8.8 Hz, 4H), 6.80 (d, J = 8.3 Hz, 4H), 2.97 (s, 12H). 2,2,2-Trichloroethyl 2-([1,1′-biphenyl]-4-yl)aziridine-1-sulfonate (11). Prepared from 4-vinylbiphenyl and [N-(2,2,2trichloroethyoxysulfonyl)imino]phenyliodinane following the general procedure for aziridination. The product was obtained as a white solid (28.5 mg, 28% yield) after silica gel column chromatography using hexanes/EtOAc (9:1). 1H NMR (400 MHz, CDCl3) δ 7.62−7.59 (m, 4H), 7.45 (t, J = 7.6 Hz), 7.40−7.37 (m, 3H), 4.88 (ABq, ΔδAB = 0.06, JAB = 10.6 Hz, 2H), 3.92 (dd, J = 7.0 Hz, 4.7 Hz, 2H), 3.13 (d, J = 7.1 Hz, 1H), 2.67 (d, J = 4.7 Hz, 1H); 13C NMR (126 MHz, CDCl3) δ 141.9, 140.2, 132.7, 128.9, 127.7, 127.5, 127.1, 127.0, 92.8, 79.7, 42.6, 37.5; IR (neat) ν 3031 (w), 2955 (w), 1368 (m), 1180 (m) cm−1; TLC Rf = 0.3 (hexanes/EtOAc, 8:2); HRMS (ESI−TOF) m/z: [M + H]+ Calcd for C16H15Cl3NO3S 405.9838; Found 405.9835.

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ORCID

Jennifer L. Roizen: 0000-0002-6053-5512 Author Contributions †

M.F.S. and S.K.A. contributed equally.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This project was funded by the American Chemical Society Petroleum Research Fund Doctoral New Investigator Program (PRF Grant No. 54824-DNI1) and by Duke University. M.F.S. was supported in part by the Kathleen Zielik fellowship. Characterization data were obtained on instrumentation secured by funding from the NSF (Grant CHE-0923097, ESI-MS, George Dubay, the Duke Dept. of Chemistry Instrument Center) or the NSF, the NIH, HHMI, the North Carolina Biotechnology Center, and Duke (Duke Magnetic Resonance Spectroscopy Center).

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.8b00402. Scheme describing the synthesis of ligand, aziridines stability, mass balance for the aziridination reaction is accounted for in part by olefin substrate and aziridine product, HPLC data, and NMR spectra (PDF)

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REFERENCES

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DOI: 10.1021/acs.joc.8b00402 J. Org. Chem. 2018, 83, 5072−5081

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