Cp*Co(III)-Catalyzed Dearomative [3 + 2] Spiroannulation of 2

Article pubs.acs.org/joc

Cite This: J. Org. Chem. XXXX, XXX, XXX−XXX

Cp*Co(III)-Catalyzed Dearomative [3 + 2] Spiroannulation of 2‑Alkenylphenols with Ynamides via C−H Activation Peng-Peng Lin,†,∥ Xiang-Lei Han,†,∥ Guo-Hua Ye,§ Ji-Lin Li,† Qingjiang Li,*,†,‡ and Honggen Wang*,† †

School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing 100191, China § School of Chinese Medicine, Shandong College of Traditional Chinese Medicine, Yantai 264199, China Downloaded via KAROLINSKA INST on September 7, 2019 at 03:29:51 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

‡

S Supporting Information *

ABSTRACT: An oxidative [3 + 2] C−H spiroannulation reaction of 2-alkenylphenols with ynamides has been developed toward the synthesis of spiro[4,5]decane derivatives. This dearomative reaction employs earth-abundant cobalt as the metal catalyst and occurs under rather mild reaction conditions (room temperature). The use of ynamides confers unique reactivity and exclusive regioselectivity. The products bearing an all-carbon quaternary stereogenic center were constructed in generally good yields with good functional group tolerance being observed. Experimental mechanistic studies were conducted, and a possible reaction mechanism is proposed.

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INTRODUCTION Spirocyclic skeletons are widely distributed in natural products, bioactive molecules, and ligands for metal catalyst due to their rigid three-dimensional conformational features (Figure 1).1

(Scheme 1a). Compared to naphthols, the dearomatization of phenol-derived substrates represents a more challenging task as the energy barrier of breaking the aromaticity of phenols is significantly higher.11 This is evidenced by the work of Luan where the Ru(II)-catalyzed C−H activation/spiroannulation reaction of 2-arylphenols with alkynes required a high temperature of 140 °C and an activation group para to the phenolic hydroxyl group was needed for efficiency (Scheme ́ 1b).12 Nevertheless, independent work from Lam13 and Gulias and Mascareñas14 demonstrated that the use of 2-alkenylphenols as substrates in Cp*Rh-catalyzed olefinic C−H coupling with alkynes successfully led to the dearomative spiroannulation products (Scheme 1c). In recent years, the employment of earth-abundant metals in lieu of noble metals in catalysis has received considerable attention. In this regard, the first-row cobalt-based complexes have been identified as efficient catalysts to effect a variety of C−H functionalization reactions.15 We have been interested in the unique reactivity of cobalt16 and recently reported a regioselective synthesis of 2-aminobenzoxepines by using a Cp*Co(III)-catalyzed [5 + 2] C−H annulation of 2-vinylphenols with ynamides (Scheme 1d).17 During this investigation, we observed an unexpected spirocyclic product when an additional substituent was attached to the 1-position of alkenyl moiety in 2-vinylphenol substrate (Scheme 1e). Herein, we disclose our detailed studies on a Cp*Co(III)-

Figure 1. Selected examples of spirocyclic natural products, bioactive molecules, and chiral ligands.

The synthesis of spirocycles, especially those bearing an allcarbon quaternary stereogenic center, usually suffers from low step- and atom-economy and is time-consuming.2 In this regard, the dearomative C−C bond formation reactions of planar arenes,3 for example, phenols or naphthols,4 provide valuable routes to spirocycles. Nevertheless, most of the reactions in this area necessitate the use of prefunctionalized starting materials and the use of noble metal catalysts5 and/or rely on intramolecular reactions.3d With the advances of transition-metal-catalyzed C−H activation reactions,6 the combination of C−H activation with a dearomatization reaction in a single operation offers a higher level of step- and atom-economical7 routes to spirocycles. In this regard, with the use of precious metal catalysts such as Rh,8 Ru,9 or Pd10 complex, naphthol derivatives have been known to undergo C−H activation/ dearomative cyclization with an external alkene or alkyne © XXXX American Chemical Society

Special Issue: C-H Bond Functionalization Received: June 30, 2019

A

DOI: 10.1021/acs.joc.9b01750 J. Org. Chem. XXXX, XXX, XXX−XXX

Article

The Journal of Organic Chemistry Table 1. Optimization of the Reaction Conditionsa

Scheme 1. Transition-Metal-Catalyzed C−H Functionalization/Spiroannulation of Naphthols and Phenols

entry

catalyzed dearomative oxidative [3 + 2] C−H annulation reaction of 2-alkenylphenols with ynamides, providing spiro[4,5]decanes substituted with a valuable nitrogen functionality. To the best of our knowledge, the use of cobalt in phenol dearomatization reactions is unprecedented. The reaction proceeds under surprisingly mild reaction conditions (room temperature), and a broad substrate scope was observed. The use of ynamides confers unique reactivity and exclusive regioselectivity for the reaction.

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RESULTS AND DISCUSSION The reaction of 2-(prop-1-en-2-yl)phenol 1a and N-(hex-1-yn1-yl)-N-methylmethanesulfonamide 2a was chosen as a model reaction. Under our previously reported reaction conditions (ynamide (1.0 equiv), 2-alkenylphenol (1.5 equiv), Cp*Co(CO)I2 (10 mol %), Cu(OAc)2·H2O (1.5 equiv), Ag2CO3 (0.5 equiv), and dichloroethane (DCE, 1.0 mL), air, 25 °C, 16 h (Table 1, entry 1)), the dearomative spirocycle 3aa was isolated in 60% yield, with no formation of benzoxepine or another regioisomeric product being detected. Other cobalt complexes such as Co(OAc)2, CoBr2, or Co2(CO)8 showed no reactivity for the dearomative annulation (entries 2−4). Further screening revealed that the initially used DCE was the optimal solvent (entries 5−8). The loadings of copper and silver oxidants were also examined. Either omitting Cu(OAc)2· H2O or Ag2CO3 led to a pronouncedly lower yield (entries 9 and 10), indicating a superior co-oxidant effect. Interestingly, increasing the Cu(OAc)2·H2O loading to 1.9 equiv and decreasing the Ag2CO3 loading to 0.1 equiv led to a better 69% yield (entries 11−13). Other copper or silver salts such as CuCl2·2H2O, CuBr2, AgNO3, or AgOAc exhibited less efficiency (entries 14−17). Considering the instability of phenol-derived substrate in oxidative conditions, the loading of 1a was increased to 3.0 equiv and an optimal 82% yield was obtained (entry 18). The exclusion of catalyst resulted in no formation of the desired product (entry 19), and a lower catalyst loading (5 mol %) led to significantly lower yield

[Co]

[Cu] (x equiv)

1

Cp*Co(CO)I2

2

Co(OAc)2

3

CoBr2

4

Co2(CO)8

5

Cp*Co(CO)I2

6

Cp*Co(CO)I2

7

Cp*Co(CO)I2

8

Cp*Co(CO)I2

9

Cp*Co(CO)I2

10

Cp*Co(CO)I2

11

Cp*Co(CO)I2

12

Cp*Co(CO)I2

13

Cp*Co(CO)I2

14

Cp*Co(CO)I2

15

Cp*Co(CO)I2

Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (0) Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (0.3) Cu(OAc)2·H2O (0.5) Cu(OAc)2·H2O (1.9) CuCl2·2H2O (1.5) CuBr2 (1.5)

16

Cp*Co(CO)I2

17

Cp*Co(CO)I2

18c

Cp*Co(CO)I2

19

−

20c,d

Cp*Co(CO)I2

21

[Cp*RhCl2]2

Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (1.5) Cu(OAc)2·H2O (1.9) Cu(OAc)2·H2O (1.9) Cu(OAc)2·H2O (1.9) Cu(OAc)2·H2O (1.9)

[Ag] (y equiv) Ag2CO3 (0.5) Ag2CO3 (0.5) Ag2CO3 (0.5) Ag2CO3 (0.5) Ag2CO3 (0.5) Ag2CO3 (0.5) Ag2CO3 (0.5) Ag2CO3 (0.5) Ag2CO3 (0.5) Ag2CO3 (0) Ag2CO3 (0.1) Ag2CO3 (1.5) Ag2CO3 (0.1) Ag2CO3 (0.5) Ag2CO3 (0.5) AgNO3 (1.0) AgOAc (1.0) Ag2CO3 (0.1) Ag2CO3 (0.1) Ag2CO3 (0.1) Ag2CO3 (0.1)

solvent

yieldb (%)

DCE

60

DCE

0

DCE

0

DCE

0

PhMe

54

DCM

52

TFE

0

DMF

0

DCE

trace

DCE

23

DCE

24

DCE

20

DCE

69

DCE

13

DCE

15

DCE

11

DCE

8

DCE

82

DCE

0

DCE

43

DCE

21

a

Reaction conditions: 1a (0.3 mmol, 1.5 equiv), 2a (0.2 mmol, 1.0 equiv), [Co] (10 mol %), [Cu] (x equiv), [Ag] (y equiv), solvent (1.0 mL), 25 °C, air, 16 h. bIsolated yield. c3.0 equiv of 1a was employed. d 5 mol % of Cp*Co(CO)I2 was used.

(43%, entry 20). Interestingly, the use of Cp*Rh(III) as catalyst in lieu of cobalt under otherwise identical reaction conditions gave only 21% yield, although a higher yield of 52% ́ was obtained by using the conditions of Mascareñas and Gulias 14 (not shown). Attempts to use diphenylacetylene or diethylacetylene as the coupling partner gave only a trace amount of the corresponding product (not shown), indicating the unique reactivity of ynamide in this reaction. With the optimized conditions in hand (Table 1, entry 18), the scope with regard to ynamides 2 was first examined by reacting them with 2-alkenylphenol 1a. As shown in Scheme 2, aliphatic ynamides were found to be excellent substrates for the dearomative annulation reaction, giving the corresponding B


Article

The Journal of Organic Chemistry Scheme 2. Substrate Scope of Ynamides 2a

Scheme 3. Substrate Scope of 2-Alkenylphenols 1a

a

General reaction conditions: 1 (0.6 mmol, 3.0 equiv), 2a (0.2 mmol, 1.0 equiv), [Cp*Co(CO)I2] (10 mol %), Cu(OAc)2·H2O (1.9 equiv), Ag2CO3 (0.1 equiv), DCE (1.0 mL), 25 °C, air, 16 h.

dearomative annulation reaction was unambiguously confirmed by X-ray analysis of compound 3ga.18 The practicality of this protocol was evidenced by a gramscale synthesis of 3aa (1.06 g) via the dearomative annulation of 2-alkenylphene 1a with ynamide 2a under the standard reaction conditions (Scheme 4a). The product utility was demonstrated by a chemo- and diastereoselective Diels−Alder

a

General reaction conditions: 1a (0.6 mmol, 3.0 equiv), 2 (0.2 mmol, 1.0 equiv), [Cp*Co(CO)I2] (10 mol %), Cu(OAc)2·H2O (1.9 equiv), Ag2CO3 (0.1 equiv), DCE (1.0 mL), 25 °C, air, 16 h.

Scheme 4. Gram-Scale Reaction, Product Derivatization, and Mechanistic Studies

spirocycle products in moderate to good yields. A variety of commonly encountered functional groups such as phenyl (3ab), chloro (3ac), cyano (3ad), imide (3ae), sulfonamide (3af), ester (3af, 3ag, 3ah), and alkenyl (3ah) were well tolerated. Heteroarenes including pyrrolyl (3ai) and indolyl (3aj) were also compatible with the reaction conditions. Notably, a cyclopropyl group did not interfere with the reactivity (3ak), whereas tert-butyl-substituted ynamide completely shut down the reaction, probably due to steric reasons (3al). Furthermore, the reaction of N-tosyl ynamide 2m with 1a proceeded smoothly, giving 3am in a moderate 54% yield. Unfortunately, the reaction of phenyl-substituted ynamide 2n resulted in a complicated mixture. Subsequently, the compatibility of substituted 2-alkenylphenol derivatives was studied with ynamide 2a as the coupling partner (Scheme 3). Substituents such as ethyl (3ba) and phenyl (3da) at the internal position of the alkene were well tolerated in this system, giving the corresponding spirocyclic products in moderate to good yields (58−85%). The functional group tolerance on the phenyl ring was also studied. Thus, the commonly encountered functional groups, regardless of their electronic nature, at different positions of benzene were also applicable with good efficiency, such as methyl (3ea, 3fa), methoxy (3ga, 3ha), chloro (3ja), and bromo (3ka) groups. However, the presence of a substituent on the ortho position of the alkenyl unit greatly hampered the annulation probably due to steric hindrance. Moreover, the disubstituted 2-alkenylphenol (1f) could also afford the spirocycle 3fa in spite of its reduced efficiency. The regioselectivity of this C


Article

The Journal of Organic Chemistry

being found. The use of ynamides brings unique reactivity and exclusive regioselectivity for the reaction. Mechanistic studies were conducted, and a plausible mechanism was proposed accordingly. In consideration of the ready availability of the materials and the value of the products, we anticipate that this method should be useful in organic and medicinal chemistry.

reaction of diene 3aa with diethyl but-2-ynedioate to give complex compound 4 in 72% yield (Scheme 4b). The relative stereochemistry was confirmed by NOE analysis. To gain insight regarding the reaction mechanism, several experiments were carried out. First, the introduction of radical scavenger 2,2,6,6-tetramethylpiperidineoxy (TEMPO) showed a trivial effect on the reaction efficiency, which excludes a radical mechanism involved in the reaction (Scheme 4c). Next, H/D scrambling experiments indicated that the C−H metalation step is irreversible (Scheme 4d). Finally, the kinetic isotope effect (KIE) study was conducted (Scheme 4e). A primary KIE value of 3.8 in the parallel experiments was observed, suggesting that the C−H bond cleavage is involved in the turnover-limiting step. On the basis of the above mechanistic results and previous reports,9b,13,14,17,19 a possible mechanism for this oxidative spiroannulation reaction is proposed in Scheme 5. Initially, the

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EXPERIMENTAL SECTION

General Experimental Methods. The solvents used were dried by distillation over the drying agents indicated in parentheses and were transferred under argon: 1,2-dichloroethane (CaH2), toluene (Na-benzophenone), and dichloromethane (CaH2). 2,2,2-Trifluoroethanol (TFE) and N,N-dimethylformamide (DMF) were purchased from Energy Chemical. Proton (1H) and carbon NMR (13C) were recorded on 400 and 101 MHz NMR spectrometers, respectively. The following abbreviations are used for the multiplicities: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br s, broad singlet for proton spectra. Coupling constants (J) are reported in hertz (Hz). High-resolution mass spectra (HRMS) were recorded on a BRUKER VPEXII spectrometer with EI and ESI mode unless otherwise stated, and the mass analysis mode of HRMS was TOF. Analytical thin-layer chromatography was performed on Polygram SIL G/UV254 plates. Visualization was accomplished with short-wave UV light or KMnO4 staining solutions followed by heating. Flash column chromatography was performed using silica gel (200−300 mesh) with solvents distilled prior to use. Unless otherwise noted, all reagents were commercially available and used without further purification. The starting materials, 2alkenylphenol derivatives, were prepared according to the reported method.14 The spectral data of 2-alkenylphenols 1a,14 1b,14 1c,21 1d,14 1e,14 1f,14 1g,22 1h,14 and 1j14 is consistent with the reported literature data. All ynamides were prepared from the corresponding alkenyl bromides or terminal alkynes according to the known procedures reported by Hsung23a and Stahl,23b respectively. The spectral data of ynamides 2a,24a 2b,24b 2c,17 2d,17 2e,17 2f,17 2h,17 2i,17 2j,17 2k,24c 2l,24a 2m,24d and 2n24e are consistent with the reported literature data. In addition, no attempts were made to optimize yields for substrate preparation. Analytical Characterization Data of Substrates 1i, 1k, and 2g. 3-Methoxy-2-(prop-1-en-2-yl)phenol (1i).14 Obtained as a yellow liquid (159 mg, 0.97 mmol, 39%) after column chromatography (eluent = petroleum ether/EtOAc 20:1 v/v) (PE/EA = 64/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.13 (t, J = 8.3 Hz, 1H), 6.62 (d, J = 8.3 Hz, 1H), 6.47 (d, J = 8.3 Hz, 1H), 5.72 (s, 1H), 5.55−5.44 (m, 1H), 5.13−5.04 (m, 1H), 3.82 (s, 3H), 2.10−2.05 (m, 3H). 5-Bromo-2-(prop-1-en-2-yl)phenol (1k). Obtained as a yellow liquid (344 mg, 1.62 mmol, 65%) after column chromatography (eluent = petroleum ether/EtOAc 20:1 v/v) (PE/EA = 64/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.10 (d, J = 1.8 Hz, 1H), 7.03 (dd, J = 8.2 Hz, 1.8, 1H), 6.99 (d, J = 8.2 Hz, 1H), 5.75 (s, 1H), 5.44−5.39 (m, 1H), 5.17−5.11 (m, 1H), 2.11−2.07 (m, 3H). 13 C{1H} NMR (101 MHz, CDCl3): δ 152.9, 141.4, 129.1, 128.0, 123.5, 121.6, 119.0, 116.4, 24.2. HRMS (ESI-TOF): m/z calcd for C9H10BrO [M + H]+ 212.9910, found 212.9917. 5-(N-Methylmethylsulfonamido)pent-4-yn-1-yl-(1s,3s)-adamantane-1-carboxylate (2g). Obtained as a colorless liquid (0.69 g, 1.95 mmol, 49%) after column chromatography (eluent = petroleum ether/EtOAc 10:1 v/v) (PE/EA = 8/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 4.12 (t, J = 6.5 Hz, 2H), 3.15 (s, 3H), 3.03 (s, 3H), 2.37 (t, J = 7.2 Hz, 2H), 2.06−1.96 (m, 3H), 1.91−1.78 (m, 8H), 1.76−1.60 (m, 6H). 13C{1H} NMR (101 MHz, CDCl3): δ 177.7, 75.0, 67.9, 62.7, 40.9, 39.3, 39.0, 36.6, 36.3, 28.2, 28.1, 15.3. HRMS (ESI-TOF): m/z calculated for C18H28NO4S [M + H]+ 354.1734, found 354.1739. General Procedure for the Synthesis of Products 3. 2Alkenylphenols 1 (0.6 mmol, 3.0 equiv), [Cp*Co(CO)I2] (9.7 mg, 0.02 mmol, 10 mol %), Cu(OAc)2·H2O (76 mg, 0.38 mmol, 1.9 equiv), Ag2CO3 (5.5 mg, 0.02 mmol, 0.1 equiv), DCE (1.0 mL), and

Scheme 5. Proposed Mechanism

active catalyst Cp*Co(III)Xn A is generated via the reaction of Cp*Co(CO)I2 with Cu(OAc)2·H2O or Ag2CO3. Ligand exchange of A with phenol substrate 1a gives intermediate B. Thereafter, the irreversible and turnover-limiting C−H bond cleavage occurs to deliver a six-membered cobaltacycle C. Next, the coordination and regioselective migratory insertion of ynamide 2a produces a rather strained eight-membered cobaltacycle species D, which tends to isomerize to a sixmembered complex E to release the ring strain and steric repulsion. Finally, the dearomatized product 3aa is constructed after reductive elimination, and the reduced Cp*Co(I) is oxidized by copper or silver salt to regenerate the active catalyst A. Similar to our previous observations,17 the regioselectivity may stem from the directing effect of the sulfonyl group in ynamide.20

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CONCLUSIONS In summary, we have achieved a Cp*Co(III)-catalyzed dearomative oxidative [3 + 2] C−H annulation of 2alkenylphenols with ynamides. The reaction allows the rapid and regioselective assembly of highly functionalized spirocycles bearing an all-carbon quaternary stereogenic center from readily available raw materials. The reaction proceeds under mild reaction conditions with good functional group tolerance D


Article


39.7, 38.0, 37.5, 26.9, 25.0, 13.4. HRMS (ESI-TOF): m/z calcd for C24H25N2O5S [M + H]+ 453.1479, found 453.1462. 2-(4-Methyl-1-(N-methylmethylsulfonamido)-10-oxospiro[4.5]deca-1,3,6,8-tetraen-2-yl)ethyl 4-(N,N-dipropylsulfamoyl)benzoate (3af). Following the general procedure, the product 3af was obtained as yellow liquid (71.0 mg, 0.123 mmol, 62%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/ EA = 2/1, Rf ≈ 0.20). 1H NMR (400 MHz, CDCl3): δ 8.24−8.15 (m, 2H), 7.94−7.81 (m, 2H), 7.29 (d, J = 5.1 Hz, 1H), 6.57 (d, J = 5.9 Hz, 1H), 6.36−6.22 (m, 2H), 6.06 (t, J = 7.3 Hz, 1H), 4.56 (d, J = 38.8 Hz, 2H), 3.11 (d, J = 5.9 Hz, 4H), 2.93 (s, 3H), 2.90 (s, 3H), 1.68 (d, J = 8.3 Hz, 3H), 1.60−1.49 (m, 4H), 1.26 (d, J = 8.0 Hz, 2H), 0.87 (d, J = 7.4 Hz, 4H). 13C{1H} NMR (101 MHz, CDCl3): δ 195.2, 164.2, 145.2, 145.1, 143.3, 142.4, 139.7, 138.1, 132.5, 130.1, 129.4, 127.0, 126.0, 122.5, 73.3, 62.4, 48.9, 38.6, 36.4, 26.0, 20.9, 12.3, 10.1. HRMS (ESI-TOF): m/z calcd for C28H37N2O7S2 [M + H]+ 577.2037, found 577.2056. 3-(4-Methyl-1-(N-methylmethylsulfonamido)-10-oxospiro[4.5]deca-1,3,6,8-tetraen-2-yl)propyl (1S,3S)-Adamantane-1-carboxylate (3ag). Following the general procedure, the product 3ag was obtained as yellow solid (60.2 mg, 0.124 mmol, 62%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/EA = 3/1, Rf ≈ 0.30). 1H NMR (500 MHz, CDCl3): δ 7.21 (ddd, J = 9.9, 6.0, 1.8 Hz, 1H), 6.53 (dd, J = 9.3, 5.8 Hz, 1H), 6.26 (d, J = 9.9 Hz, 1H), 6.23 (s, 1H), 6.07 (d, J = 9.2 Hz, 1H), 4.10 (q, J = 6.3 Hz, 2H), 2.92 (s, 3H), 2.87 (s, 3H), 2.43 (m, 2H), 2.01 (s, 3H), 1.94−1.82 (m, 8H), 1.76−1.68 (m, 6H). 1.66 (s, 3H). 13C{1H} NMR (126 MHz, CDCl3): δ 196.7, 177.8, 149.8, 145.7, 143.4, 141.2, 137.6, 131.7, 128.1, 123.3, 74.5, 63.6, 40.9, 39.8, 39.0, 37.6, 36.6, 28.1, 27.4, 24.1, 13.5. HRMS (ESI-TOF): m/z calcd for C27H36NO5S [M + H]+ 486.2309, found 486.2309. 3-(4-Methyl-1-(N-methylmethylsulfonamido)-10-oxospiro[4.5]deca-1,3,6,8-tetraen-2-yl)propyl Cinnamate (3ah). Following the general procedure, the product 3ah was obtained as yellow liquid (68.0 mg, 0.150 mmol, 75%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/EA = 3/1, Rf ≈ 0.30). 1H NMR (400 MHz, chloroform-d): δ 7.70 (d, J = 16.0 Hz, 1H), 7.57− 7.50 (m, 2H), 7.38 (dd, J = 5.0, 1.9 Hz, 3H), 7.21 (ddd, J = 9.8, 5.9, 1.8 Hz, 1H), 6.52 (dd, J = 9.2, 5.9 Hz, 1H), 6.44 (d, J = 16.0, 1H), 6.30−6.19 (m, 2H), 6.08 (ddd, J = 9.3, 2.0, 0.9 Hz, 1H), 4.26 (td, J = 6.4, 2.0 Hz, 2H), 2.93 (s, 3H), 2.88 (s, 3H), 2.51 (td, J = 7.3, 6.7, 1.8 Hz, 2H), 2.06−1.89 (m, 2H), 1.67 (s, 3H). 13C{ 1H} NMR (126 MHz, CDCl3): δ 196.7, 167.1, 149.7, 145.9, 144.9, 143.4, 141.2, 137.7, 134.6, 131.6, 130.4, 129.0, 128.2, 128.1, 123.3, 118.2, 74.5, 64.0, 39.7, 37.5, 27.2, 24.1, 13.5. HRMS (ESI-TOF): m/z calcd for C25H28NO5S [M + H]+ 454.1683, found 454.1679. N-(2-(3-(1H-Pyrrol-1-yl)propyl)-4-methyl-10-oxospiro[4.5]deca1,3,6,8-tetraen-1-yl)-N-methylmethanesulfonamide (3ai). Following the general procedure, the product 3ai was obtained as yellow liquid (50.6 mg, 0.136 mmol, 68%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/EA = 3/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.21 (ddd, J = 9.8, 5.9, 1.8 Hz, 1H), 6.67 (t, J = 2.1 Hz, 2H), 6.57−6.49 (m, 1H), 6.25 (dt, J = 9.8, 0.9 Hz, 1H), 6.18 (d, J = 1.6 Hz, 1H), 6.12 (t, J = 2.1 Hz, 2H), 6.06 (ddd, J = 9.2, 1.9, 0.9 Hz, 1H), 3.93 (td, J = 7.0, 2.8 Hz, 2H), 2.87 (s, 3H), 2.80 (s, 3H), 2.33 (ddd, J = 8.4, 6.5, 4.0 Hz, 2H), 2.16−1.88 (m, 2H), 1.66 (s, 3H). 13C{1H} NMR (126 MHz, CDCl3): δ 196.6, 149.1, 145.9, 143.5, 141.0, 137.6, 131.4, 128.0, 123.4, 120.6, 108.2, 74.5, 49.2, 39.6, 37.4, 29.8, 24.8, 13.5. HRMS (ESI-TOF): m/z calcd for C20H25N2O3S [M + H]+ 373.1580, found 373.1569. N-(2-(3-(1H-Indol-1-yl)propyl)-4-methyl-10-oxospiro[4.5]deca1,3,6,8-tetraen-1-yl)-N-methylmethanesulfonamide (3aj). Following the general procedure, the product 3aj was obtained as a yellow liquid (59.1 mg, 0.140 mmol, 70%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/EA = 3/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.61 (d, J = 7.8 Hz, 1H), 7.37 (d, J = 8.2 Hz, 1H), 7.20 (ddd, J = 7.1, 5.9, 2.9 Hz, 2H), 7.13 (d, J = 3.2 Hz, 1H), 7.12−7.02 (m, 1H), 6.53 (dd, J = 9.2, 5.9 Hz, 1H), 6.48 (d, J = 3.2 Hz, 1H), 6.25 (d, J = 9.8 Hz, 1H), 6.16 (d, J = 1.6 Hz, 1H), 6.08−6.02 (m, 1H), 4.19 (td, J = 7.0, 3.6 Hz, 2H), 2.82 (s, 3H), 2.68

ynamides 2 (0.2 mmol, 1 equiv) were added to a 15 mL Schlenk tube. The mixture was stirred at 25 °C for 16 h under air, and then the solvent was removed in vacuo. Purification of the residue by silica gel column chromatography afforded the desired products 3. Analytical Characterization Data of Products. N-(2-Butyl-4methyl-10-oxospiro[4.5]deca-1,3,6,8-tetraen-1-yl)-N-methylmethanesulfonamide (3aa). Following the general procedure, the product 3aa was obtained as yellow liquid (52.6 mg, 0.164 mmol, 82%) after column chromatography (eluent = petroleum ether/EtOAc 8:1 v/v) (PE/EA = 6/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.20 (ddd, J = 9.9, 6.0, 2.0 Hz, 1H), 6.51 (dd, J = 9.3, 5.9 Hz, 1H), 6.28− 6.17 (m, 2H), 6.07 (ddd, J = 9.2, 1.8, 0.8 Hz, 1H), 2.93 (s, 3H), 2.87 (s, 3H), 2.34 (td, J = 8.1, 2.7 Hz, 2H), 1.65 (s, 3H), 1.58−1.47 (m, 2H), 1.45−1.30 (m, 2H), 0.92 (t, J = 7.3 Hz, 3H). 13C{1H} NMR (101 MHz, CDCl3): δ 197.0, 151.1, 145.4, 143.4, 141.5, 136.9, 132.0, 128.1, 123.1, 74.5, 39.7, 37.7, 30.3, 27.3, 22.9, 14.1, 13.5. HRMS (ESITOF): m/ z calcd for C17H24NO3S [M + H]+ 322.1471, found 322.1459. N-Methyl-N-(4-methyl-10-oxo-2-phenethylspiro[4.5]deca1,3,6,8-tetraen-1-yl)methanesulfonamide (3ab). Following the general procedure, the product 3ab was obtained as green liquid (51.0 mg, 0.138 mmol, 69%) after column chromatography (eluent = petroleum ether/EtOAc 8:1 v/v) (PE/EA = 6/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.32−7.26 (m, 2H), 7.24−7.16 (m, 4H), 6.51 (dd, J = 9.1, 5.8 Hz, 1H), 6.27−6.22 (m, 2H), 6.03 (dd, J = 9.2, 0.9 Hz, 1H), 2.95−2.84 (m, 2H), 2.83 (s, 3H), 2.72 (s, 3H), 2.69− 2.61 (m, 2H), 1.67 (d, J = 1.6 Hz, 3H). 13C{1H} NMR (101 MHz, CDCl3): δ 196.8, 150.1, 145.7, 143.4, 141.4, 141.2, 137.5, 131.8, 128.8, 128.5, 128.1, 126.2, 123.2, 74.5, 39.6, 37.4, 34.4, 29.8, 13.5. HRMS (ESI-TOF): m/z calcd for C21H24NO3S [M + H]+ 370.1471, found 370.1456. N-(2-(3-Chloropropyl)-4-methyl-10-oxospiro[4.5]deca-1,3,6,8tetraen-1-yl)-N-methylmethanesulfonamide (3ac). Following the general procedure, the product 3ac was obtained as yellow liquid (51.3 mg, 0.150 mmol, 75%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/EA = 3/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.22 (ddd, J = 9.9, 6.0, 2.0 Hz, 1H), 6.54 (dd, J = 9.2, 5.9 Hz, 1H), 6.29−6.18 (m, 2H), 6.07 (ddd, J = 9.2, 1.9, 0.9 Hz, 1H), 3.66−3.51 (m, 2H), 2.91 (s, 3H), 2.89 (s, 3H), 2.63− 2.49 (m, 1H), 2.46 (ddd, J = 14.3, 8.4, 6.1, 1H), 2.12−1.91 (m, 2H),1.66 (s, 3H). 13C{1H} NMR (101 MHz, CDCl3): δ 196.6, 149.0, 146.1, 143.5, 141.0, 138.0, 131.5, 128.0, 123.4, 74.5, 44.6, 39.7, 37.5, 30.9, 24.8, 13.5. HRMS (ESI-TOF): m/z calcd for C16H20ClNO3S [M + H]+ 342.0925, found 342.0930. N-(2-(3-Cyanopropyl)-4-methyl-10-oxospiro[4.5]deca-1,3,6,8tetraen-1-yl)-N-methylmethanesulfonamide (3ad). Following the general procedure, the product 3ad was obtained as yellow liquid (43.2 mg, 0.130 mmol, 65%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/EA = 3/1, Rf ≈ 0.20). 1H NMR (400 MHz, CDCl3): δ 7.23 (ddd, J = 9.8, 6.0, 1.8 Hz, 1H), 6.55 (dd, J = 9.2, 5.9 Hz, 1H), 6.26 (d, J = 9.8 Hz, 1H), 6.19 (d, J = 1.6 Hz, 1H), 6.07 (dd, J = 9.2, 0.9 Hz, 1H), 2.90 (s, 3H), 2.90 (s, 3H), 2.58− 2.46 (m, 2H), 2.41 (td, J = 7.3, 1.2 Hz, 2H), 1.93 (ddt, J = 13.8, 11.1, 7.0 Hz, 2H), 1.67 (d, J = 1.5 Hz, 3H). 13C{1H} NMR (101 MHz, CDCl3): δ 196.4, 148.0, 146.5, 143.6, 140.7, 138.5, 131.0, 128.0, 123.6, 119.7, 74.5, 39.8, 37.4, 26.3, 23.9, 16.7, 13.4. HRMS (ESITOF): m/z calcd for C17H21N2O3S [M + H]+ 333.1267, found 333.1281. N-(2-(3-(1,3-Dioxoisoindolin-2-yl)propyl)-4-methyl-10-oxospiro[4.5]deca-1,3,6,8-tetraen-1-yl)-N-methylmethanesulfonamide (3ae). Following the general procedure, the product 3ae was obtained as yellow liquid (41.6 mg, 0.092 mmol, 46%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/ EA = 3/1, Rf ≈ 0.30). 1H NMR (500 MHz, CDCl3): δ 7.83 (dd, J = 5.5, 3.1 Hz, 2H), 7.70 (dd, J = 5.5, 3.1 Hz, 2H), 7.20 (ddd, J = 9.9, 6.0, 1.9 Hz, 1H), 6.51 (dd, J = 9.3, 6.0 Hz, 1H), 6.31−6.16 (m, 2H), 6.11−5.98 (m, 1H), 3.74 (td, J = 7.1, 3.7 Hz, 2H), 2.91 (s, 3H), 2.86 (s, 3H), 2.42 (dd, J = 9.3, 6.6 Hz, 2H), 2.05−1.88 (m, 2H), 1.64 (s, 3H). 13C{1H} NMR (126 MHz, CDCl3): δ 196.7, 168.5, 149.2, 145.8, 143.4, 141.2, 137.6, 134.0, 132.2, 131.4, 128.0, 123.3, 123.3, 74.5, E


Article

The Journal of Organic Chemistry (s, 3H), 2.35 (dt, J = 8.4, 6.2 Hz, 2H), 2.25−1.99 (m, 2H), 1.65 (s, 3H). 13C{ 1H} NMR (101 MHz, CDCl3): δ 196.6, 149.1, 146.0, 143.5, 140.9, 137.7, 136.0, 131.3, 128.8, 128.0, 123.4, 121.6, 121.1, 119.4, 109.6, 101.2, 74.5, 46.1, 39.4, 37.3, 28.5, 25.0, 13.5. HRMS (ESI-TOF): m/z calcd for C24H27N2O3S [M + H]+ 423.1737, found 423.1747. N-(2-Cyclopropyl-4-methyl-10-oxospiro[4.5]deca-1,3,6,8-tetraen-1-yl)-N-methylmethanesulfonamide (3ak). Following the general procedure, the product 3ak was obtained as yellow solid (26.8 mg, 0.088 mmol, 44%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/EA = 2/1, Rf ≈ 0.30). 1H NMR (400 MHz, Chloroform-d): δ 7.21−7.16 (m, 1H), 6.49 (dd, J = 9.4, 5.6 Hz, 1H), 6.23 (d, J = 9.7 Hz, 1H), 6.07 (dd, 2H), 5.79 (d, J = 1.5 Hz, 1H), 3.01 (s, 2H), 2.90 (s, 3H), 1.83−1.74 (m, 2H), 1.62 (d, J = 1.5 Hz, 3H), 0.98−0.88 (m, 2H), 0.72−0.64 (m, 2H). 13C{1H} NMR (101 MHz, CDCl3): δ 197.1, 152.2, 145.9, 143.4, 141.3, 136.1, 128.0, 127.8, 123.0, 74.8, 39.7, 37.8, 13.6, 9.4, 7.1, 7.1. HRMS (ESITOF): m/z calcd for C16H20NO3S [M + H]+ 306.1158, found 306.1158. N-(2-Butyl-4-methyl-10-oxospiro[4.5]deca-1,3,6,8-tetraen-1-yl)N,4-dimethylbenzenesulfonamide (3am). Following the general procedure, the product 3am was obtained as yellow solid (43.0 mg, 0.108 mmol, 54%) after column chromatography (eluent = petroleum ether/EtOAc 8:1 v/v) (PE/EA = 6/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.68 (d, J = 8.1 Hz, 2H), 7.30 (d, J = 8.2 Hz, 1H), 7.24 (s, 1H), 7.14−7.07 (m, 1H), 6.36 (dd, J = 9.1, 6.0 Hz, 1H), 6.21−6.13 (m, 2H), 6.04 (d, J = 9.2 Hz, 1H), 2.88 (s, 3H), 2.41 (s, 3H), 2.10−2.02 (m, 2H), 1.65 (s, 3H), 1.48−1.34 (m, 2H), 1.32− 1.19 (m, 2H), 0.86 (t, J = 7.3 Hz, 3H). 13C{1H} NMR (126 MHz, CDCl3): δ 197.0, 151.0, 146.0, 143.5, 143.3, 140.9, 137.2, 136.8, 131.8, 129.5, 127.9, 127.8, 122.8, 74.9, 38.5, 30.3, 27.4, 22.9, 21.6, 14.0, 13.6. HRMS (ESI-TOF): m/z calcd for C23H28NO3S [M + H]+ 398.1784, found 398.1769. N-(2-Butyl-4-ethyl-10-oxospiro[4.5]deca-1,3,6,8-tetraen-1-yl)-Nmethylmethanesulfonamide (3ba). Following the general procedure, the product 3ba was obtained as yellow liquid (57.0 mg, 0.170 mmol, 85%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/EA = 3/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.19 (ddd, J = 9.8, 5.9, 1.8 Hz, 1H), 6.49 (dd, J = 9.4, 5.7 Hz, 1H), 6.28−6.21 (m, 2H), 6.08 (ddd, J = 9.2, 2.0, 0.9 Hz, 1H), 2.92 (s, 3H), 2.87 (s, 3H), 2.44−2.24 (m, 2H), 1.95 (qdt, J = 7.2, 4.4, 2.4, 2H), 1.63−1.45 (m, 2H), 1.39 (dq, J = 7.3 Hz, 2H), 1.05 (t, J = 7.4 Hz, 3H), 0.93 (t, J = 7.3 Hz, 3H). 13C{1H} NMR (101 MHz, CDCl3): δ 197.0, 151.8, 151.0, 143.2, 141.7, 136.6, 129.5, 127.9, 122.8, 74.3, 39.6, 37.6, 30.2, 27.3, 22.8, 20.8, 13.9, 11.6. HRMS (ESI-TOF): m/z calcd for C18H26NO3S [M + H]+ 336.1628, found 336.1614. N-(2-Butyl-10-oxo-4-phenethylspiro[4.5]deca-1,3,6,8-tetraen-1yl)-N-methylmethanesulfonamide (3ca). Following the general procedure, the product 3ca was obtained as yellow liquid (55.1 mg, 0.134 mmol, 67%) after column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) (PE/EA = 3/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.25 (d, J = 7.4 Hz, 2H), 7.21−7.15 (m, 2H), 7.15− 7.10 (m, 2H), 6.49 (dd, J = 9.2, 5.4 Hz, 1H), 6.30 (t, J = 1.9 Hz, 1H), 6.25 (dd, J = 9.8, 0.8 Hz, 1H), 6.09 (ddd, J = 9.2, 1.8, 0.9 Hz, 1H), 2.94 (s, 3H), 2.88 (s, 3H), 2.84−2.69 (m, 2H), 2.42−2.32 (m, 2H), 2.23 (td, J = 8.2, 2.0 Hz, 2H), 1.70−1.47 (m, 4H), 1.38 (ddq, J = 13.2, 8.4, 6.7, 6.0 Hz, 2H), 0.94 (t, J = 7.3 Hz, 3H). 13C{1H} NMR (101 MHz, CDCl3): δ 196.9 151.0, 149.3, 143.4, 141.6, 141.4, 136.9, 130.9, 128.5, 128.4, 128.1, 126.2, 123.2, 74.5, 39.8, 37.7, 33.7, 30.3, 29.8, 27.4, 22.9, 14.1. HRMS (ESI-TOF): m/z calcd for C24H30NO3S [M + H]+ 412.1941, found 412.1946. N-(2-Butyl-10-oxo-4-phenylspiro[4.5]deca-1,3,6,8-tetraen-1-yl)N-methylmethanesulfonamide (3da). Following the general procedure, the product 3da was obtained as green liquid (44.0 mg, 0.115 mmol, 58%) after column chromatography (eluent = petroleum ether/EtOAc 6:1 v/v) (PE/EA = 4/1, Rf ≈ 0.20). 1H NMR (400 MHz, CDCl3): δ 7.33 (ddd, J = 9.8, 6.0, 1.8 Hz, 1H), 7.23 (d, J = 7.6 Hz, 2H), 7.19 (d, J = 7.0 Hz, 1H), 7.15 (dd, J = 7.4, 6.0 Hz, 2H), 7.04 (s, 1H), 6.58 (dd, J = 9.2, 6.0 Hz, 1H), 6.43 (d, J = 9.8 Hz, 1H), 6.23

(d, J = 8.5 Hz, 1H), 2.94 (s, 3H), 2.94 (s, 3H), 2.42 (t, J = 7.5 Hz, 2H), 1.66−1.56 (m, 2H), 1.42 (qd, J = 15.0, 7.1 Hz, 2H), 0.95 (t, J = 7.3 Hz, 3H). 13C{1H} NMR (101 MHz, CDCl3): δ 196.3, 151.8, 147.9, 143.3, 142.8, 138.7, 133.2, 131.3, 128.8, 128.4, 128.0, 125.5, 123.1, 72.6, 40.3, 37.8, 30.4, 27.6, 22.9, 14.1. HRMS (ESI-TOF): m/z calcd for C22H26NO3S [M + H]+ 384.1628, found 384.1629. N-(2-Butyl-4,8-dimethyl-10-oxospiro[4.5]deca-1,3,6,8-tetraen-1yl)-N-methylmethanesulfonamide (3ea). Following the general procedure, the product 3ea was obtained as yellow liquid (46.3 mg, 0.138 mmol, 69%) after column chromatography (eluent = petroleum ether/EtOAc 8:1 v/v) (PE/EA = 6/1, Rf ≈ 0.30). 1H NMR (500 MHz, CDCl3): δ 7.03 (dd, J = 9.8, 2.4 Hz, 1H), 6.20 (d, J = 9.9 Hz, 1H), 6.18 (d, J = 1.5 Hz, 1H), 5.70 (s, 1H), 2.91 (s, 3H), 2.83 (s, 3H), 2.36−2.29 (m, 2H), 2.02 (d, J = 1.7 Hz, 3H), 1.64 (d, J = 1.7 Hz, 3H), 1.57−1.48 (m, 2H), 1.43−1.32 (m, 2H), 0.92 (t, J = 7.3 Hz, 3H). 13C{1H} NMR (126 MHz, CDCl3): δ 197.1, 150.7, 147.5, 146.1, 137.4, 134.90, 131.4, 131.0, 127.9, 73.8, 39.4, 37.7, 30.3, 27.3, 22.8, 21.2, 14.0, 13.6. HRMS (ESI-TOF): m/z calcd for C18H26NO3S [M + H]+ 336.1628, found 336.1622. N-(2-Butyl-4,7,8-trimethyl-10-oxospiro[4.5]deca-1,3,6,8-tetraen1-yl)-N-methylmethanesulfonamide (3fa). Following the general procedure, the product 3fa was obtained as yellow liquid (29.4 mg, 0.084 mmol, 42%) after column chromatography (eluent = petroleum ether/EtOAc 8:1 v/v) (PE/EA = 6/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 6.18 (d, J = 1.6 Hz, 1H), 6.13 (s, 1H), 5.72 (s, 1H), 2.91 (s, 3H), 2.82 (s, 3H), 2.37−2.29 (m, 2H), 2.14 (d, J = 1.1 Hz, 3H), 2.02 (d, J = 1.3 Hz, 3H), 1.63 (d, J = 1.6 Hz, 4H), 1.55−1.47 (m, 2H), 1.32−1.42 (m, 2H), 0.92 (t, J = 7.3 Hz, 3H). 13C{1H} NMR (101 MHz, CDCl3): δ 196.8, 157.6, 150.7, 146.1, 137.2, 135.7, 132.8, 131.3, 126.4, 73.8, 39.4, 37.6, 30.3, 27.3, 22.9, 21.8, 19.2, 14.1, 13.7. HRMS (ESI-TOF): m/z calcd for C19H28NO3S [M + H]+ 350.1784, found 350.1769. N-(2-Butyl-8-methoxy-10-oxo-4-phenylspiro[4.5]deca-1,3,6,8tetraen-1-yl)-N-methylmethanesulfonamide (3ga). Following the general procedure, the product 3ga was obtained as yellow liquid (57.9 mg, 0.140 mmol, 70%) after column chromatography (eluent = petroleum ether/EtOAc 8:1 v/v) (PE/EA = 6/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 7.25−7.16 (m, 4H), 7.02 (s, 1H), 6.42 (dd, J = 9.8, 2.0 Hz, 1H), 6.23 (d, J = 9.8 Hz, 1H), 5.82 (d, J = 2.1 Hz, 1H), 3.88 (s, 3H), 2.99 (s, 3H), 2.93 (s, 3H), 2.42 (t, J = 7.5 Hz, 3H), 1.68−1.52 (m, 2H), 1.51−1.33 (m, 2H), 0.95 (t, J = 7.3 Hz, 3H). 13 C{1H} NMR (101 MHz, CDCl3): δ 194.8, 173.0, 151.5, 147.8, 143.3, 139.0, 133.4, 131.6, 128.8, 127.9, 125.5, 123.1, 102.3, 70.9, 56.3, 40.4, 37.8, 30.4, 27.6, 22.9, 14.1. HRMS (ESI-TOF): m/z calcd for C23H28NO4S [M + H]+ 414.1734, found 414.1736. N-(2-Butyl-7-methoxy-4-methyl-10-oxospiro[4.5]deca-1,3,6,8tetraen-1-yl)-N-methylmethanesulfonamide (3ha). Following the general procedure, the product 3ha was obtained as yellow liquid (62.6 mg, 0.178 mmol, 89%) after column chromatography (eluent = petroleum ether/EtOAc 8:1 v/v) (PE/EA = 6/1, Rf ≈ 0.30). 1H NMR (500 MHz, CDCl3): δ 6.99 (dd, J = 10.1, 3.2 Hz, 1H), 6.21 (d, J = 10.1 Hz, 1H), 6.15 (d, J = 1.5 Hz, 1H), 4.92 (d, J = 3.1 Hz, 1H), 3.65 (s, 3H), 2.90 (s, 3H), 2.86 (s, 3H), 2.36−2.26 (m, 2H), 1.68 (d, J = 1.5 Hz, 3H), 1.56−1.48 (m, 2H), 1.44−1.32 (m, 2H), 0.92 (t, J = 7.3 Hz, 3H). 13C{1H} NMR (126 MHz, CDCl3): δ 197.1, 152.0, 149.8, 147.7, 143.3, 138.6, 130.5, 129.0, 104.8, 71.8, 55.4, 39.7, 37.7, 30.2, 27.3, 22.9, 14.1, 13.7. HRMS (ESI-TOF): m/z calcd for C18H26NO4S [M + H]+ 352.1577, found 352.1571. N-(2-Butyl-8-chloro-4-methyl-10-oxospiro[4.5]deca-1,3,6,8-tetraen-1-yl)-N-methylmethanesulfonamide (3ja). Following the general procedure, the product 3ja was obtained as yellow liquid(44.2 mg, 0.124 mmol, 62%) after column chromatography (eluent = petroleum ether/EtOAc 8:1 v/v) (PE/EA = 6/1, Rf ≈ 0.30). 1H NMR (400 MHz, CDCl3): δ 6.54 (d, J = 9.7 Hz, 1H), 6.43 (s, 1H), 6.25 (s, 1H), 6.13 (d, J = 9.7 Hz, 1H), 2.93 (s, 3H), 2.89 (s, 3H), 2.33 (t, J = 6.6 Hz, 2H), 1.68 (s, 3H), 1.58−1.47 (m, 2H), 1.44−1.31 (m, 2H), 0.92 (t, J = 7.2 Hz, 3H). 13C{1H} NMR (101 MHz, CDCl3): δ 194.0, 153.2, 151.8, 145.3, 142.2, 136.9, 132.0, 126.5, 126.0, 73.3, 39.8, 37.8, 30.2, 27.4, 22.8, 14.1, 13.7. HRMS (ESI-TOF): m/z calcd for C17H23ClNO3S [M + H]+ 356.1082, found 356.1069. F



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N-(8-Bromo-2-butyl-4-methyl-10-oxospiro[4.5]deca-1,3,6,8-tetraen-1-yl)-N-methylmethanesulfonamide (3ka). Following the general procedure, the product 3ka was obtained as yellow liquid (60.8 mg, 0.152 mmol, 76%) after column chromatography (eluent = petroleum ether/EtOAc 8:1 v/v) (PE/EA = 6/1, Rf ≈ 0.30). 1H NMR (400 MHz, Chloroform-d): δ 6.67 (d, J = 8.8 Hz, 1H), 6.25 (s, 1H), 6.02 (dd, J = 10.3, 1.5 Hz, 1H), 2.93 (s, 1H), 2.89 (s, 1H), 2.33 (t, J = 6.5 Hz, 1H), 1.68 (s, 2H), 1.58−1.47 (m, 2H), 1.37 (tt, J = 13.7, 6.8 Hz, 2H), 0.92 (t, J = 7.2 Hz, 2H). 13C{1H} NMR (101 MHz, CDCl3): δ 193.4, 151. 7, 145.2, 143.7, 141.4, 136.7, 132.5, 129.8, 128.4, 73.2, 39.7, 37.7, 30.1, 27.3, 22.7, 13.9, 13.6. HRMS (ESITOF): m/z calcd for C17H23BrNO3S [M + H]+ 400.0577, found 400.0571. Synthesis of Compound 4. Diethyl (1S,2R,4R,7S,8R)-3′-Butyl-5′methyl-2′-(N-methylmethylsulfonamido)-3-oxospiro[bicyclo[2.2.2]octane-2,1′-cyclopentane]-2′,4′,5-triene-7,8-dicarboxylate (4). A solution of 3aa (32.1 mg, 0.1 mmol, 1.0 equiv) and diethyl acetylenedicarboxylate (20.4 mg, 0.12 mmol, 1.2 equiv) in o-xylene (1.0 mL) was stirred at 140 °C for 11 h. After the reaction was completed, the solvent was removed under reduced pressure and the crude product was purified by flash column chromatography (eluent = petroleum ether/EtOAc 4:1 v/v) to afford the corresponding product 4 (35.5 mg, 0.072 mmol, 72%) as a brown liquid (PE/EA = 4/1, Rf ≈ 0.20). 1H NMR (400 MHz, chloroform-d): δ 6.24 (dd, J = 10.1, 5.9 Hz, 1H), 6.06 (d, J = 6.0 Hz, 1H), 5.93 (t, J = 10.0 Hz, 1H), 4.26− 4.13 (m, 5H), 3.59 (s, 1H), 3.14 (s, 3H), 3.00 (s, 3H), 2.43−2.33 (m, 1H), 1.93−1.84 (m, 1H), 1.57−1.49 (m, 2H), 1.46 (s, 3H), 1.45− 1.32 (m, 2H), 1.31−1.24 (m, 6H), 0.93 (t, J = 7.2 Hz, 3H). 13C NMR (101 MHz, CDCl3): δ 199.1, 168.0, 164.6, 147.2, 141.8, 139.9, 139.8, 127.7, 127.4, 126.1, 117.0, 62.0, 61.7, 58.6, 51.1, 39.4, 38.0, 29.7, 29.3, 29.0, 28.0, 22.9, 18.0, 14.0, 13.8. HRMS (ESI-TOF): m/ z calcd for C25H36NO7S [M + H]+ 494.2207, found 494.2223.

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REFERENCES

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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.9b01750.

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Mechanistic studies; copies of spectra for compounds 1i, 1k, and 2g and the products 3 (PDF) Crystallographic data for 3ga (CIF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Xiang-Lei Han: 0000-0003-1951-3765 Qingjiang Li: 0000-0001-5535-6993 Honggen Wang: 0000-0002-9648-6759 Author Contributions ∥

P.-P.L. and X.-L.H. contributed equally.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We are grateful for the support of this work by National Natural Science Foundation of China (Nos. 21502242, 21472250, and 81402794) and the State Key Laboratory of Natural and Biomimetic Drugs (K20170210). We thank Miss Ling Yang in our group for her contribution to the revision of the manuscript. We thank Mr. Chuan-Jun Zhu from Beijing Eenst NMR Technology Co., Ltd., for helpful discussions regarding the NMR analysis. G


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Cp*Co(III)-Catalyzed Dearomative [3 + 2] Spiroannulation of 2

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