One-Pot Construction of Functionalized Spiro-Dihydronaphthoquinone

instance, indole alkaloids gelsemine and spindomycin A and B. 1. The versatile bioactivities exhibited by spirocyclic oxindoles include progesterone r...
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One-Pot Construction of Functionalized Spirodihydronaphthoquinone-oxindoles via Hauser−Kraus Annulation of Sulfonylphthalide with 3‑Alkylideneoxindoles Chenikkayala Sivasankara, Lakshminarayana Satham, and Irishi N. N. Namboothiri* Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India S Supporting Information *

ABSTRACT: The Hauser−Kraus annulation of sulfonylphthalide with 3-olefinic oxindole has been performed. This strategy, which involves a cascade Michael addition−Dieckmann cyclization−elimination sequence, offers rapid and convenient access to novel spiro-dihydronaphthoquinoneoxindoles in excellent yields with complete selectivity for the enolic form under mild reaction conditions.

T

Michael aldol sequence,14 Lewis acid-promoted Michael addition and cyclization,15 and Tamura cycloaddition16 are convenient approaches for the construction of the spirooxindole skeleton.17,18 Medicinal chemists have recognized that structural modification of a spiro-oxindole moiety or its incorporation into a unique scaffold with various other carbo- and heterocycles could generate novel bioactivities.19 Surprisingly, although a naphthoquinone moiety is a part of many bioactive natural products,20 it has not been integrated into a spiro-oxindole scaffold. We envision that such a hybrid system of two bioactive moieties could emerge as a potentially bioactive agent in medicinal chemistry and agrochemistry. An attractive approach for the construction of a naphthoquinone moiety is the Hauser−Kraus (HK) reaction.21 In HK annulation, a stabilized phthalide functions as a Michael donor with various acceptors such as α,β-unsaturated ketones, esters, sulfones, nitriles, nitro compounds, etc.22 The enolate then undergoes an in situ Dieckmann cyclization in the same pot, resulting in quinones in an overall annulation between phthalide as a 1,4-dipolar synthon and a Michael acceptor as the 1,2-dipolar synthon. This powerful strategy has paved the way for the synthesis of several bioactive compounds, including natural products.23 Our own recent forays into the HK reaction using sulfonylphthalides and nitroalkenes led to spiro and fused heterocycles and aminophenathrenes through one-pot multistep reactions.24 In the scenario described above, we surmised that naphthoquinone linked to oxindole in a spiro fashion can be conveniently synthesized via the HK reaction of phenylsulfonylphthalide25 as the 1,4-dipolar synthon and 3-olefinic oxindoles26 as the 1,2-dipolar synthon.27 The products would be useful building blocks in synthesis and possible bioactive agents in medicinal chemistry.

he spirocyclic oxindole skeleton is present in a number of bioactive natural products, for instance, indole alkaloids gelsemine and spindomycin A and B.1 The versatile bioactivities exhibited by spirocyclic oxindoles include progesterone receptor agonist,2 antituberculosis,3 antimalarial,4 antitumor,5 antidiabetic,6 and antiviral7 activities, to name a few. The MDM2 antagonistic properties of spirocyclic oxindoles distinguish them as selective and potent anticancer agents (Figure 1).8 There are several reports about the synthesis of spirooxindoles involving cross trienamine9 and tetraenamine catalysis,10 chiral amine-catalyzed [2+2+2] annulations,11 and enamine cascade reactions.12 Similarly, organocatalytic and other [3+2], [4+2], and [6+2] cycloadditions,13 the Michael−

Figure 1. Selected biologically active compounds containing quinone type spiro-oxindoles. © 2017 American Chemical Society

Received: October 19, 2017 Published: November 11, 2017 12939

DOI: 10.1021/acs.joc.7b02656 J. Org. Chem. 2017, 82, 12939−12944

Note

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

entry

base (equiv)

solvent

time

yield (%)b

1 2 3 4 5 6 7

Cs2CO3 (2.0) Cs2CO3 (1.0) K2CO3 (1.0) DABCO (1.0) Cs2CO3 (0.5) Cs2CO3 (1.0) Cs2CO3 (1.0)

THF THF THF THF THF toluene MeCN

15 min 30 min 24 h 72 h 7h 20 h 30 min

98 98 89 57 91 87 96

We commenced with our initial investigations by conducting the reaction between 3-olefinic oxindole 1a and phenylsulfonylphthalide 2 as the model substrates in THF at room temperature with 2 equiv of Cs2CO3 as the base (Table 1). This furnished HK adduct 3a exclusively in enolic form in 98% yield within 15 min (entry 1). Encouraged by this result, we turned our attention to developing optimal conditions for this transformation. At first, decreasing the quantity of base to 1 equiv slightly prolonged the reaction time (30 min), but the yield remained unaffected (98%, entry 2). Longer reaction times and lower yields were encountered when 1 equiv of other bases such as K2CO3 and DABCO was employed (entries 3 and 4, respectively). Decreasing the Cs2CO3 load to 0.5 equiv or changing the solvent to toluene also led to inferior results (entry 5 or 6, respectively). However, the reaction performed in the presence of 1 equiv of Cs2CO3 in MeCN provided the product in 96% yield in 30 min (entry 7), which was almost comparable with the best results obtained when 1 equiv of Cs2CO3 in THF was employed (entry 2).

a

Reactions were performed with 0.1 mmol of each reactant in 2.0 mL of solvent at rt. bAfter silica gel column chromatography.

Table 2. Scope of 3-Olefinic Oxindolea,b

a Reactions were performed with 0.3 mmol of each reactant in 6 mL of THF at rt. bYield after silica gel column chromatography. cThe yields were 55% (2 h) and 48% (30 h) when p-methyl- and p-methoxyphenylsulfonylphthalides, respectively, were employed as HK donors. dOn a 2.5 mmol scale.

12940

DOI: 10.1021/acs.joc.7b02656 J. Org. Chem. 2017, 82, 12939−12944

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The Journal of Organic Chemistry With the optimal conditions in hand (Table 1, entry 2), we turned our attention to demonstrate the generality of the HK reaction of phenylsulfonylphthalide 2 with various substituted oxindoles 1 (Table 2). We investigated the structural variation on oxindole 1, including the electronic nature and position of substituents on the aromatic ring and on the ring nitrogen. In general, various alkyl groups such as Bn, Me, allyl, and propargyl on the ring nitrogen of oxindole 1 were tolerated well to afford the corresponding products 3a−d, 3g−l, and 3n−p in excellent yields (84−99%) in short reaction times (15−80 min). On the other hand, electron-withdrawing groups such as Ac and Boc on the ring nitrogen adversely affected the yield and reaction time as reflected in the cases of 3e and 3f (50−90 min and 61−73% yield). The performance of an N-benzyl oxindole was less impressive only when a strongly electronwithdrawing group such as NO2 was present on the benzo ring para to the ring nitrogen as in 1m, furnishing the corresponding product 3m in 62% yield. However, substituents such as halo (fluoro, chloro, bromo, and iodo), alkyl, and alkoxy para to the ring nitrogen in the oxindole skeleton did not have a major influence on the reaction time or yield of products 3i−l and 3n−p (15−80 min and 84−98% yield). Arylsulfonylphthalides other than 2, namely, p-methyl- and p-methoxyphenylsulfonylphthalides, reacted sluggishly with a representative oxindole 1a and afforded the corresponding spiro-oxindole 3a in a much lower yield (Table 2, footnote c). The scalability of the HK reaction described above was demonstrated using 2.5 mmol each of oxindole 1a and phthalide 2 (Table 2, footnote d). This delivered product 3a in 94.5% yield in 45 min. The structure of the product was confirmed by detailed analysis of its IR, 1H NMR, 13C NMR, and mass spectral characteristics as well as single-crystal X-ray data (see also the Supporting Information). Interestingly, the βketoester moiety in compound 3 remained exclusively in enolic form, which was evident from the appearance of a broad signal for OH stretching in the range of 3413−3463 cm−1 in IR (KBr) and a broad singlet at ∼13.10−13.30 ppm in the 1H NMR spectrum recorded in CDCl3. Single-crystal X-ray data confirmed that the structure remained in enolic form in the solid state, as well. For instance, the enolic C−C and C−O bond lengths were 1.356 and 1.340 Å, respectively (Figure 2). A dihedral angle of 51−56° is observed between the two rings that form the spiro center. A plausible mechanism is proposed using oxindole 1a as the representative 1,2-dipolar synthon (Scheme 1). Phthalide anion I, generated by the deprotonation of phthalide 2 by Cs2CO3, becomes stabilized with the participation of the aromatic ring and carbonyl group as in II. Addition of this anion, the 1,4dipolar synthon, to the alkylideneoxindole 1a in a Michael

Scheme 1. Plausible Reaction Mechanism

fashion, with respect to the oxindole carbonyl group, generates intermediate III. The intramolecular Dieckmann type cyclization of enolate III, facilitated by the Thorpe−Ingold type effect of the sulfonyl group and the oxindole moiety, generates intermediate IV. Elimination of the sulfonyl group from hemiacetal anion IV leads to the spiro-dihydronaphthoquinone-oxindole 3a′, which remains in the more stable enolic form, 3a. In conclusion, functionalized spiro-dihydronaphthoquinone oxindole hybrids have been synthesized in good to excellent yield under mild conditions via HK annulation of a sulfonylphthalide with a variety of 3-olefinic oxindoles. Detailed spectroscopic and X-ray analysis revealed that one of the quinone carbonyls remains in 100% enolic form by virtue of its position β to an ester group.

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EXPERIMENTAL SECTION

General Information. The melting points recorded are uncorrected. NMR spectra (1H, 1H-decoupled, 13C and 1H−1H COSY, and 1H−13C HSQC) were recorded with TMS as the internal standard. The coupling constants (J values) are given in hertz. Highresolution mass spectra were recorded under ESI Q-TOF conditions. X-ray data were collected on a diffractometer equipped with graphite monochromated Mo Kα radiation. The structure was determined by direct methods shelxs97 and refined by full-matrix least-squares against F2 using shelxl97 software. Sulfonylphthalide28 and ethyl 2-(2oxindolin-3-ylidene) acetate29 were prepared by literature methods. General Procedure for the Synthesis of Spiro-dihydronaphthoquinone-oxindoles (3a−m). To a mixture of ethyl 2-(2oxindolin-3-ylidene) acetate 1 (0.3 mmol) and phenylsulfonylphthalide 2 (83 mg, 0.3 mmol) in THF (6 mL) was added Cs2CO3 (98 mg, 0.3 mmol). The resulting reaction mixture was stirred at room temperature. After completion of the reaction (monitored by TLC), the reaction mixture was concentrated in vacuo. The crude residue was subjected to silica gel column chromatography by elution with an 85/ 15 petroleum ether/ethyl acetate mixture (gradient elution). Ethyl 1-Benzyl-4′-hydroxy-1′,2-dioxo-1′H-spiro[indoline-3,2′naphthalene]-3′-carboxylate (3a). White solid: yield 129 mg, 98%;

Figure 2. X-ray structure of 3i. 12941

DOI: 10.1021/acs.joc.7b02656 J. Org. Chem. 2017, 82, 12939−12944

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The Journal of Organic Chemistry

1736 (s), 1676 (s), 1666 (s) cm−1; 1H NMR (500 MHz, CDCl3) δ 0.95 (t, J = 7.1 Hz, 3H), 1.65 (s, 9H), 3.90−3.97 (m, 1H), 4.05−4.12 (m, 1H), 6.80 (dd, J = 7.5, 1.0 Hz, 1H), 6.99 (td, J = 7.5, 1.0 Hz, 1H), 7.30 (td, J = 7.5, 1.0 Hz, 1H), 7.61 (t, J = 7.6 Hz, 1H), 7.81 (t, J = 7.6 Hz, 1H), 7.92 (d, J = 7.5 Hz, 1 Hz), 7.98 (d, J = 7.6 Hz, 1H), 8.19 (d, J = 7.6 Hz, 1H), 13.08 (br s, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 13.2, 28.2, 61.8, 63.1, 84.6, 99.6, 116.0, 122.0, 124.5, 125.6, 128.1, 129.3, 129.8, 132.3, 133.3, 135.7, 141.3, 149.2, 164.1, 170.1, 172.9, 191.1; HRMS (ES+) calcd for C25H23NO7Na (MNa+) 472.1367, found 472.1366. Ethyl 1-(4-Chlorobenzyl)-4′-hydroxy-1′,2-dioxo-1′H-spiro[indoline-3,2′-naphthalene]-3′-carboxylate (3g). White solid: yield 140 mg, 99%; mp 166−167 °C; IR (KBr) 3426 (br w), 1721 (vs), 1682 (s), 1651 (m) cm−1; 1H NMR (400 MHz, CDCl3) δ 0.83 (t, J = 7.1 Hz, 3H), 3.89−4.05 (m, 2H), 4.54 (d, J = 15.8 Hz, 1H), 5.37 (d, J = 15.8 Hz, 1H), 6.70 (d, J = 7.8 Hz, 1H), 6.83 (d, J = 7.8 Hz, 1H), 6.88 (t, J = 7.8 Hz, 1H), 7.16 (t, J = 7.8 Hz, 1H), 7.36 (d, J = 8.4 Hz, 2H), 7.50 (d, J = 8.4 Hz, 2H), 7.63 (td, J = 7.6, 0.9 Hz, 1H), 7.82 (td, J = 7.6, 0.9 Hz, 1H), 8.03 (dd, J = 7.6, 0.9 Hz, 1H), 8.22 (d, J = 7.6, 0.9 Hz, 1H), 13.20 (br s, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 13.6, 43.9, 61.4, 62.7, 99.1, 109.6, 122.3, 122.8, 125.6, 128.0, 129.0, 129.1, 129.2, 130.2, 130.8, 132.1, 133.5, 133.7, 134.2, 135.5, 144.2, 164.2, 170.4, 175.1, 191.3; HRMS (ES+) calcd for C27H20ClNO5Na (MNa+) 496.0922, found 496.0925. Ethyl 1-(4-Bromobenzyl)-4′-hydroxy-1′,2-dioxo-1′H-spiro[indoline-3,2′-naphthalene]-3′-carboxylate (3h). Light yellow solid: yield 141 mg, 91%; mp 184.5−186.5 °C; IR (KBr) 3426 (br w) 1722 (vs), 1682 (s), 1650 (s) cm−1; 1H NMR (500 MHz, CDCl3) δ 0.83 (t, J = 7.1 Hz, 3H), 3.90−3.96 (m, 1H), 3.97−4.03 (m, 1H), 4.53 (d, J = 15.8 Hz, 1H), 5.35 (d, J = 15.8 Hz, 1H), 6.69 (d, J = 7.7 Hz, 1H), 6.82 (d, J = 7.7 Hz, 1H), 6.87 (t, J = 7.7 Hz, 1H), 7.16 (t, J = 7.7 Hz, 1H), 7.44 (d, J = 8.3 Hz, 2H), 7.51 (d, J = 8.3 Hz, 2H), 7.62 (t, J = 7.6 Hz, 1H), 7.81 (t, J = 7.6 Hz, 1H), 8.02 (d, J = 7.6 Hz, 1H), 8.21 (d, J = 7.6 H, 1H), 13.20 (br s, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 13.6, 43.9, 61.4, 62.7, 99.0, 109.6, 121.7, 122.2, 122.8, 125.6, 128.0, 129.1, 129.3, 130.2, 130.7, 132.1, 132.1, 133.5, 134.7, 135.5, 144.1, 164.2, 170.4, 175.1, 191.2; HRMS (ES+) calcd for C27H20NO579BrNa (MNa+) 540.0417, found 540.0418. Ethyl 1-Benzyl-5-bromo-4′-hydroxy-1′,2-dioxo-1′H-spiro[indoline-3,2′-naphthalene]-3′-carboxylate (3i). White solid: yield 130 mg, 84%; mp 201−203 °C; IR (KBr) 3425 (br m), 1723 (vs), 1664 (br m) cm−1; 1H NMR (400 MHz, CDCl3) δ 0.83 (t, J = 7.1 Hz, 3H), 3.87−3.96 (m, 1H), 3.99−4.07 (m, 1H), 4.60 (d, J = 15.7 Hz, 1H), 5.34 (d, J = 15.7 Hz, 1H), 6.61 (d, J = 8.3 Hz, 1H), 6.93 (d, J = 1.8 Hz, 1H), 7.29 (dd, J = 8.3, 1.8 Hz, 1H), 7.31 (t, J = 7.3 Hz, 1H), 7.39 (t, J = 7.3 Hz, 2H), 7.52 (d, J = 7.3 Hz, 2H), 7.65 (td, J = 7.7, 1.0 Hz, 1H), 7.84 (td, J = 7.7, 1.0 Hz, 1H), 8.05 (dd, J = 7.7, 1.0 Hz, 1H), 8.23 (dd, J = 7.7, 1.0 Hz, 1H), 13.24 (br s, 1H); 13C{1H} NMR (100 MHz, CDCl3) δ 13.6, 44.6, 61.5, 62.5, 98.5, 111.2, 115.1, 125.3, 125.8, 127.6, 128.0, 128.2, 129.0, 130.0, 131.9, 132.3, 132.9, 133.4, 135.2, 135.7, 143.6, 164.5, 170.3, 174.5, 190.6; HRMS (ES+) calcd for C27H20BrNO5Na (MNa+) 540.0417, found 540.0417. Selected X-ray data: C27H20BrNO5, M = 518.35, triclinic, space group P1,̅ a = 8.7104(3) Å, b = 10.2793(3) Å, c = 13.7385(4) Å, α = 106.769(3)o, β = 108.072(3)°, γ = 93.497°, V = 1673.21(17) Å3, Dc = 1.559 Mg/m3, Z = 2, F(000) = 528, λ = 0.71073 Å, μ = 1.903 mm−1, total/unique reflections = 20563/3856 [R(int) = 0.0351], T = 293(2) K, θ = 2.10− 25.00°; final R [I > 2σ(I)], R1 = 0.0309, wR2 = 0.0770; R (all data), R1 = 0.0342, wR2 = 0.0787. Ethyl 1-Benzyl-5-fluoro-4′-hydroxy-1′,2-dioxo-1′H-spiro[indoline3,2′-naphthalene]-3′-carboxylate (3j). Pale yellow solid: yield 130 mg, 95%; mp 149−151 °C; IR (KBr) 3433 (br vw), 1727 (s), 1681 (m), 1655 (m) cm−1; 1H NMR (500 MHz, CDCl3) δ 0.81 (t, J = 7.1 Hz, 3H), 3.87−3.93 (m, 1H), 4.00−4.07 (m, 1H), 4.62 (d, J = 15.7 Hz, 1H), 5.34 (d, J = 15.7 Hz, 1H), 6.61 (dd, J = 7.5, 2.6 Hz, 1H), 6.66 (dd, J = 8.7, 2.6 Hz, 1H), 6.86 (td, J = 8.7, 2.6 Hz, 1H), 7.30 (t, J = 7.4 Hz, 1H), 7.39 (t, J = 7.4 Hz, 2H), 7.53 (d, J = 7.4 Hz, 2H), 7.64 (td, J = 7.6, 1.0 Hz, 1H), 7.83 (td, J = 7.6, 1.0 Hz, 1H), 8.05 (dd, J = 7.6, 1.0 Hz, 1H), 8.23 (dd, J = 7.6, 1.0 Hz, 1H), 13.26 (br s, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 13.6, 44.7, 61.5, 62.9, 98.6, 110.2 (d, J =

mp 142−144 °C; IR (KBr) 3439 (br s), 1723 (vs), 1678 (s), 1648 (s) cm−1; 1H NMR (400 MHz, CDCl3) δ 0.80 (t, J = 7.1 Hz, 3H), 3.84− 3.92 (m, 1H), 3.97−4.05 (m, 1H), 4.64 (d, J = 15.7 Hz, 1H), 5.36 (d, J = 15.7 Hz, 1H), 6.75 (dd, J = 7.6, 1.5 Hz, 1H), 6.82 (dd, J = 7.6, 1.5 Hz, 1H), 6.87 (td, J = 7.6, 1.5 Hz, 1H), 7.16 (td, J = 7.6, 1.5 Hz, 1H), 7.30 (t, J = 7.5 Hz, 1H), 7.40 (t, J = 7.5 Hz, 2H), 7.56 (d, J = 7.5 Hz, 2H), 7.62 (td, J = 7.7, 1.1 Hz, 1H), 7.82 (td, J = 7.7, 1.1 Hz, 1H), 8.04 (dd, J = 7.7, 1.1 Hz, 1H), 8.22 (dd, J = 7.7, 1.1 Hz, 1H), 13.23 (br s, 1H); 13C{1H} NMR (100 MHz, CDCl3) δ 13.6, 44.6, 61.4, 62.8, 99.2, 109.8, 122.2, 122.6, 125.6, 127.8, 127.8, 128.0, 129.0, 129.1, 130.3, 130.8, 132.1, 133.6, 135.5, 135.7, 144.5, 164.2, 170.5, 175.1, 191.3; HRMS (ES+) calcd for C27H21NO5Na (MNa+) 462.1312, found 462.1316. Ethyl 1-Allyl-4′-hydroxy-1′,2-dioxo-1′H-spiro[indoline-3,2′-naphthalene]-3′-carboxylate (3b). Yellow solid: yield 112 mg, 96%; mp 145−146 °C; IR (KBr) 3433 (br w), 1725 (s), 1676 (m), 1645 (m) cm−1; 1H NMR (400 MHz, CDCl3) δ 0.89 (t, J = 7.1 Hz, 3H), 4.09 (q, J = 7.1 Hz, 2H), 4.17 (ddt, J = 16.4, 5.0, 1.3 Hz, 1H), 4.67 (ddt, J = 16.4, 5.0, 1.3 Hz, 1H), 5.31 (dddd collapsed to dq, J = 10.3, 1.3 Hz, 1H), 5.55 (dddd collapsed to dq, J = 17.2, 1.4 Hz, 1H), 5.95 (dddd collapsed to ddt, J = 17.2, 10.3, 5.0 Hz, 1H), 6.82 (dd, J = 7.8, 1.4 Hz, 1H), 6.86−6.91 (m, 2H), 7.24 (td, J = 7.8, 1.4 Hz, 1H), 7.61 (td, J = 7.7, 1.1 Hz, 1H), 7.80 (td, J = 7.7, 1.1 Hz, 1H), 8.00 (dd, J = 7.7, 1.1 Hz, 1H), 8.20 (dd, J = 7.7, 1.1 Hz, 1H), 13.20 (br s, 1H); 13C{1H} NMR (100 MHz, CDCl3) δ 13.7, 43.0, 61.3, 62.7, 99.1, 109.6, 118.0, 122.1, 122.5, 125.5, 127.9, 129.0, 130.2, 130.8, 131.0, 132.0, 133.5, 135.4, 144.6, 164.2, 170.5, 174.6, 191.1; HRMS (ES+) calcd for C23H19NO5Na (MNa+) 412.1155, found 412.1155. Ethyl 4′-Hydroxy-1-methyl-1′,2-dioxo-1′H-spiro[indoline-3,2′naphthalene]-3′-carboxylate (3c). Yellow solid: yield 108 mg, 99%; mp 174−176 °C; IR (KBr) 3429 (br w), 1722 (s), 1679 (w), 1646 (m) cm−1; 1H NMR (400 MHz, CDCl3) δ 0.89 (t, J = 7.1 Hz, 3H), 3.13 (s, 3H), 3.90−4.06 (m, 2H), 6.78−6.87 (m, 1H), 6.90 (dd, J = 7.7, 1.2 Hz, 2H), 7.29 (dd, J = 7.7, 1.2 Hz, 1H), 7.60 (td, J = 7.8, 0.9 Hz, 1H), 7.80 (td, J = 7.8, 0.9 Hz, 1H), 7.99 (dd, J = 7.8, 0.9 Hz, 1H), 8.19 (dd, J = 7.8, 0.9 Hz, 1H), 13.18 (br s, 1H); 13C{1H} NMR (100 MHz, CDCl3) δ 13.6, 26.9, 61.4, 62.7, 99.2, 108.8, 122.1, 122.6, 125.6, 128.0, 129.2, 130.3, 130.6, 132.0, 133.5, 135.4, 145.4, 164.1, 170.5, 174.9, 191.3; HRMS (ES+) calcd for C21H17NO5Na (MNa+) 386.0999, found 386.1009. Ethyl 4′-Hydroxy-1′,2-dioxo-1-(prop-2-yn-1-yl)-1′H-spiro[indoline-3,2′-naphthalene]-3′-carboxylate (3d). Pale yellow solid: yield 114 mg, 98%; mp 203.5−205 °C; IR (KBr) 3426 (br w), 3293 (m), 1720 (s), 1680 (m), 1648 (w) cm−1; 1H NMR (500 MHz, CDCl3) δ 0.89 (t, J = 7.1 Hz, 3H), 2.29 (t, J = 2.5 Hz, 1H), 3.99−4.05 (m, 1H), 4.07−4.13 (m, 1H), 4.46 (dd, J = 17.6, 2.5 Hz, 1H), 4.79 (dd, J = 17.6, 2.5 Hz, 1H), 6.82 (d, J = 7.7 Hz, 1H), 6.92 (t, J = 7.7 Hz, 1H), 7.12 (d, J = 7.7 Hz, 1H), 7.30 (t, J = 7.7 Hz, 1H), 7.60 (t, J = 7.8 Hz, 1H), 7.80 (t, J = 7.8 Hz, 1H), 7.98 (d, J = 7.8 Hz, 1H), 8.19 (d, J = 7.8 Hz, 1H), 13.23 (br s, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 13.9, 29.9, 61.5, 62.6, 72.6, 77.1, 99.0, 110.0, 122.1, 123.0, 125.6, 128.0, 129.1, 130.2, 130.4, 132.1, 133.5, 135.5, 143.4, 164.1, 170.4, 174.0, 191.0; HRMS (ES+) calcd for C23H17NO5Na (MNa+) 410.0999, found 410.0997. Ethyl 1-Acetyl-4′-hydroxy-1′,2-dioxo-1′H-spiro[indoline-3,2′naphthalene]-3′-carboxylate (3e). White solid: yield 86 mg, 73%; mp 173−175 °C; IR (KBr) 3413 (br vw), 1762 (vs), 1716 (s), 1682 (s), 1653 (vs) cm−1; 1H NMR (400 MHz, CDCl3) δ 0.91 (t, J = 7.1 Hz, 3H), 2.72 (s, 3H), 3.92−4.02 (m, 1H), 4.03−4.12 (m, 1H), 6.82 (dd, J = 7.8, 1.2 Hz, 1H), 7.03 (td, J = 7.8, 1.2 Hz, 1H), 7.32 (td, J = 7.8, 1.2 Hz, 1H), 7.65 (td, J = 7.5, 1.0 Hz, 1H), 7.84 (td, J = 7.5, 1.0 Hz, 1H), 7.99 (dd, J = 7.5, 1.0 Hz, 1H), 8.21 (dd, J = 7.5, 1.0 Hz, 1H), 8.30 (dd, J = 7.8, 1.2 Hz, 1H), 13.09 (br s, 1H) (confirmed by 1H−1H COSY experiment); 13C{1H} NMR (125 MHz, CDCl3) δ 13.4, 26.8, 61.8, 63.3, 99.4, 117.6, 121.8, 125.3, 125.7, 128.1, 129.3, 129.5, 129.7, 132.4, 133.3, 135.8, 141.6, 164.2, 170.0, 170.8, 175.8, 191.3; HRMS (ES+) calcd for C22H17NO6Na (MNa+) 414.0948, found 414.0947. 1-tert-Butyl 3′-Ethyl 4′-hydroxy-1′,2-dioxo-1′H-spiro[indoline3,2′-naphthalene]-1,3′-dicarboxylate (3f). Pale yellow solid: yield 82 mg, 61%; mp 160−161.5 °C; IR (KBr) 3450 (br vw), 1771 (s), 12942

DOI: 10.1021/acs.joc.7b02656 J. Org. Chem. 2017, 82, 12939−12944

Note

The Journal of Organic Chemistry 7.5 Hz), 110.5 (d, J = 25.0 Hz), 115.1 (d, J = 23.8 Hz), 125.7, 127.6, 127.9, 128.1, 129.0, 130.0, 132.2, 132.4 (d, J = 7.5 Hz), 133.4, 135.4, 135.7, 140.5 (d, J = 1.3 Hz), 158.7 (d, J = 240.0 Hz), 164.4, 170.3, 174.7, 190.6; 19F NMR (470 MHz, CDCl3) δ −120.2; HRMS (ES+) calcd for C27H20FNO5Na (MNa+) 480.1218, found 480.1213. Ethyl 1-Benzyl-5-chloro-4′-hydroxy-1′,2-dioxo-1′H-spiro[indoline-3,2′-naphthalene]-3′-carboxylate (3k). Yellow solid: yield 130.5 mg, 92%; mp 198−200 °C; IR (KBr) 3437 (br w), 1730 (s), 1681 (m), 1654 (m) cm−1; 1H NMR (400 MHz, CDCl3) δ 0.83 (t, J = 7.0 Hz, 3H), 3.87−3.95 (m, 1H), 3.99−4.07 (m, 1H), 4.60 (d, J = 15.7 Hz, 1H), 5.34 (d, J = 15.7 Hz, 1H), 6.65 (d, J = 8.3 Hz, 1H), 6.81 (d, J = 2.0 Hz, 1H), 7.13 (dd, J = 8.3, 2.0 Hz, 1H), 7.30 (t, J = 7.4 Hz, 1H), 7.39 (t, J = 7.4 Hz, 2H), 7.52 (d, J = 7.4 Hz, 2H), 7.65 (td, J = 7.7, 1.0 Hz, 1H), 7.84 (td, J = 7.7, 1.0 Hz, 1H), 8.05 (dd, J = 7.7, 1.0 Hz, 1H), 8.23 (dd, J = 7.7, 1.0 Hz, 1H), 13.24 (br s, 1H); 13C{1H} NMR (100 MHz, CDCl3) δ 13.6, 44.7, 61.5, 62.6, 98.5, 110.7, 122.7, 125.8, 127.6, 127.9, 128.0, 128.2, 129.0, 129.1, 130.0, 132.3, 132.6, 133.4, 135.3, 135.7, 143.2, 164.5, 170.3, 174.6, 190.6; HRMS (ES+) calcd for C27H2035ClNO5Na (MNa+) 496.0922, found 496.0920. Ethyl 1-Benzyl-4′-hydroxy-5-iodo-1′,2-dioxo-1′H-spiro[indoline3,2′-naphthalene]-3′-carboxylate (3l). Yellow solid: yield 165 mg, 97%; mp 194−196 °C; IR (KBr) 3426 (br w), 1722 (vs), 1663 (br s) cm−1; 1H NMR (500 MHz, CDCl3) δ 0.83 (t, J = 7.1 Hz, 3H), 3.88− 3.95 (m, 1H), 3.99−4.06 (m, 1H), 4.59 (d, J = 15.7 Hz, 1H), 5.34 (d, J = 15.7 Hz, 1H), 6.51 (d, J = 8.3 Hz, 1H), 7.08 (d, J = 1.5 Hz, 1H), 7.30 (t, J = 7.3 Hz, 1H), 7.38 (t, J = 7.3 Hz, 2H), 7.46 (dd, J = 8.3, 1.5 Hz, 1H), 7.52 (d, J = 7.3 Hz, 2H), 7.65 (td, J = 7.7, 1.0 Hz, 1H), 7.84 (td, J = 7.7, 1.0 Hz, 1H), 8.05 (dd, J = 7.7, 1.0 Hz, 1H), 8.22 (dd, J = 7.7, 1.0 Hz, 1H), 13.24 (br s, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 13.6, 44.6, 61.5, 62.3, 84.9, 98.5, 111.8, 125.8, 127.6, 128.0, 128.2, 129.0, 130.0, 130.7, 132.3, 133.2, 133.4, 135.2, 135.7, 137.8, 144.3, 164.4, 170.3, 174.4, 190.6; HRMS (ES+) calcd for C27H21INO5 (MH+) 566.0459, found 566.0457. Ethyl 1-Benzyl-4′-hydroxy-5-nitro-1′,2-dioxo-1′H-spiro[indoline3,2′-naphthalene]-3′-carboxylate (3m). Colorless solid: yield 60 mg, 62%; mp 231.5−233 °C; IR (KBr) 3463 (br m), 1736 (s), 1684 (w), 1659 (w), 1521 (m), 1336 (vs) cm−1; 1H NMR (400 MHz, CDCl3) δ 0.79 (t, J = 7.1 Hz, 3H), 3.86−3.94 (m, 1H), 3.97−4.05 (m, 1H), 4.69 (d, J = 15.7 Hz, 1H), 5.38 (d, J = 15.7 Hz, 1H), 6.83 (d, J = 8.6 Hz, 1H), 7.33 (t, J = 7.3 Hz, 1H), 7.42 (t, J = 7.3 Hz, 2H), 7.52 (d, J = 7.3 Hz, 2H), 7.68 (td, J = 7.7, 1.0 Hz, 1H), 7.72 (d, J = 2.2 Hz, 1H), 7.88 (td, J = 7.7, 1.0 Hz, 1H), 8.05 (dd, J = 7.7, 1.0 Hz, 1H), 8.16 (dd, J = 8.6, 2.2 Hz, 1H), 8.27 (dd, J = 7.7, 1.0 Hz, 1H), 13.20 (br s, 1H); 13C{1H} NMR (100 MHz, CDCl3) δ 13.7, 45.0, 61.7, 62.2, 97.6, 109.2, 118.1, 126.1, 126.3, 127.7, 128.3, 128.4, 129.3, 129.8, 132.1, 132.6, 133.3, 134.6, 136.2, 143.4, 150.4, 165.0, 170.0, 175.1, 190.1; HRMS (ES+) calcd for C27H20N2O7Na (MNa+) 507.1163, found 507.1167. Ethyl 1-Benzyl-4′-hydroxy-5-methyl-1′,2-dioxo-1′H-spiro[indoline-3,2′-naphthalene]-3′-carboxylate (3n). White solid: yield 120 mg, 88%; mp 185−186.5 °C; IR (KBr) 3423 (br w), 1722 (vs), 1679 (w), 1648 (w) cm−1; 1H NMR (500 MHz, CDCl3) δ 0.83 (t, J = 7.0 Hz, 3H), 2.15 (s, 3H), 3.89−3.95 (m, 1H), 3.97−4.03 (m, 1H), 4.60 (d, J = 15.7 Hz, 1H), 5.37 (d, J = 15.7 Hz, 1H), 6.61−6.65 (unresolved m, 2H), 6.94 (d, J = 7.9 Hz, 1H), 7.29 (t, J = 7.3 Hz, 1H), 7.38 (t, J = 7.3 Hz, 2H), 7.56 (d, J = 7.3 Hz, 2H), 7.62 (t, J = 7.5 Hz, 1H), 7.81 (t, J = 7.5 Hz, 1H), 8.05 (d, J = 7.5 Hz, 1H), 8.22 (d, J = 7.5 Hz, 1H), 13.25 (br s, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 13.6, 21.0, 44.5, 61.4, 62.8, 99.3, 109.6, 122.9, 125.5, 127.6, 127.7, 128.0, 128.9, 129.3, 130.2, 130.7, 132.1, 132.2, 133.5, 135.4, 135.8, 142.0, 164.1, 170.6, 175.0, 191.4; HRMS (ES+) calcd for C28H23NO5Na (MNa+) 476.1468, found 476.1461. Ethyl 1-Benzyl-4′-hydroxy-5-methoxy-1′,2-dioxo-1′H-spiro[indoline-3,2′-naphthalene]-3′-carboxylate (3o). Yellow solid: yield 138 mg, 98%; mp 175−177 °C; IR (KBr) 3433 (br vw), 1723 (s), 1679 (m), 1654 (m) cm−1; 1H NMR (500 MHz, CDCl3) δ 0.83 (t, J = 7.1 Hz, 3H), 3.62 (s, 3H), 3.88−3.95 (m, 1H), 3.98−4.05 (m, 1H), 4.59 (d, J = 15.6 Hz, 1H), 5.35 (d, J = 15.6 Hz, 1H), 6.44 (d, J = 2.4 Hz, 1H), 6.64, 6.67 (ABq, J = 8.5 Hz; lower half further split into d, J = 2.4 Hz, 2H), 7.29 (t, J = 7.5 Hz, 1H), 7.38 (t, J = 7.5 Hz, 2H), 7.54 (d,

J = 7.5 Hz, 2H), 7.62 (td, J = 7.5, 1.0 Hz, 1H), 7.81 (td, J = 7.5, 1.0 Hz, 1H), 8.04 (dd, J = 7.5, 1.0 Hz, 1H), 8.22 (dd, J = 7.5, 1.0 Hz, 1H), 13.24 (br s, 1H); 13C{1H} NMR (125 MHz, CDCl3) δ 13.6, 44.6, 55.8, 61.4, 63.0, 99.1, 110.0, 110.1, 112.8, 125.6, 127.6, 127.8, 128.1, 128.9, 130.2, 132.1 (×2), 133.5, 135.5, 135.8, 137.9, 155.8, 164.2, 170.5, 174.8, 191.1; HRMS (ES+) calcd for C28H24NO6 (MH+) 470.1598, found 470.1598. Ethyl 1-Benzyl-4′-hydroxy-5,7-dimethyl-1′,2-dioxo-1′H-spiro[indoline-3,2′-naphthalene]-3′-carboxylate (3p). Pale yellow solid: yield 135 mg, 96%; mp 207.5−209 °C; IR (KBr) 3432 (br m), 1720 (s), 1681 (m), 1652 (m) cm−1; 1H NMR (400 MHz, CDCl3) δ 1.00 (t, J = 7.1 Hz, 3H), 2.11 (s, 3H), 2.23 (s, 3H), 4.01−4.14 (m, 2H), 4.88 (d, J = 16.7 Hz, 1H), 5.60 (d, J = 16.7 Hz, 1H), 6.48 (s, 1H), 6.74 (s, 1H), 7.28 (t, J = 7.5 Hz, 1H), 7.40 (t, J = 7.5 Hz, 2H), 7.54 (d, J = 7.5 Hz, 2H), 7.62 (td, J = 7.7, 0.9 Hz, 1H), 7.81 (td, J = 7.7, 0.9 Hz, 1H), 8.06 (dd, J = 7.7, 0.9 Hz, 1H), 8.22 (dd, J = 7.7, 0.9 Hz, 1H), 13.23 (s, 1H); 13C{1H} NMR (100 MHz, CDCl3) δ 13.7, 18.8, 20.7, 45.8, 61.4, 62.4, 99.8, 120.2, 120.8, 125.5, 126.2, 127.2, 128.1, 129.0, 130.2, 131.4, 132.0, 132.2, 133.5, 133.5, 135.4, 137.9, 139.9, 164.0, 170.6, 176.0, 191.6; HRMS (ES+) calcd for C29H26NO5 (MH+) 468.1805, found 468.1806.

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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.7b02656. Copies of NMR spectra for all the new compounds (PDF) CIF for compound 3i (CIF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Irishi N. N. Namboothiri: 0000-0002-8945-3932 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS I.N.N.N. thanks SERB, DST India for financial assistance. C.S. thanks UGC India and L.S. CSIR India for research fellowship. The authors thank Mr. T. S. Sudheesh (Department of Chemistry, Indian Institute of Technology Bombay) for help with X-ray data.

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REFERENCES

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