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A novel synthetic approach to 11-substituted dibenzo[b,f][1,4]oxazepines

  • Nilesh Zaware EMAIL logo and Michael Ohlmeyer
Published/Copyright: August 5, 2014
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Heterocyclic Communications
From the journal Heterocyclic Communications Volume 20 Issue 4

Abstract

A novel protocol for the synthesis of 11-substituted dibenzo[b,f][1,4]oxazepines is reported. Seven compounds were designed as analogs of the antipsychotic drug loxapine and antidepressant amoxapine. The key transformations include generation of a carbamate intermediate using phenyl chloroformate which avoids the use of harmful phosgene, a microwave-induced transformation of the carbamate intermediate into various urea derivatives, and a subsequent phosphorous oxychloride-induced cyclocondensation. The simple reactions and wide substrate scope enhance the practical application of this methodology.

Keywords: amoxapine; dibenzo[b,f][1,4]oxazepine; loxapine

Dibenzo[b,f][1,4]oxazepine derivatives possess diverse pharmacological activity [1–6]. Loxapine 1 and amoxapine 2 (Figure 1) are agents used for their antipsychotic and antidepressant action, respectively [7]. Both 1 and 2 bear the 11-substituted dibenzo[b,f][1,4]oxazepine scaffold.

Figure 1 Structures of loxapine and amoxapine.
Figure 1

Structures of loxapine and amoxapine.

We report a new method for synthesis of seven fused 11-substituted dibenzo[b,f][1,4]oxazepines, namely compounds 19–25 (Scheme 1). The compounds were designed as analogs of 1 and 2.

Scheme 1 Synthesis of 19–25.
Scheme 1

Synthesis of 19–25.

2-(4-Chlorophenoxy)aniline (3) was synthesized according to a reported method [8]. Previously reported synthetic approaches [9, 10] to 11-substituted dibenzo[b,f][1,4]oxazepines using 3 involve treating 3 with toxic phosgene or triphosgene to afford intermediate 1-(phenoxy)-2-isocyanatobenzene. We decided to avoid the use of phosgene or triphosgene by treating 3 with phenyl chloroformate under mild conditions, which afforded carbamate 4 in 98% yield. Compound 4 was heated with amines 5–11 in a microwave reactor to yield the respective urea derivatives 12–18. The yields of these transformations ranged from 79% to 96%. A phosphorous oxychloride-induced cyclocondensation of 12–18 furnished the target dibenzo[b,f][1,4]oxazepines 19–25, respectively, in yields ranging from 4% to 38%.

In conclusion, we have developed a novel methodology for synthesis of 11-substituted dibenzo[b,f][1,4]oxazepines. The simplicity of the experiments, wide substrate scope, and avoidance of toxic phosgene, makes this methodology a useful addition in the collection of 11-substituted dibenzo[b,f][1,4]oxazepine syntheses.

Experimental

Phenyl [2-(4-chlorophenoxy)phenyl]carbamate (4)

A solution of 2-(4-chlorophenoxy)aniline (2.00 g, 9.10 mmol) and pyridine (0.83 mL, 10.0 mmol) in ethyl acetate (17.0 mL) at 0°C was treated dropwise with phenyl chloroformate (1.22 mL, 10.0 mmol).

The resultant mixture was stirred for 3 h at room temperature. The solvent was removed under reduced pressure, and the residue was purified by silica gel flash chromatography eluting with 2% to 5% ethyl acetate-hexanes to afford phenyl [2-(4-chlorophenoxy)phenyl]carbamate 4 (3.02 g, 98%): 1H NMR (600 MHz, CDCl3) δ 8.26 (1H, bs), 7.56 (1H, bs), 7.41 (2H, t, J = 7.8 Hz), 7.35 (2H, d, J = 9.0 Hz), 7.31–7.30 (1H, m), 7.26 (1H, t, J = 7.2 Hz), 7.21 (2H, d, J = 7.8 Hz), 7.17 (1H, t, J = 7.8 Hz), 7.04 (1H, t, J = 7.2 Hz), 7.01 (2H, d, J = 8.4 Hz), 6.89 (1H, d, J = 8.4 Hz); 13C NMR (150 MHz, CDCl3) δ 155.2, 151.7, 150.7, 145.3, 130.2, 129.6, 129.2, 126.5, 126.0, 124.8, 123.9, 121.8, 121.1, 120.1, 118.0. ESI-HRMS. Calcd for C19 H15 ClNO3, [M++H+]: m/z 340.0735. Found: m/z 340.0733.

General procedure for synthesis of carboxamides 12–18

A solution of phenyl [2-(4-chlorophenoxy)phenyl]carbamate 4 (0.45 g, 1.3 mmol) in methanol (4.5 mL) was treated with amine (2.0 mmol). The mixture was heated at 100°C for 15 min in a Biotage Initiator® microwave reactor. The solvent was removed under reduced pressure, and the residue was purified by flash chromatography on silica gel eluting with 5% to 50% ethyl acetate-hexanes to afford the title compound as an oil.

N-[2-(4-Chlorophenoxy)phenyl]thiomorpholine-4-carboxamide (12)

Yield 82%; 1H NMR (600 MHz, CDCl3) δ 8.17 (1H, d, J = 8.4 Hz), 7.30 (2H, d, J = 9.0 Hz), 7.15 (1H, t, J = 7.2 Hz), 6.97 (1H, t, J = 9.0 Hz), 6.93 (2H, d, J = 9.0 Hz), 6.86–6.85 (2H, m), 3.72 (4H, t, J = 4.8 Hz), 2.58 (4H, t, J = 4.8 Hz); 13C NMR (150 MHz, CDCl3) δ 155.5, 154.0, 144.9, 131.1, 130.1, 128.9, 125.0, 123.1, 121.0, 119.3, 118.6, 47.2, 27.1. ESI-HRMS. Calcd for C17 H18 ClN2 O2 S, [M++H+]: m/z 349.0773. Found: m/z 349.0768.

N-[2-(4-Chlorophenoxy)phenyl]morpholine-4-carboxamide (13)

Yield 92%; 1H NMR (600 MHz, CDCl3) δ 8.19 (1H, d, J = 7.8 Hz), 7.28 (2H, d, J = 8.4 Hz), 7.12 (1H, t, J = 7.8 Hz), 6.96–6.91 (4H, m), 6.83 (1H, d, J = 7.8 Hz), 3.66 (4H, t, J = 4.8 Hz), 3.38 (4H, t, J = 4.8 Hz); 13C NMR (150 MHz, CDCl3) δ 155.4, 154.6, 145.1, 131.0, 130.1, 128.9, 124.9, 123.1, 121.0, 119.5, 118.3, 66.5, 44.2. ESI-HRMS. Calcd for C17 H18 ClN2 O3, [M++H+]: m/z 333.1001. Found: m/z 333.0995.

N-[2-(4-Chlorophenoxy)phenyl]piperidine-1-carboxamide (14)

Yield 84%; 1H NMR (600 MHz, CDCl3) δ 8.19 (1H, d, J = 8.4 Hz), 7.25 (2H, d, J = 9.0 Hz), 7.09 (1H, t, J = 7.8 Hz), 6.90–6.89 (4H, m), 6.83 (1H, d, J = 7.8 Hz), 3.33 (4H, t, J = 5.4 Hz), 1.57–1.56 (2H, m), 1.50–1.49 (4H, m); 13C NMR (150 MHz, CDCl3) δ 155.7, 154.5, 144.8, 131.7, 130.0, 128.6, 125.0, 122.6, 121.0, 119.2, 118.6, 45.3, 25.7, 24.5. ESI-HRMS. Calcd for C18 H20 ClN2 O2, [M++ H+]: m/z 331.1208. Found: m/z 331.1206.

N-{2-[3-(2-(4-Chlorophenoxy)phenyl)ureido]ethyl}benzenesulfonamide (15)

Yield 95%; 1H NMR (600 MHz, CDCl3) δ 8.05 (1H, d, J = 8.4 Hz), 7.73 (2H, d, J = 7.8 Hz), 7.49–7.46 (2H, m), 7.38 (2H, t, J = 7.8 Hz), 7.12 (2H, d, J = 8.4 Hz), 7.00 (1H, t, J = 7.8 Hz), 6.87 (1H, t, J = 7.8 Hz), 6.78 (2H, d, J = 9.0 Hz), 6.73 (1H, d, J = 7.8 Hz), 6.05–6.01 (2H, m), 3.24–3.23 (2H, m), 2.95 (2H, bs); 13C NMR (150 MHz, CDCl3) δ 156.3, 155.5, 145.4, 139.3, 132.9, 131.1, 129.8, 129.3, 128.5, 127.0, 124.6, 122.8, 120.7, 119.8, 118.3, 43.8, 39.8. ESI-HRMS. Calcd for C21 H21 ClN3 O4 S, [M++H+]: m/z 446.0936. Found: m/z 446.0928.

N-[2-(4-Chlorophenoxy)phenyl]-4-phenylpiperazine-1-carboxamide (16)

Yield 96%; 1H NMR (600 MHz, CDCl3) δ 8.26 (1H, d, J = 7.8 Hz), 7.31–7.27 (4H, m), 7.16 (1H, t, J = 7.8 Hz), 7.04 (1H, bs), 6.99–6.95 (3H, m), 6.91–6.87 (4H, m), 3.57 (4H, t, J = 5.4 Hz), 3.15 (4H, t, J = 5.4 Hz); 13C NMR (150 MHz, CDCl3) δ 155.6, 154.5, 151.0, 145.2, 131.2, 130.2, 129.4, 128.9, 125.0, 123.1, 121.2, 120.5, 119.5, 118.6, 116.6, 49.2, 44.1. ESI-HRMS. Calcd for C23 H23 ClN3 O2, [M++H+]: m/z 408.1474. Found: m/z 408.1466.

3-[2-(4-Chlorophenoxy)phenyl]-1,1-dimethylurea (17)

Yield 79%; 1H NMR (600 MHz, CDCl3) δ 8.21 (1H, d, J = 7.8 Hz), 7.19 (2H, d, J = 8.4 Hz), 7.05 (1H, t, J = 8.4 Hz), 6.87–6.84 (4H, m), 6.78 (1H, d, J = 7.8 Hz), 2.85 (6H, s); 13C NMR (150 MHz, CDCl3) δ 155.6, 155.2, 144.6, 131.7, 130.0, 128.5, 125.0, 122.6, 120.7, 119.1, 118.6, 36.3. ESI-HRMS. Calcd for C15 H16 ClN2 O2, [M++H+]: m/z 291.0895. Found m/z 291.0894.

N-[2-(4-Chlorophenoxy)phenyl]pyrrolidine-1-carboxamide (18)

Yield 80%; 1H NMR (600 MHz, CDCl3) δ 8.31 (1H, d, J = 8.4 Hz), 7.28–1.26 (2H, m), 7.13 (1H, t, J = 7.8 Hz), 6.94–6.91 (2H, m), 6.85 (1H, d, J = 8.4 Hz), 6.77 (1H, bs), 3.37 (4H, t, J = 6.6 Hz), 1.92–1.90 (4H, m); 13C NMR (150 MHz, CDCl3) δ 155.7, 153.7, 144.4, 131.6, 130.0, 128.6, 125.1, 122.5, 120.5, 119.1, 118.7, 45.9, 25.7. ESI-HRMS. Calcd for C17 H18 ClN2 O2, [M++H+]: m/z 317.1052. Found: m/z 317.1047.

General procedure for synthesis of 2-chloro-11-substituted dibenzo[b,f][1,4]oxazepines 19–25

A solution of carboxamide 12–18 (1 mmol) in phosphorus oxychloride (33.0 mL) was heated at reflux for 17 h. The phosphorus oxychloride was removed under reduced pressure and the residue was neutralized with ice water and ammonium hydroxide and extracted with dichloromethane. The extract was concentrated under reduced pressure, and the residue was purified by silica gel flash chromatography eluting with 10%–50% ethyl acetate-hexanes to afford the title compound.

2-Chloro-11-thiomorpholinodibenzo[b,f][1,4]oxazepine (19)

Yield 24% from 12; 1H NMR (600 MHz, CDCl3) δ 7.39 (1H, dd, J = 9.0 Hz and 2.4 Hz), 7.29–7.28 (1H, m), 7.19 (1H, t, J = 8.4 Hz), 7.13–7.07 (3H, m), 6.99 (1H, t, J = 7.2 Hz), 3.85 (4H, bs), 2.74 (4H, bs); 13C NMR (150 MHz, CDCl3) δ 159.4, 158.8, 151.9, 140.1, 132.8, 130.5, 129.0, 127.2, 126.0, 125.2, 124.8, 123.0, 120.2, 50.1, 27.2. ESI-HRMS. Calcd for C17 H16 ClN2 OS, [M++H+]: m/z 331.0667. Found: m/z 331.0661.

2-Chloro-11-morpholinodibenzo[b,f][1,4]oxazepine (20)

Yield 9% from 13; 1H NMR (600 MHz, CDCl3) δ 7.40 (1H, dd, J = 8.4, 1.8 Hz), 7.32 (1H, d, J = 2.4 Hz), 7.20–7.15 (2H, m), 7.11–7.08 (2H, m), 7.01 (1H, t, J = 7.2 Hz), 3.83 (4H, bs), 3.53 (4H, bs); 13C NMR (150 MHz, CDCl3) δ 159.6, 159.2, 152.0, 132.9, 130.5, 129.2, 127.3, 126.0, 125.0, 123.0, 120.3, 66.9, 48.3. ESI-HRMS: Calcd for C17 H16 ClN2 O2, [M++H+]: m/z 315.0895. Found: m/z 315.0890.

2-Chloro-11-piperidinodibenzo[b,f][1,4]oxazepine (21)

Yield 9% from 14; 1H NMR (600 MHz, CDCl3) δ 7.37 (1H, dd, J = 9.0, 3.0 Hz), 7.31 (1H, d, J = 3.0 Hz), 7.18 (1H, d, J = 8.4 Hz), 7.14 (1H, dd, J = 7.8, 1.8 Hz), 7.10–7.06 (2H, m), 6.96 (1H, td, J = 7.8, 1.8 Hz), 3.47 (4H, bs), 1.70 (6H, bs); 13C NMR (150 MHz, CDCl3) δ 159.5, 159.3, 152.0, 140.7, 132.4, 130.0, 129.2, 127.2, 125.9, 125.7, 124.2, 122.7, 120.1, 48.6, 26.0, 25.0. ESI-HRMS. Calcd for C18 H18 ClN2 O, [M++H+]: m/z 313.1103. Found: m/z 313.1102.

N-{2-[(2-Chlorodibenzo[b,f][1,4]oxazepin-11-yl)amino]ethyl}benzenesulfonamide (22)

Yield 38% from 15; 1H NMR (600 MHz, CDCl3) δ 8.77 (1H, bs), 8.37 (1H, bs), 7.62–7.58 (3H, m), 7.41 (2H, t, J = 7.8 Hz), 7.29 (2H, d, J = 9.0 Hz), 7.19–7.16 (1H, m), 7.02–6.99 (3H, m), 5.00 (1H, bs), 3.68 (4H, bs); 13C NMR (150 MHz, CDCl3) δ 156.2, 147.4, 144.3, 136.5, 134.0, 132.9, 131.9, 129.9, 129.6, 129.3, 128.3, 127.6, 126.5, 125.4, 123.2, 119.7, 118.7, 49.7, 47.0. ESI-HRMS. Calcd for C21 H19 ClN3 O3 S, [M++H+]: m/z 428.0831. Found: m/z 428.0824.

2-Chloro-11-(4-phenylpiperazino)dibenzo[b,f][1,4]oxazepine (23)

Yield 9% from 16; 1H NMR (600 MHz, CDCl3) δ 7.41 (1H, dd, J = 8.4, 2.4 Hz), 7.38–7.37 (1H, m), 7.31 (2H, t, J = 7.2 Hz), 7.22–7.19 (2H, m), 7.13–7.10 (2H, m), 7.03–6.99 (3H, m), 6.92 (1H, t, J = 7.2 Hz), 3.70 (4H, bs), 3.32 (4H, bs); 13C NMR (150 MHz, CDCl3) δ 159.6, 159.1, 152.0, 151.3, 140.2, 132.8, 130.5, 129.4, 129.3, 127.3, 126.0, 125.1, 124.9, 122.9, 120.5, 120.3, 116.7, 49.5, 47.6. ESI-HRMS. Calcd for C23 H21 ClN3 O, [M++H+]: m/z 390.1368. Found: m/z 390.1360.

2-Chloro-11-(dimethylamino)dibenzo[b,f][1,4]oxazepin-11-amine (24)

Yield 4% from 17; 1H NMR (600 MHz, CDCl3) δ 7.37 (1H, dd, J = 8.4, 2.4 Hz), 7.30 (1H, d, J = 2.4 Hz), 7.18 (1H, d, J = 8.4 Hz), 7.16 (1H, dd, J = 7.8, 1.8 Hz), 7.10–7.06 (2H, m), 6.95 (1H, td, J = 7.8, 1.2 Hz), 3.07 (6H, bs); 13C NMR (150 MHz, CDCl3) δ 159.4, 159.1, 151.8, 140.8, 132.3, 130.2, 129.4, 127.2, 125.9, 125.3, 124.0, 122.7, 120.1, 39.7. ESI-HRMS. Calcd for C15 H14 ClN2 O, [M++H+]: m/z 273.0790. Found: m/z 273.0787.

2-Chloro-11-(pyrrolidino)dibenzo[b,f][1,4]oxazepine (25)

Yield 7% from 18; 1H NMR (600 MHz, CDCl3) δ 7.36–7.34 (2H, m), 7.18–7.15 (2H, m), 7.10–7.06 (2H, m), 6.93–6.91 (1H, m), 3.64 (2H, bs), 3.49 (2H, bs), 2.03 (2H, bs), 1.90 (2H, bs); 13C NMR (150 MHz, CDCl3) δ 158.8, 157.1, 151.8, 141.3, 132.0, 130.0, 128.8, 127.2, 126.3, 126.0, 123.4, 122.4, 120.2, 49.2, 25.7. ESI-HRMS. Calcd for C17 H16 ClN2 O, [M++H+]: m/z 299.0946. Found: m/z 299.0943.

Corresponding author: Nilesh Zaware, Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, NY 10029, USA, e-mail: ;

Acknowledgments

Dual Therapeutics LLC and Grant #0249-1924 from BioMotiv LLC are gratefully acknowledged.

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Received: 2014-6-23
Accepted: 2014-6-25
Published Online: 2014-8-5
Published in Print: 2014-8-1

©2014 by De Gruyter

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Articles in the same Issue

  1. Frontmatter
  2. Preliminary Communication
  3. A novel synthetic approach to 11-substituted dibenzo[b,f][1,4]oxazepines
  4. Research Articles
  5. Cyclopropyl aziridines: solvolytic reactions of the N-tosylaziridines of (+)-2-carene and (+)-3-carene
  6. Synthesis and crystal structural characterization of two new 3,5-disubstituted 4-amino-1,2,4-triazoles
  7. A facile synthesis of 7,12-dihydro-1,3,6,7,12-pentaazapleiadenes by domino reaction
  8. New derivatives of 4,6-dimethylisoxazolo[3,4-b] pyridin-3(1H)-one: synthesis, tautomerism, electronic structure and antibacterial activity
  9. Synthesis and antimicrobial evaluation of purine substituted N-acyl-α-carboxamides via the Ugi four-component reaction
  10. Facile synthesis of substituted dihydro-1H-pyrazolo[3,4-d]thiazoles through enaminones of 4-thiazolidinones
  11. Multi-component synthesis of 1,2-diphenyl-2-[2-(5-aryl-6H-1,3,4-thiadiazin-2-yl)hydrazono]ethanone
  12. Ab initio study of mechanism of forming a spiro-Si-heterocyclic compound involving Ge from (CH3)2Ge=Si: and formaldehyde
https://doi.org/10.1515/hc-2014-0105
Keywords for this article
amoxapine; dibenzo[b,f][1,4]oxazepine; loxapine
Creative Commons
BY-NC-ND 3.0

Articles in the same Issue

  1. Frontmatter
  2. Preliminary Communication
  3. A novel synthetic approach to 11-substituted dibenzo[b,f][1,4]oxazepines
  4. Research Articles
  5. Cyclopropyl aziridines: solvolytic reactions of the N-tosylaziridines of (+)-2-carene and (+)-3-carene
  6. Synthesis and crystal structural characterization of two new 3,5-disubstituted 4-amino-1,2,4-triazoles
  7. A facile synthesis of 7,12-dihydro-1,3,6,7,12-pentaazapleiadenes by domino reaction
  8. New derivatives of 4,6-dimethylisoxazolo[3,4-b] pyridin-3(1H)-one: synthesis, tautomerism, electronic structure and antibacterial activity
  9. Synthesis and antimicrobial evaluation of purine substituted N-acyl-α-carboxamides via the Ugi four-component reaction
  10. Facile synthesis of substituted dihydro-1H-pyrazolo[3,4-d]thiazoles through enaminones of 4-thiazolidinones
  11. Multi-component synthesis of 1,2-diphenyl-2-[2-(5-aryl-6H-1,3,4-thiadiazin-2-yl)hydrazono]ethanone
  12. Ab initio study of mechanism of forming a spiro-Si-heterocyclic compound involving Ge from (CH3)2Ge=Si: and formaldehyde
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