Reaction of Ynamides with Iminoiodinane-Derived Nitrenes

Orléans, France. J. Org. Chem. , 2017, 82 (22), pp 11897–11902. DOI: 10.1021/acs.joc.7b01623. Publication Date (Web): September 1, 2017. Copyri...
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Cite This: J. Org. Chem. 2017, 82, 11897-11902

Reaction of Ynamides with Iminoiodinane-Derived Nitrenes: Formation of Oxazolones and Polyfunctionalized Oxazolidinones Romain Rey-Rodriguez,† Gwendal Grelier,† Loïc Habert,‡ Pascal Retailleau,† Benjamin Darses,† Isabelle Gillaizeau,*,‡ and Philippe Dauban*,† †

Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Université Paris-Sud, Université Paris-Saclay, Avenue de la terrasse, 91198 Gif-sur-Yvette, France ‡ Institute of Organic and Analytical Chemistry, ICOA UMR 7311 CNRS, Université d’Orléans, rue de Chartres, 45100 Orléans, France S Supporting Information *

ABSTRACT: This article describes the reaction of ynamides with metallanitrenes generated in the presence of an iodine(III) oxidant. N-(Boc)-Ynamides are converted to oxazolones via a cyclization reaction. The reaction is mediated by a catalytic dirhodium-bound nitrene species that first behaves as a Lewis acid. The oxazolones can be converted in a one pot manner to functionalized oxazolidinones following a regio- and stereoselective oxyamination reaction with the same nitrene reagent generated in stoichiometric amounts.

I

Scheme 1. Background for the Study

minoiodinanes PhINR are trivalent iodine reagents, which have been useful for the development of alkene azidination and C(sp3)H amination reactions.1 Their ability to react with a transition metal complex to generate a metallanitrene was first reported by Breslow and Mansuy,2 and then developed by Evans3 and Müller.4 However, their troublesome preparation5 has long hampered their application in organic synthesis. This limitation was overcome with the discovery of practical methods for their in situ generation in the presence of PhIO or PhI(OAc)2.6 The chemistry of iminoiodinanes has considerably expanded since then. Catalytic C(sp3)H amination and alkene aziridination reactions mediated by these iodine(III) oxidants are now methods of choice for the synthesis of nitrogen-containing compounds.1,7 Recent studies with iminoiodinane-derived nitrenes have enabled to extend the scope of the synthetic nitrene chemistry.8 Several efficient alkene difunctionalization9 and cascade10 reactions have been reported in the presence of rhodium, copper, or silver complexes. These synthetic methods generally occur intra- or intermolecularly with excellent regio- and stereocontrol from alkenes, alkynes, or allenes. Our group has contributed to this area with the development of rhodium(II)-catalyzed nitrene additions to indoles,11 enamides,12 and alkenes.13 The combination of trichloroethylsulfamate (TcesNH2) with Rh2(esp)2 (esp = α,α,α′,α′tetramethyl-1,3-benzenedipropionic acid),14 in the presence of PhI(OAc)2 and a nucleophile enabled us to develop efficient regioslective oxyamination and diamination reactions (Scheme 1a). Importantly, we have demonstrated, through a combination of experimental and theoretical studies, that the dirhodium-bound nitrene species not only acts as a nitrogentransfer intermediate, but also possesses a crucial Lewis acidity enabling the aziridine activation toward the nucleophilic ring © 2017 American Chemical Society

opening.13b Based on these results, we have decided to further study the scope of the Lewis acidic property of Rh2(esp)2derived nitrenes. In this article, we wish to report that these species mediate the one pot conversion of ynamides15,16 to oxazolones and, then, to functionalized oxazolidinones (Scheme 1b). Ynamides are useful building blocks in organic synthesis that allow to perform efficient and regioselective transformations.17 These stable compounds are easily prepared by application of copper-catalyzed C−N couplings from alkynyl bromides.18 This Special Issue: Hypervalent Iodine Reagents Received: June 30, 2017 Published: September 1, 2017 11897

DOI: 10.1021/acs.joc.7b01623 J. Org. Chem. 2017, 82, 11897−11902

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The Journal of Organic Chemistry Table 1. Scope of the Cyclization Reactiona

protocol was used for the formation of 1-octyne-derived ynamides that were chosen as model substrates in this study. Application of the previous conditions (1.2 equiv TcesNH2, 1.4 equiv PhI(OAc)2, 3 mol% Rh2(esp)2, 12 equiv MeOH, benzene, rt)12,13 to the benzyl carbamate 1 led to the formation of the oxazolone 3a (Scheme 2). A rapid screening of the Scheme 2. Formation of Oxazolone 2

conditions allowed us to find that the simultaneous presence of the sulfamate, the iodine(III) oxidant, and the rhodium complex was required for the reaction to proceed,19 thereby demonstrating that the Lewis acidic rhodium-bound nitrene species is involved in the cyclization of the ynamide through the activation of the alkyne.20 This hypothesis was confirmed by the fact that the reaction can be performed in the presence of only a catalytic amount of the metallanitrene generated by using 3 mol% of Rh2(esp)2, 10 mol% of TcesNH2 and 10 mol% of PhI(OAc)2. Under these conditions, compound 3a was isolated in 60% yield. More interestingly, application of these conditions to the Boc-ynamide 2a allows for isolation of the same oxazolone 3a in quantitative yield. The reaction is highly chemoselective as no product arising from the possible C(sp3)H amination at the propargylic position is observed.21 This excellent conversion prompted us to study the scope of the cyclization reaction mediated by the rhodium-bound nitrene species. The cyclization was found to proceed efficiently in 2 h at room temperature to afford the expected oxazolones 3 with yields in the 63−99% range (Table 1). The reaction can be applied to Boc-ynamides 2 bearing either an aryl or a benzyl group on the nitrogen, as illustrated by compounds 3a−d. More interestingly, the cyclization tolerates the presence of various functional groups, such as a nonprotected hydroxyl group as in the case of products 3e−g, or a secondary amide (3i).22 This functional group compatibility that has not been reported in previous cyclization reactions catalyzed by gold or palladium complexes,20 has already been noticed in previous reactions involving iminoiodinane-derived nitrenes.1,7 The oxazolone 3j is also a relevant example as it results from a chemoselective reaction of the alkyne in the presence of an alkene. Finally, the conditions nicely apply to an α,ω-bisynamide affording the bis-oxazolone product 3k in quantitative yield. The rhodium-bound nitrene-mediated cyclization of ynamides appeared to us appropriate to design a one-pot protocol with the possible application of the catalytic oxyamidation reaction,12 to oxazolones 3. Thus, after complete conversion of the ynamide to 3a, the addition of 1.1 equiv of TcesNH2, 1.3 equiv of PhI(OAc)2, and 12 equiv of methanol led us to isolate the oxyaminated product 4aa in 30% yield. Running the reaction at 80 °C for 1 h, then, allowed for a slight improvement of the yield, the compound 4aa being obtained in 37% yield (Table 2). Despite the screening of the reaction conditions, this result could not be improved as the product 4aa was shown to decompose in the presence of PhI(OAc)2.23 Nevertheless, we have decided to study the scope of direct conversion of ynamides to the complex oxazolidinones 4 as the

a

Reactions conditions: (Boc)-ynamide 2 (0.2−0.3 mmol), Rh2(esp)2 (3 mol%), TcesNH2 (10 mol%), PhI(OAc)2 (10 mol%), benzene (c = 0.1 M), rt, 2 h.

Table 2. Scope of the Tandem Cyclization−Oxyamination Reactiona

a

Reactions conditions: (Boc)-ynamide 2 (0.2−0.3 mmol), Rh2(esp)2 (3 mol%), TcesNH2 (10 mol%), PhI(OAc)2 (10 mol%), benzene (c = 0.1 M), rt, 2 h, then TcesNH2 (1.1 equiv), PhI(OAc)2 (1.3 equiv), MeOH (12 equiv), 80 °C, 1 h.

latter are stereodefined products that would not be so easily accessible by application of other strategies. The tandem of cyclization-intermolecular oxyamination reactions proceeds with yields in the 37−44% range using alcohols as nucleophiles. The corresponding highly oxidized products 4aa, 4ab, 4ca, 4da, and 4ja were obtained as single 11898

DOI: 10.1021/acs.joc.7b01623 J. Org. Chem. 2017, 82, 11897−11902

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The Journal of Organic Chemistry regioisomers resulting from the formation of a ketal α- to an N,N-aminal. The compatibility of the cyclization reaction with alcohols and amides, then, gave the opportunity to combine this transformation with an intramolecular oxyamination or diamination. Starting from oxazolones 3e, 3g, and 3i, this led us to isolate the sole spiro compounds 4ea, 4ga, and 4ia. The regio- and stereochemistry of the oxyamination reaction were determined by the X-ray structure obtained for the compound 4ga, and NOESY experiments performed from the products 4ab and 4da (see Supporting Information). Thus, these led us to conclude that the oxyamination occurs with a trans stereoselectively, and a regiochemistry that is opposite to that observed with nonsubstituted enamides and benzoxazines.12 This switch in regioselectivity, previously observed with C3-substituted indoles,11 might be attributed to the presence of a substituent at the C-4 position of the oxazolone intermediate that would favor the building of a transient positive charge during the nucleophilic ring opening of a putative aziridine intermediate. Based on the experimental results and the previously reported studies,9,11−13 a proposed mechanism for the tandem cyclization−oxyamidation reactions from ynamides is shown in Scheme 3. A catalytic amount of the Lewis acidic species I,

tandem reaction confirms the possibility to design new reactions in which a metallanitrene can behave as a Lewis acid, thereby extending the scope of reactions involving nitrenes generated in the presence of iodine(III) oxidants.

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EXPERIMENTAL SECTION

Melting points were measured in capillary tubes and were uncorrected. Infrared spectra were recorded on a FT-IR spectrometer. Proton (1H) and carbon (13C) NMR spectra were recorded on 300 and 500 MHz spectrometers (13C, 31P, 19F - probe or Dual 13C probe). Chemical shifts (δ) are reported in parts per million (ppm) with reference to CDCl3 (1H: 7.26; 13C: 77.13). The following abbreviations are used for the proton spectra multiplicities: s: singlet, d: doublet, t: triplet, q: quartet, quint: quintuplet, sept: septuplet, m: multiplet, br: broad. Coupling constants (J) are reported in Hertz (Hz). The multiplicity of carbons was given using 2D spectra (HMQC and HMBC). The HRMS data were measured on MALDI-TOF type of instrument for the high resolution mass spectra (HRMS). Thin-layer chromatography were performed on silica gel 60 F254 on aluminum plates and visualized under a UVP Mineralight UVLS-28 lamp (254 nm). Flash chromatography was performed on silica gel 60 (230−400 mesh). All reagents were obtained from commercial suppliers and were used as received. General Procedure A for the Cyclization Reaction. In a sealable tube flushed with argon was introduced the ynamide (1.0 equiv), TcesNH2 (10 mol%), Rh2(esp)2 (3 mol%), and benzene (c = 0.1 M). PhI(OAc)2 (10 mol%) was added in one portion and the reaction mixture was stirred at room temperature for 2 h. The mixture was then concentrated under reduced pressure. The residue was purified by column chromatography on silica gel. General Procedure B for the Tandem Cyclization−Intermolecular Oxyamidation Reaction. In a sealable tube flushed with argon was introduced the ynamide (1.0 equiv), TcesNH2 (10 mol%), Rh2(esp)2 (3 mol%), and benzene (c = 0.1 M). PhI(OAc)2 (10 mol%) was added in one portion and the reaction mixture was stirred at room temperature for 2 h. TcesNH2 (1.0 equiv), external nucleophile (12.0 equiv), and PhI(OAc)2 (1.0 equiv) were sequentially added to the tube before it was heated at 80 °C for 2 h. The reaction mixture was allowed to cool down to room temperature before it was concentrated under reduced pressure. The residue was purified by column chromatography on silica gel. 3-Benzyl-5-hexyloxazol-2(3H)-one (3a).16 Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (10/90) as eluent gave the desired product (62 mg, 99%) as a white gum. 1H NMR (500 MHz, CDCl3): δ 7.40−7.25 (m, 5H), 6.21 (s, 1H), 4.59 (s, 2H), 2.35 (t, J = 8.9 Hz, 2H), 1.45−1.15 (m, 8H), 0.92 (t, J = 7.3 Hz, 3H). 3-Benzyl-5-phenyloxazol-2(3H)-one (3b).20b Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (10/90) as eluent gave the desired product (70 mg, 82%) as a white solid. 1H NMR (500 MHz, CDCl3): δ 7.54−7.20 (m, 10H), 6.61 (s, 1H), 4.77 (s, 2H). 3,5-Diphenyloxazol-2(3H)-one (3c).16 Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (10/90) as eluent gave the desired product (85 mg, 99%) as a white solid. 1H NMR (500 MHz, CDCl3): δ 7.60− 7.15 (m, 10H), 6.80 (s, 1H). 3-(3,5-Dimethoxyphenyl)-5-hexyloxazol-2(3H)-one (3d). Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (10/90) as eluent gave the desired product (78 mg, 99%) as a white gum; 1H NMR (400 MHz, CDCl3): δ 6.76−6.74 (m, 2H), 6.54 (s, 1H), 6.34 (s, 1H), 3.81 (s, 6H), 2.45 (t, J = 8.2 Hz, 2H), 1.65−1.57 (m, 2H), 1.41−1.26 (m, 6H), 0.90 (t, J = 6.7 Hz, 3H). 13C{1H} NMR (75 MHz, CDCl3): δ 161.3, 153, 141.9, 137.5, 108.9, 99.0, 98.0, 55.5, 31.4, 28.6, 26.4, 25.9, 22.5, 14.0; IR (Neat): ν = 2958, 2934, 1758, 1596, 1478, 1458, 1205, 1186, 1209, 1150, 1132, 1110 cm−1; HRMS (ESI): m/z calculated for C17H24NO4 [M+H]+: 306.1699 found: 306.1700.

Scheme 3. Proposed Mechanism for the Formation of Oxazolidinones

generated by the combination of Rh2(esp)2, TcesNH2, and PhI(OAc)2, will activate the triple bond of ynamide 1. This would promote its cyclization accompanied by the release of isobutene, leading to the formation of the oxazolone 3. The latter, then, would undergo a rhodium-catalyzed nitrene addition to provide an aziridine intermediate II. Following its activation by I,13b the aziridine undergoes a ring opening at the more substituted position, with different nucleophiles, in an inter- or intramolecular manner to afford the oxazolidinone 4. In conclusion, ynamides can be converted in a simple onepot three-step procedure to functionalized oxazolidinones by reaction with iminoiodinane-derived rhodium-bound nitrenes. The overall transformation relies on a tandem process in which the metallanitrene species plays a dual role. It first acts as a Lewis acid to catalyze the cyclization of ynamides to oxazolones. The reaction takes place with yields of up to 99% and displays very good functional group tolerance. Then, the rhodium-bound nitrene can add to the oxazolone in a one pot manner to afford products resulting from a regio- and stereocontrolled alkene difunctionalization reaction. This 11899

DOI: 10.1021/acs.joc.7b01623 J. Org. Chem. 2017, 82, 11897−11902

Note

The Journal of Organic Chemistry 3-Benzyl-5-(3-hydroxypropyl)oxazol-2(3H)-one (3e). Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (50/50) as eluent gave the desired product (34 mg, 99%) as a white gum. 1H NMR (300 MHz, CDCl3) δ 7.40−7.28 (m, 5H), 6.06 (t, J = 1.3 Hz, 1H), 4.68 (s, 2H), 3.67 (t, J = 6.2 Hz, 2H), 2.52−2.45 (m, 2H), 1.84−1.75 (m, 2H). 13 C{1H} NMR (75 MHz, CDCl3): δ 140.3, 135.5, 129.0, 128.3, 127.9, 109.6, 61.5, 47.6, 29.5, 22.4; IR (neat): ν = 3414, 3138, 2929, 1726, 1667, 1443, 1402, 1160, 1056 cm−1; HRMS (ESI): m/z calcd for C13H16NO3 [M+H]+: 234.1125; found: 234.1143. 5-(3-Hydroxypropyl)-3-phenyloxazol-2(3H)-one (3f). Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (60/40) as eluent gave the desired product (38 mg, 88%) as a white solid. mp 89.7−90.6 °C; 1 H NMR (300 MHz, CDCl3) δ 7.58−7.54 (m, 2H), 7.53−7.41 (m, 2H), 7.30−7.25 (m, 1H), 6.64 (t, J = 1.2 Hz, 1H), 3.75 (t, J = 6.1 Hz, 2H), 2.65−2.60 (m, 2H), 1.95−1.83 (m, 2H). 13C{1H} NMR (75 MHz, CDCl3): δ 141.2, 135.7, 129.4, 126.2, 120.7, 109.4, 61.4, 29.5, 22.4; IR (neat): ν = 3394, 3147, 2936, 1727, 1679, 1601, 1505, 1393, 1210, 1140, 1050, 900 cm−1; HRMS (ESI): m/z calcd for C12H14NO3 [M+H]+: 220.0968; found: 220.0964. 3-Benzyl-5-(4-hydroxybutyl)oxazol-2(3H)-one (3g). Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (80/20) as eluent gave the desired product (27 mg, 63%) as a yellow solid. mp 36.8−37.2 °C; 1H NMR (300 MHz, CDCl3) δ 7.38−7.26 (m, 5H), 6.05 (t, J = 1.2 Hz, 1H), 4.67 (s, 2H), 3.63 (t, J = 5.8 Hz, 2H), 2.40 (t, J = 6.8 Hz, 2H), 1.64−1.55 (m, 4H). 13C{1H} NMR (75 MHz, CDCl3): δ 155.9, 140.9, 135.7, 129.1, 128.4, 128.1, 109.5, 62.5, 47.6, 31.9, 25.8, 23.0; IR (neat): ν = 3385, 3130, 3059, 2932, 1723, 1669, 1604, 1495, 1450, 1438, 1407, 1360, 1302, 1182, 1168, 1085, 1052, 1038, 965 cm−1; HRMS (ESI): m/z calcd for C14H18NO3 [M+H]+: 248.1281; found: 248.1268. 5-(3-Chloropropyl)-3-phenyloxazol-2(3H)-one (3h). Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (10/90) as eluent gave the desired product (55 mg, 88%) as a white gum; 1H NMR (400 MHz, CDCl3) δ 7.55 (d, J = 8.0 Hz, 2H), 7.43 (t, J = 7.8 Hz, 2H), 7.26 (t, J = 7.4 Hz, 1H), 6.67 (s, 1H), 3.61 (t, J = 6.1 Hz, 2H), 2.68 (t, J = 7.2 Hz, 2H), 2.13−2.07 (m, 2H). 13C{1H} NMR (75 MHz, CDCl3): δ 153.1, 139.9, 135.6, 129.4, 126.3, 120.7, 110.1, 43.6, 29.3, 23.1; IR (neat): ν = 3145, 2916, 1735, 1675, 1601, 1506, 1400, 1260, 1209, 1135, 975, 757 cm−1; HRMS (ESI): m/z calcd for C12H13NO2Cl [M+H]+: 238.0629 found: 238.0628. N-(3-(3-Benzyl-2-oxo-2,3-dihydrooxazol-5-yl)propyl)-4-methylbenzenesulfonamide (3i). Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (60/40) as eluent gave the desired product (22 mg, 85%) as a colorless oil. 1H NMR (300 MHz, CDCl3) δ 7.73−7.69 (m, 2H), 7.40−7.25 (m, 7H), 6.09 (t, J = 1.2 Hz, 1H), 4.84 (t, J = 6.4 Hz, 1H), 4.67 (s, 2H), 2.94 (d, J = 6.6 Hz, 2H), 2.45−2.39 (m, 5H), 1.76− 1.67 (m, 2H). 13C{1H} NMR (75 MHz, CDCl3): δ 155.6, 143.5, 139.3, 136.8, 135.5, 129.8, 128.9, 128.3, 127.9, 127.0, 110.3, 47.6, 41.9, 26.8, 22.8, 21.5; IR (neat): ν = 3254, 2929, 1731, 1668, 1496, 1441, 1402, 1322, 1304, 1152, 1090, 958 cm−1; HRMS (ESI): m/z calcd for C20H23N2O4S [M+H]+: 387.1373; found: 387.1390. 3-Benzyl-5-(cyclohex-1-en-1-yl)oxazol-2(3H)-one (3j). Prepared according to the general procedure A. Purification on a column of silica gel with ethyl acetate in petroleum ether (15/85) as eluent gave the desired product (70 mg, 85%) as a white solid. mp 128.6−129.6 °C; 1H NMR (300 MHz, CDCl3) δ 7.38−7.27 (m, 5H), 6.17−6.15 (m, 1H), 6.10 (s, 1H), 4.71 (s, 2H), 2.17−2.15 (m, 2H), 2.00−1.98 (m, 2H), 1.67−1.60 (m, 4H). 13C{1H} NMR (75 MHz, CDCl3): δ 135.5, 129.3, 129.0, 128.8, 128.3, 127.9, 124.0, 107.3, 47.7, 25.0, 23.3, 22.0, 21.8; IR (neat): ν = 3134, 3034, 2944, 1738, 1441, 1394, 1352, 1175, 1088, 1010, 845 cm−1; HRMS (ESI): m/z calcd for C16H18NO2 [M+H]+: 256.1332; found: 256.1344. 5,5′-(Propane-1,3-diyl)bis(3-benzyloxazol-2(3H)-one) (3k). Prepared according to the general procedure A. Recrystallization of the crude product in ethyl acetate gave the desired product (76 mg, 99%) as a white solid. mp 163.3−164.5 °C; 1H NMR (300 MHz, CDCl3) δ

7.57−7.53 (m, 4H), 7.47−7.41 (m, 4H), 7.30−7.24 (m, 2H), 6.66 (s, 2H), 2.60 (td, J = 7.3, 1.3 Hz, 4H), 1.99 (p, J = 7.4 Hz, 2H). 13C{1H} NMR (75 MHz, CDCl3): δ 155.9, 140.5, 134.2, 129.4, 126.3, 120.7, 109.8, 25.1, 23.9; IR (neat): ν = 3139, 3049, 2957, 1731, 1674, 1600, 1504, 1397, 1211, 1126, 898 cm−1; HRMS (ESI): m/z calcd for C21H19N2O4 [M+H]+: 363.1340; found: 363.1326. 2,2,2-Trichloroethyl (3-Benzyl-5-hexyl-5-methoxy-2-oxooxazolidin-4-yl)sulfamate (4aa). Prepared according to the general procedure B. Purification on a column of silica gel with ethyl acetate in petroleum ether (10/90) as eluent gave the desired product (33 mg, 37%) as a colorless gum. 1H NMR (300 MHz, CDCl3) δ 7.45−7.31 (m, 5H), 5.22−5.12 (m, 1H), 4.95 (s, 1H), 4.85 (d, J = 15.5 Hz, 1H), 4.78 (d, J = 12.0 Hz, 1H), 4.72−4.69 (m, 1H), 4.37 (d, J = 15.5 Hz, 1H), 3.26 (s, 3H), 2.12−2.04 (m, 1H), 1.98−1.91 (m, 1H), 1.40−1.23 (m, 7H), 0.92−0.85 (m, 4H). 13C{1H} NMR (75 MHz, CDCl3): δ 156.4, 134.8, 128.9, 128.2, 128.1, 107.4, 93.3, 78.7, 72.5, 50.2, 44.8, 31.5, 30.7, 29.3, 22.5, 22.1, 14.0; IR (neat): ν = 3287, 2927, 1741, 1450, 1372, 1187, 1085, 1012, 854 cm−1; HRMS (ESI): m/z calculated for C19H28Cl3N2O6S [M+H]+: 517.0728, found 517.0727. 2,2,2-Trichloroethyl (3-Benzyl-5-ethoxy-5-hexyl-2-oxooxazolidin4-yl)sulfamate (4ab). Prepared according to the general procedure B. Purification on a column of silica gel with ethyl acetate in petroleum ether (10/90) as eluent gave the desired product (28 mg, 39%) as a white solid. mp 87.5−91.8 °C; 1H NMR (300 MHz, CDCl3) δ 7.30− 7.23 (m, 5H), 6.96 (d, J = 9.8 Hz, 1H), 4.83 (d, J = 9.8 Hz, 1H), 4.77 (d, J = 15.5 Hz, 1H), 4.69 (d, J = 11.0 Hz, 1H), 4.62 (d, J = 11.0 Hz, 1H), 4.28 (d, J = 15.5 Hz, 1H), 3.38−3.36 (m, 2H), 2.00−1.94 (m, 1H), 1.88−1.82 (m, 1H), 1.45−1.39 (m, 1H), 1.30−1.15 (m, 7H), 1.03 (t, J = 6.9 Hz, 3H), 0.79 (t, J = 6.8 Hz, 3H). 13C{1H} NMR (75 MHz, CDCl3): δ 156.7, 135, 129, 128.3, 128.1, 107.4, 93.5, 78.8, 72.8, 58.5, 44.9, 31.6, 31, 29.4, 22.7, 22.3, 15.3, 14.2; IR (neat): ν = 3150, 2929, 1746, 1450, 1422, 1392, 1320, 1221, 1186, 1085, 1006, 958, 855 cm−1; HRMS (ESI): m/z calcd for C20H30Cl3N2O6S [M+H]+: 531.0885; found: 531.0917. 2,2,2-Trichloroethyl (5-Methoxy-2-oxo-3,5-diphenyloxazolidin-4yl)sulfamate (4ca). Prepared according to the general procedure B. Purification on a column of silica gel with ethyl acetate in petroleum ether (10/90) as eluent gave the desired product (21 mg, 42%) as a brownish solid with remaining traces of NH2Tces. mp 168−169.4 °C; 1 H NMR (300 MHz, CDCl3) δ 7.63−7.60 (m, 2H), 7.56−7.51 (m, 5H), 7.44 (t, J = 7.7 Hz, 2H), 7.32 (t, J = 7.6 Hz, 1H), 5.82−5.80 (m, 1H), 5.09−5.07 (m, 1H), 4.69−4.68 (m, 1H), 3.80−3.73 (m, 2H), 3.34 (s, 3H). 13C{1H} NMR (75 MHz, CDCl3): δ 153.2, 134.5, 131.6, 130.6, 129.6, 129.4, 127.5, 124.4, 107, 92.8, 77.9, 76.4, 52.1; IR (neat): ν = 3169, 2989, 2947, 1758, 1742, 1599, 1505, 1452, 1418, 1390, 1368, 1230, 1168, 1116, 1083, 998, 943 cm−1; HRMS (ESI): m/z calculated for C18H18Cl3N2O6S [M+H]+: 494.9945, found 494.9943. 2,2,2-Trichloroethyl (3-(3,5-Dimethoxyphenyl)-5-hexyl-5-methoxy-2-oxooxazolidin-4-yl)sulfamate (4da). Prepared according to the general procedure B. Purification on a column of silica gel with ethyl acetate in petroleum ether (20/80) as eluent gave the desired product (33 mg, 38%) as a brown oil contamiated with remaining traces of NH2Tces. 1H NMR (300 MHz, CDCl3) δ 6.69−6.68 (m, 2H), 6.37−6.35 (m, 2H), 5.52 (d, J = 9.8 Hz, 1H), 4.26 (d, J = 11.0 Hz, 1H), 4.06 (d, J = 11.0 Hz, 1H), 3.78 (s, 6H), 3.44 (s, 3H), 2.18− 2.08 (m, 1H), 1.95−1.88 (m, 1H), 1.39−1.15 (m, 7H), 0.95−0.85 (m, 4H). 13C{1H} NMR (75 MHz, CDCl3): δ 161.4, 153.8, 136.2, 106.8, 102.2, 99.4, 93.0, 78.5, 74.8, 55.5, 50.5, 31.5, 30.1, 29.3, 22.5, 22.0, 14.0; IR (neat): ν = 3285, 2955, 1749, 1598, 1451, 1368, 1182, 1086, 1012, 926 cm−1.; HRMS (ESI): m/z calculated for C20H30Cl3N2O8S [M+H]+: 563.0782, found 563.0783. 2,2,2-Trichloroethyl (3-Benzyl-5-(cyclohex-1-en-1-yl)-5-methoxy2-oxooxazolidin-4-yl)sulfamate (4ja). Prepared according to the general procedure B. Purification on a column of silica gel with ethyl acetate in petroleum ether (15/85) as eluent gave the desired product (69 mg, 44%) as a colorless gum. 1H NMR (300 MHz, CDCl3) δ 7.39−7.30 (m, 5H), 6.34−6.30 (m, 1H), 5.55 (d, J = 9.5 Hz, 1H), 4.96−4.88 (m, 2H), 4.65−4.63 (m, 2H), 4.35 (d, J = 15.7 Hz, 1H), 3.27 (s, 3H), 2.14−2.21 (m, 2H), 2.09−2.00 (m, 1H), 1.91−1.84 (m, 1H), 1.70−1.56 (m, 4H). 13C{1H} NMR (75 MHz, CDCl3): δ 155.3, 11900

DOI: 10.1021/acs.joc.7b01623 J. Org. Chem. 2017, 82, 11897−11902

The Journal of Organic Chemistry 135.1, 131.8, 129.7, 128.8, 128.0, 127.9, 107.1, 93.2, 78.5, 72.2, 51.1, 45.0, 25.0, 24.0, 22.1, 21.7; IR (neat): ν = 2937, 1745, 1456, 1429, 1384, 1187, 1088, 1007, 981, 858 cm−1; HRMS (ESI): m/z calcd for C19H24Cl3N2O6S [M+H]+: 513.0415; found: 513.0439. 2,2,2-Trichloroethyl (3-Benzyl-2-oxo-1,6-dioxa-3-azaspiro[4.4]nonan-4-yl)sulfamate (4ea). Prepared according to the general procedure B. Purification on a column of silica gel with ethyl acetate in petroleum ether (30/70) as eluent gave the desired product (25 mg, 35%) as a yellow gum. 1H NMR (300 MHz, CDCl3) δ 7.38−7.30 (m, 5H), 7.23 (d, J = 9.8 Hz, 1H), 5.03 (d, J = 9.8 Hz, 1H), 4.82 (d, J = 16.1 Hz, 1H), 4.69 (d, J = 11.2 Hz, 1H), 4.63 (d, J = 11.2 Hz, 1H), 4.30 (d, J = 16.1 Hz, 1H), 4.21−4.17 (m, 1H), 4.05 (q, J = 7.9 Hz, 1H), 2.42−2.34 (m, 2H), 2.22−2.14 (m, 1H), 2.12−2.04 (m, 1H). 13 C{1H} NMR (75 MHz, CDCl3): δ 155.5, 134.9, 129.1, 128.3, 128.1, 113.1, 93.5, 78.6, 72.4, 70.4, 44.9, 32.2, 23.3; IR (neat): ν = 3204, 2903, 1737, 1443, 1418, 1365, 1331, 1263, 1228, 1211, 1171, 1070, 1015, 949, 847 cm−1; HRMS (ESI): m/z calcd for C15H18Cl3N2O6S [M+H]+: 458.9946; found: 458.9944. 2,2,2-Trichloroethyl (3-Benzyl-2-oxo-1,6-dioxa-3-azaspiro[4.5]decan-4-yl)sulfamate (4ga). Prepared according to the general procedure B. Purification on a column of silica gel with ethyl acetate in petroleum ether (15/85) as eluent gave the desired product (35 mg, 23%) as a white solid. Mp 158.1−161.9 °C; 1H NMR (300 MHz, CDCl3) δ 7.37−7.30 (m, 5H), 6.86−6.79 (m, 1H), 4.84−4.77 (m, 2H), 4.69 (d, J = 11.0 Hz, 1H), 4.61 (d, J = 11 Hz, 1H), 4.32 (d, J = 15.6 Hz, 1H), 4.04−3.95 (m, 1H), 3.83−3.79 (m, 1H), 2.10−2.04 (m, 1H), 1.96−1.89 (m, 3H), 1.69−1.64 (m, 2H). 13C{1H} NMR (75 MHz, CDCl3): δ 156.3, 134.8, 128.9, 128.1, 127.9, 104.0, 93.3, 78.5, 74.0, 63.9, 44.8, 28.7, 24.1, 18.7; IR (neat): ν = 3134, 1741, 1483, 1434, 1365, 1245, 1183, 1081, 1012, 976, 939, 871, 850 cm−1; HRMS (ESI): m/z calcd for C16H20Cl3N2O6S [M+H]+: 473.0102; found: 473.0100. 2,2,2-Trichloroethyl (3-Benzyl-2-oxo-6-tosyl-1-oxa-3,6diazaspiro[4.4]nonan-4-yl)sulfamate (4ia). Prepared according to the general procedure B. Purification on a column of silica gel with ethyl acetate in petroleum ether (30/70) as eluent gave the desired product (19 mg, 19%) as a brown solid. Mp 80.5−80.7 °C; 1H NMR (300 MHz, CDCl3) δ 7.66−7.64 (m, 2H), 7.53−7.50 (m, 2H), 7.38− 7.29 (m, 5H), 6.00−5.92 (m, 1H), 5.83−5.75 (m, 1H), 4.67 (d, J = 15.2 Hz, 1H), 4.63−4.54 (m, 2H), 4.53 (d, J = 15.2 Hz, 1H), 3.51− 3.38 (m, 2H), 2.62−2.51 (m, 1H), 2.42 (s, 3H), 2.08−2.15 (m, 1H), 1.94−1.83 (m, 2H). 13C{1H} NMR (75 MHz, CDCl3): δ 154.9, 144.5, 135.6, 130.0, 129.9, 129.2, 129.0, 128.4, 128.1, 100.1, 99.6, 78.4, 75.0, 50.0, 47.3, 36.5, 21.9, 21.7; R (neat): ν = 2923, 1747, 1597, 1443, 1348, 1250, 1186, 1158, 1082, 1054, 1001, 966, 851 cm−1; HRMS (ESI): m/z calcd for C22H25Cl3N3O7S2 [M+H]+: 612. 0121; found: 611.0121.

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ACKNOWLEDGMENTS

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REFERENCES

We wish to thank the French National Research Agency (program n° ANR-11-IDEX-0003-02, CHARMMMAT ANR11-LABX-0039, program n° ANR-15-CE29-0014-01; fellowship to R.R.-R.), the Ministère de l′Enseignement Supérieur et de la Recherche (fellowship to G.G.), the Region Centre Val de Loire (fellowship to L.H.), and the Institut de Chimie des Substances Naturelles for their support.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b01623. X-ray crystallographic data of compound 4ga (CIF) General notes and general procedures and 1H and 13C NMR spectra of compounds 2a, 2d−k, 3d−k, and 4 (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*[email protected] *[email protected] ORCID

Isabelle Gillaizeau: 0000-0002-7726-3592 Philippe Dauban: 0000-0002-1048-5529 Notes

The authors declare no competing financial interest. 11901

DOI: 10.1021/acs.joc.7b01623 J. Org. Chem. 2017, 82, 11897−11902

Note

The Journal of Organic Chemistry (14) (a) Guthikonda, K.; Du Bois, J. J. Am. Chem. Soc. 2002, 124, 13672. (b) Espino, C. G.; Fiori, K. W.; Kim, M.; Du Bois, J. J. Am. Chem. Soc. 2004, 126, 15378. (15) For gold-catalyzed additions of nitrene equivalents to ynamides, see: (a) Li, C.; Zhang, L. Org. Lett. 2011, 13, 1738. (b) Davies, P. W.; Cremonesi, A.; Dumitrescu, L. Angew. Chem., Int. Ed. 2011, 50, 8931. (16) For recent studies on ynamides from one of us, see: Sallio, R.; Corpet, M.; Habert, L.; Durandetti, M.; Gosmini, C.; Gillaizeau, I. J. Org. Chem. 2017, 82, 1254. (17) (a) Zificsak, C. A.; Mulder, J. A.; Hsung, R. P.; Rameshkumar, C.; Wei, L.-L. Tetrahedron 2001, 57, 7575. (b) Evano, G.; Coste, A.; Jouvin, K. Angew. Chem., Int. Ed. 2010, 49, 2840. (18) Zhang, X.; Zhang, Y.; Huang, J.; Hsung, R. P.; Kurtz, K. C. M.; Oppenheimer, J.; Petersen, M. E.; Sagamanova, I. K.; Shen, L.; Tracey, M. R. J. Org. Chem. 2006, 71, 4170. (19) We have performed several test experiments using only Rh2(esp)2, or only PhI(OAc)2, or involving a combination of PhI(OAc)2 and Rh2(esp)2, or of TcesNH2 and Rh2(esp)2. In each case, we did not observe the formation of the oxazolone. These results support the hypothesis that the dirhodium-nitrene complex promotes the cyclization reaction. AcOH could also potentially mediate the reaction as it is released from PhI(OAc)2 during the formation of the iminoiodinane. However, we have also checked that the cyclization does not proceed in the presence of AcOH. (20) For previous reports on the catalytic cycloisomerization of ynamides, see: (a) Hashmi, A. S. K.; Salathé, R.; Frey, W. Synlett 2007, 2007, 1763. (b) Istrate, F. M.; Buzas, A. K.; Jurberg, I. D.; Odabachian, Y.; Gagosz, F. Org. Lett. 2008, 10, 925. (c) Lu, Z.; Xu, X.; Yang, Z.; Kong, Y.; Zhu, G. Tetrahedron Lett. 2012, 53, 3433. (d) Lu, Z.; Cui, W.; Xia, S.; Bai, Y.; Luo, F.; Zhu, G. J. Org. Chem. 2012, 77, 9871. (e) Huang, H.; Zhu, X.; He, G.; Liu, Q.; Fan, J.; Zhu, H. Org. Lett. 2015, 17, 2510. (f) Huang, H.; He, G.; Zhu, G.; Zhu, X.; Qiu, S.; Zhu, H. J. Org. Chem. 2015, 80, 3480. (g) Tang, L.; Huang, H.; Xi, Y.; He, G.; Zhu, H. Org. Biomol. Chem. 2017, 15, 2923. (21) For recent examples of catalytic propargylic C(sp3)−H amination, see: (a) Grigg, R. D.; Rigoli, J. W.; Pearce, S. D.; Schomaker, J. M. Org. Lett. 2012, 14, 280. (b) Lebel, H.; Trudel, C.; Spitz, C. Chem. Commun. 2012, 48, 7799. (22) Screening of the solvents (CH2Cl2, (CHCl2)2, CF3CH2OH) and the iodine oxidant (PhI(OPiv)2) has been made with ynamide 3e to improve the yields albeit without success. (23) The direct reaction of ynamide 3a in the presence of 3 mol% of Rh2(esp)2, 1.2 equiv of TcesNH2, 1.4 equiv of PhI(OAc)2, and 12 equiv of methanol, was also performed but compound 4aa was isolated with a lower yield because of its extensive decomposition. For a previous example of the decomposition of oxazolone under oxidative conditions, see: Sheehan, J. C.; Guziec, F. S., Jr. J. Am. Chem. Soc. 1972, 94, 6561.

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DOI: 10.1021/acs.joc.7b01623 J. Org. Chem. 2017, 82, 11897−11902