A Convenient Synthesis of Indolo-
and Pyrrolobenzazepines via a Threefold Norbornene-Mediated Domino
Reaction

Valentina Aureggi; Marion Davoust; Kersten M. Gericke; Mark Lautens

doi:10.1055/s-0028-1088195

LETTER

A Convenient Synthesis of Indolo- and Pyrrolobenzazepines via a Threefold Norbornene-Mediated Domino Reaction

Valentina Aureggi, Marion Davoust, Kersten M. Gericke, Mark Lautens*
Department of Chemistry, Davenport Chemical Laboratories, University of Toronto, 80 St. George Street, Toronto, ON, M5S 3H6, Canada
Fax: +1(416)9468185; e-Mail: mlautens@chem.utoronto.ca;

Abstract

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Abstract

A practical synthesis of a novel class of fused heterocycles was developed from 1-(2-iodobenzyl)-1H-pyrrole and -indoles with various bromoalkyl aryl alkynes. This palladium(0)-catalyzed norbornene-mediated domino reaction allows the efficient formation of three carbon-carbon bonds in a one-pot procedure with PdCl₂and tri-2-furylphosphine (TFP), in the presence of norbornene and Cs₂CO₃ in acetonitrile at 90 ˚C. New seven-membered-ring fused heterocycles are obtained in moderate to excellent yields.

Key words

norbornene - domino reaction - indoles - pyrroles - palladium

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References

References and Notes

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<A NAME="RS11008ST-7">7</A> Compounds 1a,b and 4 were prepared by alkylation of the corresponding pyrrole or indole with 2-bromomethyl-iodobenzene, according to a known procedure: Heaney H. Ley SV. J. Chem. Soc., Perkin Trans. 1 1973, 499

For the starting material synthesis and the optimization of the reaction conditions, see ref. 2.

General Procedure
A 10 mL sealable reaction vessel was charged with 1-(2-iodobenzyl)-1H-indole or -pyrrole (0.36 mmol, 1.2 equiv), bromoalkyl aryl alkyne (0.30 mmol, 1.0 equiv), norbornene (28 mg, 0.30 mmol, 1.0 equiv), Cs₂CO₃ (293 mg, 0.90 mmol, 3.0 equiv), PdCl₂ (5.3 mg, 0.03 mmol, 10 mol%), tri-2-furylphosphine (13.9 mg, 0.06 mmol, 20 mol%), and MeCN (3 mL). The mixture was stirred at r.t. for 10 min while being purged with argon. The tube was sealed and put into a preheated oil bath at 90 ˚C for 24 h. The reaction mixture was diluted with CH₂Cl₂, filtered onto a short plug of Celite, and washed with CH₂Cl₂. The solvent was evaporated in vacuo. The crude was purified by SiO₂ flash chromatography (pentane → pentane-EtOAc, 50:1, depending on the polarity of the product) to afford the desired compound.
Indole 3aa: ^¹H NMR (300 MHz, CDCl₃): δ = 7.68 (m, 2 H), 7.50-7.00 (m, 9 H), 6.62 (s, 1 H), 5.90 (s, 1 H), 5.05 (s, 2 H), 2.86 (t, 2 H, J = 6.5 Hz), 2.47 (m, 2 H), 1.90 (m, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 141.9, 140.6, 135.8, 134.5, 133.0, 129.6, 128.7, 128.6, 128.3, 128.0, 127.9, 127.2, 127.1, 123.7, 121.9, 121.7, 121.1, 119.8, 109.4, 91.5, 48.6, 31.5, 30.4, 24.3 ppm. HRMS (EI): m/z calcd for C₂₆H₂₁N [M⁺]: 347.1674; found: 347.1671.
Indole 3ab: ^¹H NMR (300 MHz, CDCl₃): δ = 8.35-8.29 (m, 2 H), 7.56-7.49 (m, 3 H), 7.46-7.42 (m, 1 H), 7.31-7.12 (m, 4 H), 7.06-6.99 (m, 1 H), 5.83 (s, 1 H), 5.18 (s, 2 H), 2.89 (t, 2 H, J = 6.7 Hz), 2.47-2.40 (m, 2 H), 1.93 (mc, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 149.4, 147.3, 140.3, 139.1, 135.9, 135.7, 135.3, 130.8, 130.3, 128.8, 128.6, 128.1, 125.8, 124.2, 122.2, 121.0, 120.0, 108.9, 102.7, 47.9, 31.7, 30.2, 24.2 ppm. HRMS (EI): m/z calcd for C₂₆H₂₀N₂O₂ [M⁺]: 392.1520; found: 392.1525.
Indole 3ac: ^¹H NMR (300 MHz, CDCl₃): δ = 7.50 (m, 2 H), 7.43 (m, 2 H), 7.38 (m, 1 H), 7.33 (m, 1 H), 7.28 (m, 1 H), 7.24 (m, 1 H), 7.19 (m, 1 H), 7.12 (m, 1 H), 7.0 (dt, 1H, J = 7.1, 7.9 Hz), 5.94 (s, 1 H), 5.23 (d, 1 H, J = 13.9 Hz), 5.17 (d, 1 H, J = 13.9 Hz), 2.80 (m, 2 H), 2.48 (m, 1 H), 2.35 (m, 1 H), 1.86 (m, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 140.6, 140.4, 138.8, 135.9, 135.6, 135.4, 135.0, 133.4, 130.6, 129.9, 129.3, 128.6, 128.1 (2), 128.0, 127.0, 125.6, 121.4, 120.7, 119.4, 108.6, 101.2, 47.7, 31.0, 30.3, 23.5 ppm. HRMS (EI): m/z calcd for C₂₆H₂₀NCl [M⁺]: 381.1284; found: 381.1293.
Indole 3ad: ^¹H NMR (300 MHz, CDCl₃): δ = 7.50 (br d, 1 H, J = 6.1 Hz), 7.44-7.32 (m, 2 H), 7.30-6.94 (m, 8 H), 5.95 (s, 1 H), 5.17 (s, 2 H), 3.73 (s, 3 H), 2.85-2.78 (m, 2 H), 2.57-2.45 (m, 1 H), 2.41-2.30 (m, 1 H), 1.86 (m_c, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 156.8, 140.4, 140.3, 136.3, 136.1, 135.6, 134.9, 131.5, 130.7, 128.8, 128.6, 128.4, 128.3, 127.9, 125.6, 121.3, 120.9, 120.8, 119.4, 111.5, 108.7, 101.0, 55.9, 47.9, 31.4, 30.6, 23.9. HRMS (EI): m/z calcd for C₂₇H₂₃NO [M⁺]: 377.1780; found: 377.1780.
Indole 3bd: ^¹H NMR (300 MHz, CDCl₃): δ = 8.18 (br s, 1 H), 7.87 (d, 1 H, J = 8.6 Hz), 7.45 (d, 1 H, J = 8.8 Hz), 7.37 (br t, 1 H, J = 7.8 Hz), 7.32-7.18 (m, 4 H), 7.15-6.96 (m, 3 H), 6.04 (s, 1 H), 5.18 (s, 2 H), 3.88 (s, 3 H), 3.74 (s, 3 H), 2.86-2.78 (m, 2 H), 2.60-2.45 (m, 1 H), 2.42-2.28 (m, 1 H), 1.94-1.80 (m_c, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 168.5, 156.7, 141.7, 140.5, 137.8, 136.1, 135.9, 135.6, 131.1, 130.6, 129.0, 128.6, 128.2, 127.8, 125.7, 123.8, 122.7, 121.4, 121.0, 111.5, 108.3, 102.3, 55.9, 51.9, 48.1, 31.4, 30.6, 23.8. HRMS (EI): m/z calcd for C₂₉H₂₆NO₃ [M + H⁺]: 436.1926; found: 436.1907.
Indole 3ae: ^¹H NMR (300 MHz, CDCl₃): δ = 8.06 (m, 2 H), 7.52 (m, 3 H), 7.42 (d, 1 H, J = 7.9 Hz), 7.28-7.15 (m, 4 H), 7.00 (m, 1 H), 5.85 (s, 1 H), 5.17 (s, 2 H), 4.38 (q, 2 H, J = 7.1 Hz), 2.86 (t, 2 H, J = 6.5 Hz), 2.45 (t, 2 H, J = 6.3 Hz), 1.90 (m, 2 H), 1.39 (t, 3 H, J = 7.1 Hz). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 166.8, 142.8, 140.2 (2), 136.3, 135.8, 135.7, 134.9, 134.1, 131.5, 131.2, 130.8, 128.8, 128.4, 128.5, 128.3, 128.2, 125.7, 121.9, 120.9, 119.8, 108.8,102.6, 61.3, 47.9, 31.7, 30.3, 24.3, 14.6. HRMS (EI): m/z calcd for C₂₉H₂₅NO₂ [M⁺]: 419.1885; found: 419.1882.
Indole 3af: ^¹H NMR (300 MHz, CDCl₃): δ = 7.95 (d, 1 H, J = 8.3 Hz), 7.90 (m, 2 H), 7.60-7.30 (m, 8 H), 7.16 (m, 2 H), 6.96 (m, 1 H), 5.84 (s, 1 H), 5.30 (s, 2 H), 2.82 (t, 2 H, J = 6.4 Hz), 2.47 (m, 1 H), 2.24 (m, 1 H), 1.78 (m, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 140.6, 140.0, 135.9, 135.7 (2), 134.2, 131.8, 130.4, 128.6 (2), 128.5, 128.3 (2), 128.2, 127.7, 126.8, 126.5, 126.1, 126.0(2), 125.8, 121.7, 120.9, 119.6, 108.7, 102.0, 48.2, 31.5, 30.6, 24.0. HRMS (EI):
m/z calcd for C₃₀H₂₃N [M⁺]: 397.1813; found: 397.1843.
Indole 3ag: ^¹H NMR (300 MHz, CDCl₃): δ = 8.10-8.05 (m, 1 H), 7.82-7.77 (m, 2 H), 7.60 (s, 1 H), 7.51 (br d, 1 H, J = 8.2 Hz), 7.38-7.11 (m, 10 H), 6.99 (m_c, 1 H), 5.79 (s,
1 H), 5.20 (s, 2 H), 2.84 (t, 2 H, J = 6.5 Hz), 2.52-2.42
(m, 2 H), 2.37 (s, 3 H), 1.96 (m_c, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 145.2, 140.4, 137.8, 136.1, 135.9, 135.7, 135.5, 135.4, 131.2, 130.1, 128.6, 128.4, 128.2, 127.0, 125.7, 125.2, 124.6, 123.9, 121.9, 121.8, 120.8, 120.6, 119.7, 114.3, 108.8, 101.6, 139.5, 124.4, 48.0, 31.6, 30.4, 24.3, 21.9. HRMS (EI): m/z calcd for C₃₅H₂₉N₂O₂S [M + H⁺]: 541.1921; found: 541.1944.
Indole 3bg: ^¹H NMR (300 MHz, CDCl₃): δ = 8.12-8.07 (m, 2 H), 7.89 (dd, 1 H, J = 8.7, 1.6 Hz), 7.81-7.76 (m, 2 H), 7.60 (s, 1 H), 7.50 (br d, 1 H, J = 8.9 Hz), 7.39-7.14 (m, 8 H), 5.80 (s, 1 H), 5.21 (s, 2 H), 3.88 (s, 3 H), 2.86 (t, 2 H, J = 6.5 Hz), 2.55-2.45 (m, 2 H), 2.41 (s, 3 H), 1.96 (m, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 168.3, 145.4, 140.6, 138.8, 137.9, 135.9, 135.6, 135.4, 135.4, 131.0, 130.2, 128.9, 128.7, 127.6, 127.0, 125.8, 125.3, 124.7, 124.2, 124.0, 123.8, 123.1, 121.7, 121.5, 120.4, 114.4, 108.5, 102.9, 52.0, 48.3, 31.7, 30.4, 24.2, 21.8. HRMS (EI): m/z calcd for C₃₇H₃₁ON₂O₄S [M + H⁺]: 599.1968; found: 599.1999.
Pyrrole 5a: ^¹H NMR (300 MHz, CDCl₃): δ = 7.40 (m, 1 H), 7.30 (m, 4 H), 7.18 (d, 1 H, J = 7.3 Hz), 7.12 (m, 2 H), 6.70 (m, 1 H, J = 2.5 Hz), 6.04 (dd, 1 H, J = 3.7, 2.6 Hz), 5.58 (dd, 1 H, J = 3.7, 1.8 Hz), 4.93 (s, 2 H), 2.84 (t, 2 H, J = 6.5 Hz), 2.40 (br s, 2 H), 1.90-1.82 (m, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 142.9, 139.9, 136.7, 135.4, 132.7, 130.3, 129.5, 128.5 (2), 128.2, 127.6, 126.9, 125.5, 120.5, 110.1, 108.4, 52.8, 31.2, 30.6, 24.5. HRMS (EI): m/z calcd for C₂₂H₁₉N [M⁺]: 297.1517; found: 297.1522.
Pyrrole 5b: ^¹H NMR (400 MHz, CDCl₃): δ = 8.29 (d, 2 H, J = 8.8 Hz), 7.48 (d, 2 H, J = 8.8 Hz), 7.24-7.22 (m, 1 H), 7.16-7.13 (m, 2 H), 6.74 (dd, 1 H, J = 2.5, 1.8 Hz), 6.07 (dd, 1 H, J = 3.7, 2.6 Hz), 5.52 (dd, 1 H, J = 3.7, 1.7 Hz), 4.96 (s, 2 H), 2.87 (t, 2 H, J = 6.5 Hz), 2.37 (t, 2 H, J = 6.5 Hz), 1.88 (quint, 2 H, J = 6.5 Hz). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 149.7, 147.0, 139.9, 135.9, 135.3, 132.8, 131.1, 130.6, 130.4, 128.6, 128.1, 125.6, 123.9, 121.1, 110.2, 108.6, 52.7, 31.2, 30.3, 24.3. HRMS (EI): m/z calcd for C₂₂H₁₈N₂O₂ [M⁺]: 342.1368; found: 342.1383.
Pyrrole 5c: ^¹H NMR (300 MHz, CDCl₃): δ = 7.46 (m, 1 H), 7.30 (m, 4 H), 7.14-7.02 (m, 2 H), 6.69 (dd, 1 H, J = 2.5, 1.8 Hz), 6.05 (dd, 1 H, J = 3.6, 2.6 Hz), 5.62 (dd, 1 H, J = 3.6, 1.6 Hz), 4.89 (s, 2 H), 2.83-2.70 (m, 2 H), 2.39 (m, 1 H), 2.28 (m, 1 H), 1.81 (m, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 141.0, 140.5, 135.7, 135.5, 132.4, 130.9, 130.5, 129.7, 129.5, 128.3, 127.9 (2), 127.6, 126.9, 125.5, 120.3, 108.9, 108.3, 52.4, 30.6, 30.5, 23.6. HRMS (EI): m/z calcd for C₂₂H₁₈NCl [M⁺]: 331.1128; found: 331.1136.
Pyrrole 5d: ^¹H NMR (300 MHz, CDCl₃): δ = 7.34-7.29 (m, 1 H), 7.20-7.08 (m, 4 H), 7.02-6.95 (m, 2 H), 6.66 (dd, 1 H, J = 2.4, 1.8 Hz), 6.03 (dd, 1 H, J = 3.6, 2.6 Hz), 5.64 (dd, 1 H, J = 3.6, 1.7 Hz), 4.97 (d, 1 H, J = 13.5 Hz), 4.90 (d, 1 H, J = 13.4 Hz) 3.75 (s, 3 H), 2.80-2.76 (m, 2 H), 2.42-2.28 (m, 2 H), 1.85-1.79 (m, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 157.4, 138.9, 134.5, 130.6, 129.6, 129.5, 127.2, 126.9, 126.2, 124.3, 123.8, 119.6, 118.8, 117.6, 110.1 (2), 107.6, 107.0, 54.6, 51.4, 29.8, 29.6, 22.7. HRMS (EI): m/z calcd for C₂₃H₂₁NO [M⁺]: 327.1627; found: 327.1623.
Pyrrole 5e: ^¹H NMR (300 MHz, CDCl₃): δ = 8.04-8.00 (m, 1 H), 7.99-7.97 (m, 1 H), 7.50-7.48 (m, 2 H), 7.22-7.19 (m, 1 H), 7.15-7.10 (m, 2 H), 6.72 (dd, 1 H, J = 1.8, 2.5 Hz), 6.04 (dd, 1 H, J = 2.5, 3.7 Hz), 5.54 (dd, 1 H, J = 1.8, 3.7 Hz), 4.94 (s, 2 H), 4.38 (q, 2 H, J = 7.1 Hz), 2.84 (t, 2 H, J = 6.4 Hz), 2.37 (m, 2 H), 1.86 (quint, 2 H, J = 6.4 Hz), 1.39 (t, 3 H, J = 7.1 Hz). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 166.8, 143.0, 139.9, 136.3, 135.4, 133.9, 133.8, 131.6, 130.9, 130.7 (2), 128.6, 128.4, 128.1, 127.7, 125.5, 120.7, 110.1, 108.4, 61.2, 52.7, 31.2, 30.4, 24.3, 14.5. HRMS (EI): m/z calcd for C₂₅H₂₃NO₂ [M⁺]: 369.1729; found: 369.1721.
Pyrrole 5f: ^¹H NMR (300 MHz, CDCl₃): δ = 7.92 (d, 1 H, 8.3 Hz), 7.86 (m, 2 H), 7.53 (m, 1 H), 7.46 (m, 1 H), 7.40 (m, 2 H), 7.23 (d, 1 H, J = 9.2 Hz), 7.20 (m, 1 H), 7.14 (m, 1 H), 6.71 (dd, 1 H, J = 2.5, 1.8 Hz), 5.97 (dd, 1 H, J = 3.7, 2.6 Hz), 5.51 (br s, 1 H), 5.06 (s, 2 H), 2.78 (t, 2 H, J = 6.2 Hz), 2.38 (m, 1 H), 2.17 (m, 1 H), 1.73 (m, 2 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 140.3 (2), 136.4, 135.5, 134.1, 133.8, 131.7, 128.5 (2), 128.3, 127.7, 127.3, 126.3, 126.1, 126.0(2), 125.7, 120.7, 120.6, 109.7, 108.5, 53.0, 31.0, 30.8, 24.0. HRMS (EI): m/z calcd for C₂₆H₂₁N [M⁺]: 347.1674; found: 347.1667.
Pyrrole 5g: ^¹H NMR (400 MHz, CDCl₃): δ = 7.23-7.16 (m, 5 H), 7.14-7.10 (m, 2 H), 6.70-6.69 (m, 1 H), 6.05 (dd, 1 H, J = 3.7, 2.6 Hz), 5.60 (dd, 1 H, J = 3.7, 1.7 Hz), 4.93 (s, 2 H), 2.85 (t, 2 H, J = 6.5 Hz), 2.43-2.39 (m, 2 H), 2.41 (s, 3 H), 1.87 (quint, 2 H, J = 6.4 Hz). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 139.9, 139.8, 136.7, 136.3, 135.3, 132.6, 130.2, 129.3, 129.1, 128.9, 128.3, 127.4, 125.3, 120.4, 109.9, 108.3, 52.7, 31.1, 30.5, 24.5, 21.4. HRMS (EI): m/z calcd for C₂₃H₂₁N [M⁺]: 311.1674; found: 311.1668.
Pyrrole 5h: ^¹H NMR (300 MHz, CDCl₃): δ = 7.23-7.18 (m, 1 H), 7.13-7.08 (m, 2 H), 6.72 (dd, 1 H, J = 2.3, 2.0 Hz), 6.51 (s, 2 H), 6.08 (dd, 1 H, J = 3.7, 2.6 Hz), 5.73 (dd, 1 H, J = 3.7, 1.7 Hz), 4.93 (s, 2 H), 3.91 (s, 3 H), 3.86 (s, 6 H), 2.86 (t, 2 H, J = 6.5 Hz), 2.48-2.40 (m, 2 H), 1.89 (quint, 2 H, J = 6.4 Hz). ^¹³C NMR (100 MHz, CDCl₃): δ = 153.3, 139.7, 138.3, 136.8, 136.5, 135.3, 133.8, 132.4, 130.4, 128.4, 127.6, 125.4, 120.6, 109.8, 108.3, 106.4, 61.1, 56.3, 52.7, 31.1, 30.4, 24.5. ESI-HRMS: m/z calcd for C₂₅H₂₆NO₃ [M + H⁺]: 388.1894; found: 388.1907.
Compound 7b: ^¹H NMR (400 MHz, CDCl₃): δ = 8.12-8.09 (m, 2 H), 7.77-7.74 (m, 1 H), 7.23-7.19 (m, 1 H), 7.13-7.08 (m, 2 H), 6.49 (t, 2 H, J = 2.1 Hz), 6.08 (t, 2 H, J = 2.1 Hz), 5.32 (d, 1 H, J = 14.6 Hz), 5.01 (d, 1 H, J = 14.6 Hz), 3.31-3.23 (m, 1 H), 3.09 (d, 1 H, J = 7.7 Hz), 2.92 (d, 1 H, J = 7.8 Hz), 2.64 (dt, 1 H, J = 13.8, 3.1 Hz), 2.57-2.51 (m, 1 H), 2.35 (d, 1 H, J = 4.2 Hz), 2.30 (dt, 1 H, J = 4.3, 13.5 Hz), 2.14-2.07 (m, 1 H), 1.56-1.47 (m, 1 H), 1.46-1.36 (m, 2 H), 1.35-1.19 (m, 2 H), 0.96-0.81 (m, 3 H). ^¹³C NMR (75.5 MHz, CDCl₃): δ = 151.7, 149.6, 147.1, 142.8, 142.2, 138.2, 135.4, 134.0, 127.9, 127.5, 126.0, 125.1, 122.3, 121.0, 120.5, 108.3, 53.6, 52.0, 51.4, 43.7, 41.1, 32.6, 30.1, 29.6, 29.1, 28.4, 22.8. HRMS (EI): m/z calcd for C₂₉H₂₈N₂O₂ [M⁺]: 436.2151; found: 436.2166.
Compound 7e: ^¹H NMR (400 MHz, CDCl₃): δ = 8.34 (br s, 1 H), 7.92 (dd, 1 H, J = 7.9, 1.2 Hz), 7.32 (d, 1 H, J = 7.9 Hz), 7.18-7.14 (m, 1 H), 7.10-7.03 (m, 2 H), 6.54 (t, 2 H, J = 2.1 Hz), 6.09 (t, 2 H, J = 2.1 Hz), 5.33 (d, 1 H, J = 14.6 Hz), 5.02 (d, 1 H, J = 14.6 Hz), 4.45-4.37 (m, 2 H), 3.41-3.33 (m, 1 H), 3.04 (d, 1 H, J = 7.6 Hz), 2.85 (d, 1 H, J = 7.5 Hz), 2.66-2.55 (m, 2 H), 2.34-2.26 (m, 2 H), 2.15-2.07 (m, 1 H), 1.56-1.45 (m, 1 H), 1.44-1.34 (m, 2 H), 1.42 (t, 3 H, J = 7.1 Hz), 1.33-1.17 (m, 2 H), 0.96-0.94 (m, 1 H), 0.91-0.84 (m, 1 H), 0.79-0.76 (m, 1 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 171.3, 167.1, 155.6, 143.5, 142.8, 138.7, 134.0, 131.0, 129.2, 129.0, 127.3, 127.0, 126.3, 125.7, 125.2, 121.0, 108.2, 61.1, 53.4, 52.5, 51.2, 43.7, 41.0, 32.7, 30.2, 29.3, 29.2, 28.5, 23.2, 14.6. HRMS (EI): m/z calcd for C₃₂H₃₃NO₂ [M⁺]: 463.2511; found: 463.2519.