Direct and Catalytic Amide Synthesis from Ketones via Transoximation

Oct 15, 2018 - Kengo Hyodo* , Genna Hasegawa , Naoki Oishi , Kazuma Kuroda , and Kingo Uchida. Department of Material Chemistry, Faculty of Science ...
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Cite This: J. Org. Chem. 2018, 83, 13080−13087

Direct and Catalytic Amide Synthesis from Ketones via Transoximation and Beckmann Rearrangement under Mild Conditions Kengo Hyodo,* Genna Hasegawa, Naoki Oishi, Kazuma Kuroda, and Kingo Uchida

J. Org. Chem. 2018.83:13080-13087. Downloaded from pubs.acs.org by UNIV OF ALABAMA BIRMINGHAM on 01/03/19. For personal use only.

Department of Material Chemistry, Faculty of Science and Technology, Ryukoku University, Seta, Otsu, Shiga 520-2194, Japan S Supporting Information *

ABSTRACT: The Brønsted acid-catalyzed synthesis of secondary amides from ketones under mild conditions is described via transoximation and Beckmann rearrangement using O-protected oximes as more stable equivalents of explosive O-protected hydroxylamines. This methodology could be applied to highly rearrangement-selective amide synthesis from α-branched alkyl aryl ketones and performed on a 1-g scale. The presence of water is essential for this reaction, and its role was clarified by isotope-labeling experiments.

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INTRODUCTION Secondary amides are important functional groups found in pharmaceuticals, natural products, and textiles (Figure 1).1 To

Scheme 1. Beckmann Rearrangement from Ketoximes and Ketones

Figure 1. Key compounds containing secondary amide structures.

date, several methods for amide synthesis have been developed, e.g., condensation reactions of primary amines with acid chlorides, esters, carboxylic acids, and aldehydes, etc.2,3 The Beckmann rearrangement from ketoximes is a wellknown reaction for lactam synthesis and is extremely versatile for the industrial manufacture of nylon-6.4 In the typical method, a stoichiometric amount of strong acid is required at high temperature (Scheme 1A). Recently, the reaction under milder conditions has been achieved using an organocatalyst and Lewis acid: cyanuric acid,5 1,3,5-triazo-2,4,6-triphosphorine-2,2,4,4,6,6-chloride (TAPC),6 TsCl,7 cyclopropenium,8 Ca(NTf2)2,9 boronic acid,10 etc.11 On the other hand, direct amide synthesis via Beckmann rearrangement from a ketone, which is a ketoxime precursor, could be regarded as a formal NH insertion reaction next to the carbonyl carbon of the ketone, and would be an attractive method to eliminate both the preparation and tedious purification of oxime isomers.12,13 As the main reaction partner for the ketones, hydroxylamine salts (Scheme 1B(a))14 and O-(mesitylsulfonyl)hydroxylamine (MSH reagent, Scheme 1B(b))15 have been reported.16 However, hydroxylamine is explosive and unstable at high © 2018 American Chemical Society

temperature and must be used under harsh reaction conditions. While MSH reagent can be used under mild conditions, Al2O3/MeOH is required for the subsequent transformation to the amide after formation of the intermediate O-mesitylenesulfonyl ketoxime. Additionally, MSH is explosive and must be handled carefully.17 Received: July 15, 2018 Published: October 15, 2018 13080

DOI: 10.1021/acs.joc.8b01810 J. Org. Chem. 2018, 83, 13080−13087

Article

The Journal of Organic Chemistry The transoximation reaction can be used with more stable oximes instead of unstable hydroxylamine and its derivatives.18 We previously reported Brønsted acid-catalyzed nitrile synthesis using this concept, which demonstrated that an oxime reagent having an electron-withdrawing group on the hydroxyl group acted as a hydroxylamine derivative.19 Herein we attempted direct and catalytic amide synthesis from ketones via transoximation and Beckmann rearrangement using a benchstable oxime reagent as an equivalent of a MSH reagent (Scheme 1B(c)). This achievement under mild conditions would be practical for oximes that undergo isomerization under harsh reaction conditions or when isolation of geometric isomers is difficult. For example, when E/Z mixtures of isobutyrophenone oximes were used in the Beckmann rearrangement, the reaction gave both phenyl-migrated and isopropyl-migrated amides in a ratio similar to the isomeric ratio of the ketoximes (Scheme 2(a)).5

Table 1. Optimization of Reaction Conditions for Amide Synthesisa

Scheme 2. Chemoselective Beckmann Rearrangement from Ketoximes

entry

2

H2O X (equiv)

time (h)

yield (%)b

1 2 3 4c 5 6 7 8d 9e

2a 2a 2a 2a 2b 2c 2d 2a 2a

0 0.5 1.05 1.05 1.05 1.05 1.05 1.05 1.05

24 24 8 24 36 24 24 8 24

8 49 90 0 95 0 0 91 90

a Reaction conditions: 1a (0.50 mmol), 2 (1.2 equiv), TsOH·H2O (5 mol %) in CH3CN (1.0 M) at rt. bIsolated yield. cThis reaction was performed without TsOH·H2O. dTsOH·H2O was loading 2.5 mol %. e TsOH·H2O was loading 0.5 mol %.

was obtained (entry 1). Interestingly as the loading amount of water was increased, the yield of the amide improved (entries 1−3). The reaction did not proceed at all in the absence of catalyst (entry 4). We also investigated the effect of protecting groups of oxime reagent 2. The sulfonyl group was suitable for the reaction, but the methanesulfonyl group required a longer reaction time of 36 h to reach a high yield (entry 5). Oximes having acetyl or benzoyl groups were less reactive and stopped after the transoximation step, giving the corresponding Oprotected oximes without undergoing the Beckmann rearrangement (entries 6, 7). The amount of catalyst loaded could be reduced to 2.5 mol % while maintaining good performance and could be further reduced to a minimum of 0.5 mol % by prolonging the reaction time. Having optimized the reaction conditions, we investigated the scope of various ketone substrates (Table 2). The reactions of some acetophenones such as methyl aryl ketones and those having electron-donating groups on the aromatic ring proceeded at room temperature (3a−h). The halogenated or 4-methyl ester aryl methyl ketones underwent the reaction at 40 °C (3i, 3j, 3k, 3n), and those with electron-withdrawing groups such as nitro and cyano groups gave the corresponding amides at elevated temperature (3l, 3m). Heteroaryl methyl ketones also afforded the amides 3o and 3p at moderate yields. The aryl aryl ketone and alkyl methyl ketone afforded the corresponding amides (3q−s). Importantly, cyclic ketones showed good reactivity and transformed directly to the corresponding lactams at 40 °C (3t−v). As an example of a late stage functionalization of a commercial product, Celestolide 1w, which is a perfume, underwent transoximation/Beckmann rearrangement in high yield (3w). This wide range of substrates encouraged us to attempt the reaction of oxime 2 with ketones that could form two kinds of amides by the migration selectivity of the Beckmann rearrangement (Table 3). Propiophenone 1x was converted to amide 3x in which the benzene ring migrated to the nitrogen atom with good selectivity, although in the case of isobutyrophenone 1y, the aryl-migration selectivity was lower

However, very recently, D. G. Hall and co-workers achieved the synthesis of amide 3y with good chemoselectivity (3y/4y = 83/17) from 1:1 mixtures of isobutyrophenone oxime isomers at room temperature (Scheme 2(b)).10 Moreover, D. Y. Chi and co-workers reported that the reaction using a single isomer of 1-indanone oxime tosylate at low temperature gave a single corresponding amide from the ketoxime while retaining the geometry (Scheme 2(c)).12 Therefore, these pioneering examples using ketoximes encouraged us to attempt to develop a chemoselective amide synthesis by a selective NH insertion reaction to an unsymmetrical ketone under mild conditions (Scheme 2(d)).

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RESULTS AND DISCUSSION We optimized the reaction conditions for the amide synthesis using 2′-acetonaphthone 1a and oxime 2 with TsOH·H2O as a catalyst in CH3CN at room temperature (Table 1).20 In the absence of water as an additive, only a trace amount of amide 13081

DOI: 10.1021/acs.joc.8b01810 J. Org. Chem. 2018, 83, 13080−13087

Article

The Journal of Organic Chemistry Table 2. Scope of Various Ketonesa,b

This strategy for preparing lactams via transoximation and Beckmann rearrangement was applied to the large scale synthesis of a breast cancer drug precursor (Scheme 3(a)).22 Scheme 3. Synthetic Applications. (a) Gram-Scale Synthesis of Bioactive Compound. (b) Simultaneous Transformation of Both Aldehyde and Ketone Functional Groups

a Reaction conditions: 1 (0.50 mmol), 2a (1.2 equiv), TsOH·H2O (2.5 mol %) in CH3CN (1.0 M) at rt. bIsolated yield. cThis reaction was performed at 40 °C. dThis reaction was performed under reflux.

Table 3. Scope of Various Ketonesa,b,c The starting cyclic ketone 5 was reacted with oxime 2a at ambient temperature, after which the obtained lactam was deacetylated to afford estrone lactam 6 (0.75 g, 55%). The lactam was then converted to the target compound 7 using sulfamoyl chloride. As another application of this lactam synthesis, when 4-formylacetopheneone 8 was reacted with 2.4 equiv of 2a at reflux, two different functional groups, the acetyl and formyl groups, were simultaneously transformed into amide and cyano groups, respectively (Scheme 3(b)). We observed the course of the reaction of 1a and 2b catalyzed by TsOH·H2O by 1H NMR spectroscopy in CH3CN (Figure 2). As soon as the reaction started, E and Z O-Ms ketoximes 9a were observed and amide 3a was generated after 4 h. The ketone 1a was completely consumed within 21 h, and almost all of the oxime intermediate 9a disappeared after 36 h.

a

Reaction conditions: 1 (0.50 mmol), 2b (1.2 equiv), TsOH·H2O (2.5 mol %) in CH3CN (1.0 M). bThe ratio of two kinds of amides was determined by 1H NMR from crude mixtures. cIsolated yield of the major amide product. d30 mol % of TsOH·H2O was used. e2a was used instead of 2b. f Ethyl (2, 4-dinitrobenzenesulfonyl)acetohydroxymate (2e) was used instead of 2b.

at room temperature.21 The ratio of phenyl migration product 3y was improved by decreasing the reaction temperature. Similarly, cyclopropyl phenyl ketone 1z and cyclohexyl phenyl ketone 1aa gave the corresponding phenyl-migrated products 3z and 3aa with good chemoselectivity. Unfortunately, the aryl aryl ketone, 4-methoxyphenyl phenyl ketone 1ab, was not selective, resulting in a mixture of amides 3ab and 4ab in a ratio of 57:43. α-Tetralone gave 3ac in high selectivity by using 2e at reflux. 2-Methylcyclohexanone 1ad, α-branched cyclic ketone, gave branched alkyl chain-migrated product 3ad with good chemoselectivity. We hypothesized the reason for the origin of the selectivity as follows (Figures S9, S10). After oxime intermediates were formed as E/Z mixtures via transoximation, one isomer preferentially underwent the Beckmann rearrangement to the corresponding amide, while the other isomer underwent geometric isomerization under the acidic reaction conditions.

Figure 2. Reaction behavior in situ between 1a and 2b. 13082

DOI: 10.1021/acs.joc.8b01810 J. Org. Chem. 2018, 83, 13080−13087

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The Journal of Organic Chemistry The reaction was cascade-type because formation of the amide occurred in situ.23 To investigate the role of water, which is essential for this reaction to occur, we performed the amide synthesis using 18Olabeled water, H218O (Table 4). The molecular weight of the Table 4. Isotope Experiments Using 18O-Labeled Reagents

3a entry

1aa x

2ab y

H2Oc z

yield (%)d

1 2 3 4

16 16 18 18

16 18 16 16

18 16 16 18

99 98 90 99

O/(16O+18O) (%)e

18

Figure 3. Proposed reaction path.

53 1 50 89

catalyzed by TsOH·H2O under mild conditions, enabling the use of O-protected oximes in place of hydroxylamine salt or MSH reagent. The reaction conditions were not only tolerated by various ketones and gave the desired amides in good yields but also gave selective amide-migrated aromatic groups from α-branched alkyl aryl ketones. The reaction could be conducted on a 1-g scale. We clarified that water was required to promote the reaction and that 0.5 equiv of the added water was consumed to form the carbonyl group of the amide product by isotope-labeling experiments.

a18

O-1a was used 93% 18O-labeled reagents. b18O-2a was used 56% O-labeled reagents. c18O-H2O was used 99% 18O-labeled reagents. d Isolated yield. e18O-Labeled ratio of 3a was determined by ESI-MS. 18

obtained amide was measured by ESI-MS, which showed that 53% 18O-labeled amide was obtained (entry 1). Mysteriously, this result implied that only 0.5 equiv of the 18O atom in the 1.05 equiv of 18O-labeled water was incorporated into the amide. In general, the Beckmann rearrangement using an unprotected ketoxime as a substrate does not require water as an additive because the oxygen of the carbonyl group in the resulting amide is derived from the oxygen in the ketoxime.24 Hence, 18O-labeled oxime 2a was used in the reaction, but most of the resulting amide was not labeled by 18O (entry 2). On the basis of this result, we assumed that water reacted with intermediates formed in the Beckmann rearrangement such as an imide to generate the amide. Next, the use of 18O-labeled ketone 1a gave 50% of 18O-labeled amide (entry 3). This was considered to be due to H218O generated from dehydration/ condensation with the ketone in the transoximation process. Moreover, the use of both 18O-labeled ketone and H218O resulted in 89% 18O incorporation into the amide (entry 4). Therefore, these experiments indicated that the carbonyl oxygen of the amide was derived from the oxygen atoms of both the ketone and water. The water in the transoximation/ Beckmann rearrangement takes part in the formation of the amide after the Beckmann rearrangement. These findings led us to propose a reaction path for the amide synthesis via transoximation/Beckmann rearrangement (Figure 3). Oxime 2a is activated by a Brønsted acid (A) in the presence of water, which then generates NH2OSO2Ph (B) with ethyl acetate. Next, complex B is dehydro-condensed with ketone 1 to provide ketoxime C and water. Complex C is transformed into complex D via Beckmann rearrangement, which then reacts with water and is converted to amide 3 through tautomerization, accompanied by the generation of benzenesulfonic acid. Therefore, the first loaded catalyst probably worked as an initiator. The reprotonation of 2 by p-toluenesulfonic acid or benzenesulfonic acid provides complex A again.

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EXPERIMENTAL SECTION

General Methods. All reactions were performed in oven-dried glassware under a positive pressure of argon. Solvents were transferred via syringe and were introduced into the reaction vessels through a rubber septum. All reactions were monitored by thin-layer chromatography (TLC) carried out on 0.25 mm Merck silica-gel (60-F254). The TLC plates were visualized with UV light and basic KMnO4 with H2O/heat. Column chromatography was carried out on a column packed with silica-gel 60N (spherical neutral size, 40−50 μm). 1H NMR (400 MHz), 19F NMR (376 MHz), and 13C NMR (100 MHz) spectra were measured in CDCl3, (CD3)2CO, CD3CN, or d6-DMSO on a JEOL Resonance JNM-ECS-400. Chemical shifts (δ) are expressed in ppm downfield from internal TMS or CHCl3 or (CH3)2CO or CH3CN or DMSO or C6F6). ESI-MS were recorded on a Agilent G1956B LCMS system with 1100 Series HPLC. Infrared spectra were recorded on a JASCO FT/IR-660 Plus. CH3CN was used after distillation from CaH2. All ketones 1a−z, 1aa−ad, 5, and 8 are commercially available. Oxime 2a−e was prepared following previous reports.19 H218O used was 99% 18O-labeled water made by Taiyo Nippon Sanso Corporation. Most of the amides were characterized by 1H NMR for comparison to previous reports.5,7,8,10,19,22,25−41 General Procedure for O-Protected Oxime Synthesis. The corresponding sulfonyl chloride (1.35 equiv) was added to a solution of ethyl acetohydroxamate (1.0 equiv), triethylamine (1.45 equiv), and DMAP (0.30 equiv) in THF (0.30 M) with stirring under ice cooling. After addition was complete, the reaction mixture was stirred for 6 h at room temperature. Then saturated NH4Cl aq (3 mL) was added to quench the reaction, THF was removed by evaporation, and the remaining aqueous layer was extracted with Et2O (10 mL × 3). The combined organic layer was washed with brine (10 mL) and dried over MgSO4. After removal of MgSO4 from the organic layer, solvent was evaporated under reduced pressure. The remaining crude mixtures were purified by silica gel column chromatography (hexane/ ethyl acetate = 90/10), and a yellow solid product was obtained. Ethyl O-Benzoyl Acetohydroxamate (2c).25 White solid (2.41 mmol scale, 455 mg, 91%). 1H NMR (400 MHz, CDCl3) δ 8.06 (d, J = 8.2 Hz, 2H), 7.58 (t, J = 8.2 Hz, 1H), 7.46 (t, J = 7.3 Hz, 1H), 4.29 (q, J = 7.1 Hz, 2H), 2.16 (s, 3H), 1.36 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, CDCl3, ppm) δ 169.5, 163.9, 133.1, 129.4, 129.3, 128.5,

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CONCLUSIONS We synthesized secondary amides including lactams directly from ketones via the transoximation/Beckmann rearrangement 13083

DOI: 10.1021/acs.joc.8b01810 J. Org. Chem. 2018, 83, 13080−13087

Article

The Journal of Organic Chemistry 63.8, 15.1, 14.2; MS (ESI, positive) m/z calcd C11H14NO3+ [M + H]: 208.10, found 208.10. Ethyl O-Acetyl Acetohydroxamate (2d).25 Colorless liquid (29.0 mmol scale, 3.86 g, 92%). 1H NMR (CDCl3, 400 MHz, ppm) δ 4.19 (q, J = 7.1, 2H), 2.15 (s, 3H), 2.04 (s, 3H), 1.32 (t, J = 7.1, 3H); 13C NMR (100 MHz, CDCl3, ppm) δ 168.8, 168.5, 63.6, 19.6, 14.9, 14.2; MS (ESI, positive) m/z calcd C6H12NO3+ [M + H]: 146.07, found 146.10. Ethyl O-(2,4-Dinitrobenzenesulfonyl)acetohydroxamate (2e). White solid (4.85 mmol scale, 1.22 g, 75%). 1H NMR (CDCl3, 400 MHz, ppm) δ 8.60−8.56 (m, 2H), 8.39 (d, J = 9.0 Hz, 1H), 3.96 (q, J = 7.1 Hz, 2H), 2.15 (s, 3H), 1.25 (t, J = 7.1 Hz, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 172.0, 150.7, 149.1, 134.6, 134.0, 126.1, 120.1, 64.5, 15.5, 14.1; MS (ESI, positive) m/z calcd for C10H12N3O8S+ [M + H]: 334.03, found 334.00.IR (neat) 3112, 1630, 1403, 1108, 1051, 958, 888, 813, 788, 635, 582 cm−1. Anal. Calcd for C10H11N3O8S: C, 36.04; H, 3.33; N, 12.61; found C, 35.87; H, 3.27; N, 12.56. General Procedure for Amide Synthesis from Ketone. To a test tube were added ketone (0.500 mmol, 1.0 equiv), oxime 2a (0.600 mmol, 1.2 equiv), and CH3CN (0.50 mL, 1.0 M) under N2 at room temperature (≈23 °C). Then H2O (0.525 mmol, 1.05 equiv) and TsOH·H2O (0.0125 mmol, 2.5 mol %) were added to the stirred reaction mixture at the indicated temperature. After 24 h, the reaction mixture was quenched by sat. NaHCO3 aq (3 mL) and extracted with ethyl acetate (10 mL × 3). The combined organic phase was washed with brine and dried over Na2SO4. The collected solution was evaporated under reduced pressure, and the remaining crude mixture was purified by silica gel column chromatography (hexane/ethyl acetate = 80/20 to 60/40 to 20/80). N-(2-Naphthyl)acetamide (3a).26 White solid (84.2 mg, 91%). 1H NMR (CDCl3, 400 MHz, ppm) δ 8.17 (s, 1H), 7.76−7.71 (m, 4H), 7.46−7.37 (m, 3H), 2.21 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.8, 135.5, 133.9, 130.7, 128.8, 127.8, 127.6, 126.5, 125.1, 120.0, 116.8, 24.8; MS (ESI, positive) m/z calcd for C12H12NO+ [M + H]: 186.09, found 186.10. N-(1-Naphthyl)acetamide (3b).26 White solid (87.0 mg, 94%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.88−7.85 (m, 3H), 7.72 (d, J = 8.2 Hz, 2H), 7.55−7.46 (m, 4H), 2.33 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 169.3, 134.2, 132.5, 128.7, 127.6, 126.3, 126.13, 126.07, 125.7, 121.7, 121.1, 24.2; MS (ESI, positive) m/z calcd for C12H12NO+ [M + H]: 186.09, found 186.10. N-(Phenyl)acetamide (3c).26 White solid (63.5 mg, 94%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.50 (d, J = 7.7 Hz, 2H), 7.45 (br, 1H), 7.31 (t, J = 7.7 Hz, 2H), 7.10 (t, J = 7.4 Hz, 1H), 2.17 (s, 3H); 13 C NMR (CDCl3, 100 MHz, ppm) δ 168.6, 138.0, 129.1, 124.4, 120.0, 24.7; MS (ESI, positive) m/z calcd for C8H10NO+ [M + H]: 136.08, found 136.10. N-(4-Tolyl)acetamide (3d).8 White solid (69.4 mg, 93%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.66 (br, 1H), 7.37 (d, J = 8.3 Hz, 2H), 7.09 (d, J = 8.3 Hz, 2H), 2.30 (s, 3H), 2.13 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.4, 135.4, 134.1, 129.6, 120.2, 24.6, 21.0; MS (ESI, positive) m/z calcd for C9H12NO+ [M + H]: 150.09, found 150.10. N-(3-Tolyl)acetamide (3e).27 White solid (69.4 mg, 93%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.35 (s, 1H), 7.27 (d, J = 7.6 Hz, 1H), 7.20 (t, J = 7.6 Hz, 1H), 7.12 (br, 1H), 6.93 (d, J = 7.6 Hz, 1H), 2.34 (s, 3H), 2.17 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.7, 139.0, 138.0, 128.9, 125.2, 120.7, 117.1, 24.7, 21.6; MS (ESI, positive) m/z calcd for C9H12NO+ [M + H]: 150.09, found 150.10. N-(2-Tolyl)acetamide (3f).26 White solid (70.0 mg, 94%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.78 (d, J = 7.9 Hz, 1H), 7.23−7.18 (m, 2H), 7.09 (t, J = 7.3 Hz, 1H), 6.94 (br, 1H), 2.27 (s, 3H), 2.22 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.5, 135.8, 130.6, 129.5, 126.9, 125.5, 123.6, 24.4, 17.9; MS (ESI, positive) m/z calcd for C9H12NO+ [M + H]: 150.09, found 150.10. N-(4-Methoxyphenyl)acetamide (3g).26 White solid (79.2 mg, 96%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.50 (br, 1H), 7.38 (d, J = 9.0 Hz, 2H), 6.84 (d, J = 9.0 Hz, 2H), 3.78 (s, 3H), 2.13 (s, 3H); 13 C NMR (CDCl3, 100 MHz, ppm) δ 168.6, 156.5, 131.2, 122.1,

114.2, 55.6, 24.4; MS (ESI, positive) m/z calcd for C9H12NO2+ [M + H]: 166.09, found 166.10. N-(4-Hydroxyphenyl)acetamide (3h).28 White solid (47.6 mg, 63%). 1H NMR ((CD3)2CO, 400 MHz, ppm) δ 8.99 (br, 1H), 8.20 (s, 1H), 7.44 (d, J = 6.8, 2H), 6.76 (d, J = 6.8, 2H), 2.05 (s, 3H). 13C NMR ((CD3)2CO, 100 MHz, ppm) δ 168.5, 154.3, 132.6, 121.8, 115.9, 24.0; MS (ESI, positive) m/z calcd for C8H10NO2+ [M + H]: 152.07, found 152.10. N-(4-Fluorophenyl)acetamide (3i).26 White solid (73.5 mg, 96%). 1 H NMR (CDCl3, 400 MHz, ppm) δ 7.61 (br, 1H), 7.45 (dd, J = 4.8, 5.2 Hz, 2H), 6.99 (dd, J = 8.8 Hz, 2H), 2.15 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.7, 159.5 (J = 242.2 Hz), 134.0 (J = 1.7 Hz), 122.0 (J = 7.9 Hz), 115.7 (J = 21.9 Hz), 24.5; 19F NMR (CDCl3, 376 MHz, ppm) δ −121.2; MS (ESI, positive) m/z calcd for C8H8FNO+ [M + H]: 154.07, found 154.10. N-(4-Chlorophenyl)acetamide (3j).26 White solid (78.0 mg, 92%). 1 H NMR (CDCl3, 400 MHz, ppm) δ 7.45 (d, J = 8.7 Hz, 2H), 7.39 (br, 1H), 7.27 (d, J = 8.7 Hz, 2H), 2.17 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.4, 136.6, 129.4, 129.2, 121.2, 24.7; MS (ESI, positive) m/z calcd for C8H8ClNO+ [M + H]: 170.04, found 170.10. N-(2-Bromophenyl)acetamide (3k).29 White solid (96.3 mg, 90%).1H NMR (CDCl3, 400 MHz, ppm) δ 8.33 (d, J = 8.2 Hz, 1H), 7.62 (br, 1H), 7.53 (d, J = 8.2 Hz, 1H), 7.31 (t, J = 7.6 Hz, 1H), 6.98 (t, J = 7.6 Hz, 1H), 2.24 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.4, 135.8, 132.3, 128.5, 125.3, 122.1, 113.3, 25.0; MS (ESI, positive) m/z calcd for C8H9BrNO+ [M + H]: 213.98, found 214.00. N-(4-Nitrophenyl)acetamide (3l).30 White solid (82.8 mg, 92%).1H NMR((CD3)2CO, 400 MHz, ppm) δ 9.75 (br, 1H), 8.20 (d, J = 9.2 Hz, 2H), 7.89 (d, J = 9.2 Hz, 2H), 2.16 (s, 3H); 13C NMR ((CD3)2CO, 100 MHz, ppm) δ 169.8, 146.4, 143.6, 125.6, 119.4, 24.5; MS (ESI, negative) m/z calcd for C8H7N2O3− [M-H]: 179.05, found 179.10. N-(4-Cyanophenyl)acetamide (3m).31 White solid (72.8 mg, 91%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.67−7.60 (m, 4H), 7.45 (br, 1H), 2.23 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.7, 142.1, 133.5, 119.6, 119.0, 107.3, 24.9; MS (ESI, positive) m/z calcd for C9H9N2O+ [M + H]: 161.07, found 161.10. Methyl 4-Acetamidobenzoate (3n).26 White solid (87.9 mg, 91%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.99 (d, J = 8.6 Hz, 2H), 7.60 (d, J = 8.6 Hz, 2H), 7.60 (br, 1H), 3.90 (s, 3H), 2.21 (s, 3H); 13 C NMR (CDCl3, 100 MHz, ppm) δ 169.3, 166.9, 142.5, 130.8, 125.4, 119.0, 52.1, 24.7; MS (ESI, positive) m/z calcd for C10H12NO3+ [M + H]: 194.08, found 194.10. N-(1-Tosyl-1H-indol-3-yl)acetamide (3o).10 White solid (128.0 mg, 78%). 1H NMR (CDCl3, 400 MHz, ppm) δ 8.20 (s, 1H), 8.06 (d, J = 8.4 Hz, 1H), 7.75 (d, J = 8.2 Hz, 2H), 7.40−7.37 (m, 2H), 7.35 (t, J = 7.4 Hz, 1H), 7.23 (t, J = 7.6 Hz, 1H), 7.17 (d, J = 8.2 Hz, 2H), 2.31 (s, 3H), 2.24 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.0, 145.0, 135.1, 133.3, 129.9, 127.0, 125.5, 124.4, 123.2, 120.3, 117.0, 115, 6, 114.3, 23.9, 21.7; MS (ESI, positive) m/z calcd for C17H17N2O3S+ [M + H]: 329.10, found 329.10. N-(Benzo[b]thiophen-2-yl)acetamide (3p).32 White solid (61.2 mg, 64%).1H NMR ((CD3)2CO. 400 MHz, ppm) δ 10.4 (br, 1H), 7.78 (d, J = 8.1 1H), 7.61 (d, J = 8.1, 2H), 7.28 (t, J = 7.1, 1H), 7.21 (t, J = 7.1, 1H), 6.91 (s, 3H), 2.16 (s, 3H); 13C NMR (100 MHz, (CD3)2CO, ppm) δ 167.8, 141.4, 138.4, 136.1, 125.1, 123.4, 122.6, 122.5, 106.4, 106.3, 23.0; MS (ESI, positive) m/z calcd for C10H10NOS+ [M + H]: 192.05, found 192.10. N-Phenylbenzamide (3q).8 White solid (94.6 mg, 96%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.88 (d, J = 7.1 Hz, 2H), 7.79 (br, 1H), 7.65 (d, J = 7.9 Hz, 2H), 7.57 (t, J = 7.3 Hz, 1H), 7.50 (t, J = 7.1 Hz, 2H), 7.39 (t, J = 7.9 Hz, 2H), 7.16 (t, J = 7.4 Hz, 1H); 13C NMR (CDCl3, 100 MHz, ppm) δ 166.0, 138.1, 135.1, 132.0, 129.2, 128.9, 127.2, 124.7, 120.4; MS (ESI, positive) m/z calcd for C13H12NO+ [M + H]: 198.09, found 198.10. N-(Phenethyl)acetamide (3r).33 White solid (69.3 mg, 85%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.31 (t, J = 7.0 Hz, 2H), 7.27−7.18 (m, 3H), 5.67 (br, 1H), 3.50 (q, J = 6.7 Hz, 2H), 2.81 (t, J = 6.7 Hz, 2H), 1.93 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 170.2, 139.0, 13084

DOI: 10.1021/acs.joc.8b01810 J. Org. Chem. 2018, 83, 13080−13087

Article

The Journal of Organic Chemistry

4,5-Dihydro-1H-benzo[b]]azepin-2(3H)-one (3ac).40 White solid (57.2 mg, 71%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.71 (dd, J = 1.4, 7.4 Hz, 1H), 7.41 (dt, J = 1.4, 7.4 Hz, 1H), 7.34 (dt, J = 1.2, 7.5 Hz, 1H), 7.19 (d, J = 7.5 Hz, 1H), 6.76 (br, 1H), 3.13 (q, J = 6.8 Hz, 2H), 2.87 (t, J = 7.1 Hz, 2H), 2.03 (quin, J = 7.1 Hz, 2H); 13C NMR (CDCl3, 100 MHz, ppm) δ 175.9, 138.1, 134.4, 129.9, 127.6, 125.7, 122.0, 32.9, 30.4, 28.7; MS (ESI, positive) m/z calcd for C10H12NO+ [M + H]: 162.09, found 162.10. 7-Methylazepan-2-one (3ad).41 White solid (40.0 mg, 63%). 1H NMR (CDCl3, 400 MHz, ppm) δ 5.72 (br, 1H), 3.54−3.46 (m, 1H), 2.50−2.42 (m, 2H), 2.05−1.74 (m, 4H), 1.61−1.48 (m, 1H), 1.42− 1.32 (m, 1H), 1.21 (d, J = 6.7 Hz, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 177.9, 49.5, 37.6, 37.0, 29.9, 23.1, 22.7; MS (ESI, positive) m/ z calcd for C7H14NO+ [M + H]: 128.11, found 128.20. 3-Hydroxy-13ot-amino-13,17-seco-1,3,5(10)-estratien-17-oic 13,17-Lactam (6).22 To a 20 mL flask were added Estron (1.5 g, 4.80 mmol, 1.0 equiv), oxime 2a (1.4 g, 5.70 mmol, 1.2 equiv), and CH3CN (4.8 mL, 1.0 M) under N2 at room temperature (≈23 °C). Then H2O (90.8 μL, 5.04 mmol, 1.05 equiv) and TsOH·H2O (22.8 mg, 0.120 mmol, 2.5 mol %) were added to the stirred reaction mixture at room temperature. After 24 h, the reaction mixture was quenched by sat. NaHCO3 aq (10 mL) and extracted with ethyl acetate (30 mL × 3). The combined organic phase was washed with brine and dried over Na2SO4. The collected solution was evaporated under reduced pressure, and the remaining crude mixture was purified by silica gel column chromatography (hexane/ethyl acetate = 60/40 to 20/80, then ethyl acetate/methanol = 98/2). The obtained white solid (895 mg) was directly added to a 100 mL flask containing K2CO3 (377 mg, 2.73 mmol, 1.0 equiv) and MeOH (33 mL). The reaction mixture was stirred at room temperature for 6 h. After the starting material was consumed, the solvent was removed under reduced pressure and to the remaining solid were added H2O (4.4 mL) and CHCl3 (4.4 mL). The reaction mixture was neutralized by 0.1 N HCl and stirred at room temperature for 2 h. The suspension solution was filtered, and the remaining white powder was washed with H2O and CHCl3. The obtained white powder was dried over P2O5 under vacuum, and the desired product was isolated (750 mg, 55%). 1H NMR ((CD3)2SO, 400 MHz, ppm) δ 9.02 (s, 1H), 7.56 (s, 1H), 7.05 (ḑ J = 8.5, 1H), 6.52 (ş J = 8.4, 1H), 6.44 (br, 1H), 3.33 (s, 1H), 2.73−2.70 (m, 2H), 2.32−2.15 (m, 4H), 1.92−1.82 (m, 3H), 1.52−1.15 (m, 6H), 1.07 (s, 3H); 13C NMR ((CD3)2SO, 100 MHz, ppm) δ 169.9, 155.1, 137.0, 130.1, 126.0, 114.7, 112.8, 53.6, 50.0, 42.8, 30.7, 29.3, 26.4, 25.8, 21.9, 19.5; MS (ESI, positive) m/z calcd for C18H24NO2+ [M + H]: 286.18, found 286.10. 3-O-Sulfamyl-13ot-amino-13,17-seco-1,3,5(10) estratrien-17-oic 13,17-Lactam (7).22 To a 30 mL flask were added Estron lactam 6 (50 mg, 0.175 mmol, 1.0 equiv) and dry DMF (9.2 mL) under N2 at room temperature (≈23 °C). Then sodium hydride (60 wt % in oil) (49.2 mg, 1.23 mmol, 7.0 equiv) was added to the stirred reaction mixture at room temperature for 30 min. Then to the reaction mixture was added sulfamoyl chloride (151 mg, 1.31 mmol, 7.5 equiv), and it was stirred 18 h. The reaction was quenched by sat. NaHCO3 aq (3 mL) and extracted with ethyl acetate (30 mL × 3). The combined organic phase was washed with brine and dried over Na2SO4. The collected solution was evaporated under reduced pressure, and the remaining crude mixture was recrystallized with MeOH/acetone/ hexane. A white solid was obtained (57.4 mg, 90%). 1H NMR ((CD3)2SO, 400 MHz, ppm) δ 7.96 (s, 2H), 7.64 (br, 1H), 7.41 (ḑ J = 8.6 Hz, 1H), 7.08 (ş J = 8.5 Hz, 1H), 7.04 (s, 1H), 3.39 (s, 3H), 2.89−2.86 (m, 2H), 2.55−2.34 (m, 2H), 2.30−2.19 (m, 2H), 2.13− 1.91 (m, 3H), 1.62−1.22 (m, 6H), 1.15 (s, 3H); 13C NMR ((CD3)2SO, 100 MHz, ppm) δ 169.9, 148.1, 138.1, 138.0, 126.6, 121.6, 119.3, 53.5, 45.9, 43.0, 30.6, 29.2, 26.2, 25.4, 21.9, 19.5; MS (ESI, positive) m/z calcd for C18H25N2O4S+ [M + H]: 365.15, found 365.20.

128.9, 128.8, 126.6, 40.8, 35.7, 23.4; MS (ESI, positive) m/z calcd for C10H13NO+ [M + H]: 164.10, found 164.20. N-Nonylacetamide (3s).34 White solid (88.9 mg, 96%). 1H NMR (CDCl3, 400 MHz, ppm) δ 5.61 (br, 1H), 3.23 (q, J = 6.0 Hz, 2H), 1.97 (s, 3H), 1.51−1.47 (m, 2H), 1.30−1.26 (m, 12H), 0.88 (t, J = 6.6 Hz, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 170.1, 39.8, 32.0, 29.7, 29.6, 29.42, 29.39, 27.0, 23.5, 22.8, 14.2; MS (ESI, positive) m/z calcd for C11H24NO+ [M + H]: 186.18, found 186.20. ϵ-Caprolactam (3t).8 White solid (45.8 mg, 81%). 1H NMR (CDCl3, 400 MHz, ppm) δ 6.47 (br, 1H), 3.23−3.19 (m, 1H), 2.48− 2.45 (m, 1H), 1.79−1.62 (m, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 179.3, 43.0 36.8, 30.7, 29.9, 23.4; MS (ESI, positive) m/z calcd for C6H12NO+ [M + H]: 114.09, found 114.20. Azacyclododecan-2-one (3u).5 White solid (86.1 mg, 94%). 1H NMR (CDCl3, 400 MHz, ppm) δ 6.13 (br, 1H), 3.33−3.29 (m, 2H), 2.25−2.22 (m. 2H), 1.73−1.67 (m, 2H), 1.59−1.57 (m, 2H), 1.46− 1.34 (m, 12H); 13C NMR (CDCl3, 100 MHz, ppm) δ 173.7, 39.3, 36.4, 25.9, 25.3, 25.2, 24.7, 24.6, 24.21, 24.19, 23.3; MS (ESI, positive) m/z calcd for C11H22NO+ [M + H]: 184.17, found 184.20. Azacyclotridecan-2-one (3v).8 White solid (92.7 mg, 94%). 1H NMR (CDCl3, 400 MHz, ppm) δ 6.01 (br, 1H), 3.32−3.27 (m, 2H), 2.25−2.20 (m. 2H), 1.71−1.65 (m, 2H), 1.55−1.48 (m, 2H), 1.37− 1.30 (m, 14H); 13C NMR (CDCl3, 100 MHz, ppm) δ 173.7, 39.1, 36.9, 28.4, 26.8, 26.4, 26.2, 25.8, 25.3, 25.0, 24.7, 24.0; MS (ESI, positive) m/z calcd for C12H24NO+ [M + H]: 198.19, found 198.20. N-(6-tert-Butyl-1,1-dimethylindan-4-yl)acetamide (3w). White solid (112.8 mg, 87%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.77 (s, 1H), 7.00 (br, 1H), 6.96 (s, 1H), 2.73 (t, J = 7.1 Hz, 2H), 2.17 (s, 3H), 1.94 (t, J = 7.1 Hz, 2H), 1.31 (s, 9H), 1.25 (s, 6H); 13C NMR (CDCl3, 100 MHz, ppm) δ 168.5, 153.3, 151.0, 133.1, 130.8, 117.3, 115.5, 44.5, 41.2, 34.9, 31.6, 28.7, 27.1, 24.2; MS (ESI, positive) m/z calcd for C17H26NO+ [M + H]: 260.20, found 260.20; IR (neat) 2857, 1654, 1478, 1372, 1329, 1299, 1038, 982, 870, 777, 651, 555 cm−1; Anal. Calcd For C17H25NO: C, 9.71; H, 78.72; N, 5.40; found C, 78.74; H, 9.94; N, 5.38. Propionanilide (3x).7 White solid (68.6 mg, 92%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.52 (d, J = 8.0 Hz, 2H), 7.31 (t, J = 8.0 Hz, 2H), 7.26 (br, 1H), 7.10 (t, J = 7.4 Hz, 1H), 2.39 (q, J = 7.6 Hz, 2H), 1.25 (t, J = 7.6 Hz, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 172.1, 138.1, 129.1, 124.3, 119.9, 30.9, 9.8.MS (ESI, positive) m/z calcd for C9H12NO+ [M + H]: 150.09, found 150.10. N-Phenylisobutyramide (3y).5 White solid (mg, 95%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.87 (br, 1H), 7.54 (d, J = 8.0 Hz, 2H), 7.27 (t, J = 8.0 Hz, 2H), 7.07 (t, J = 7.3 Hz, 1H), 2.53 (sept, J = 6.9 Hz, 1H), 1.21 (d, J = 6.9 Hz, 6H); 13C NMR (CDCl3, 100 MHz, ppm) δ 175.4, 138.2, 129.1, 124.3, 119.9, 36.8, 19.7; MS (ESI, positive) m/z calcd for C10H14NO+ [M + H]: 164.11, found 164.20. N-Phenylcyclopropanecarboxamide (3z).36 White solid (74.2 mg, 91%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.63 (br, 1H), 7.50 (d, J = 7.6 Hz, 2H), 7.28 (dd, J = 7.6, 8.0 Hz, 2H), 7.08 (t, J = 7.2 Hz, 1H) 1.51−1.50 (m, 1H), 1.09−1.05 (m, 2H), 0.84−0.79 (m, 2H); 13C NMR (CDCl3, 100 MHz, ppm) δ 172.5, 138.3, 129.0, 124.1, 120.0, 15.6, 8.0; MS (ESI, positive) m/z calcd for C10H12NO+ [M + H]: 162.09, found 162.10. N-Phenylcyclohexanecarboxamide (3aa).37 White solid (78.3 mg, 77%). 1H NMR (400 MHz, CDCl3) δ 7.65 (br, 1H), 7.54 (d, J = 8.2 Hz, 2H), 7.29 (t, J = 7.6 Hz, 2H), 7.07 (t, J = 7.6 Hz, 1H), 2.28− 2.20 (m, 1H), 1.99−1.91 (m, 2H), 1.82−1.79 (m, 2H), 1.69−1.67 (m, 1H), 1.57−1.48 (m, 2H), 1.31−1.16 (m, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 174.8, 138.3, 129.0, 124.1, 120.0, 46.5, 29.7, 25.75, 25.73; MS (ESI, positive) m/z calcd for C13H18NO+ [M + H]: 204.14, found 204.10. N-(4-Methoxyphenyl)benzamide (3ab).39 White solid (64.8 mg, 57%). 1H NMR (CDCl3, 400 MHz, ppm) δ 7.85 (d, J = 8.8 Hz, 2H), 7.75 (br, 1H), 7.63 (d, J = 7.7 Hz, 2H), 7.37 (t, J = 7.7 Hz, 2H), 7.14 (t, J = 7.4 Hz, 1H), 6.98 (d, J = 8.8 Hz, 2H), 3.88 (s, 3H); 13C NMR (CDCl3, 100 MHz, ppm) δ 165.8, 156.8, 135.1, 131.8, 131.1, 128.9, 127.1, 122.3, 114.3, 55.6; MS (ESI, positive) m/z calcd for C14H14NO2+ [M + H]: 228.10, found 228.10. 13085

DOI: 10.1021/acs.joc.8b01810 J. Org. Chem. 2018, 83, 13080−13087

Article

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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.8b01810.

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Optimization, mechanistic study, and 1H and 13C NMR spectra (PDF)

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Kengo Hyodo: 0000-0002-1962-9381 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge the financial support from the Kaneka Award in Synthetic Organic Chemistry, Japan, and by the MEXT as a Supported Program for the Strategic Research foundation at Private Universities (S1311040), and partially by JSPS KAKENHI Grand (JP26107012). We are also grateful to Taiyo Nippon Sanso Co., Ltd., for providing H218O, and Prof. M. Asano (Ryukoku University) for ESI-MS measurements.

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REFERENCES

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