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Synlett 2012; 23(16): 2375-2380
DOI: 10.1055/s-0032-1317148
letter
© Georg Thieme Verlag Stuttgart · New York

Vanadium-Catalyzed Oxidation of tert-Butyl N-Hydroxycarbamate to tert-Butyl Nitrosoformate and Its Diels–Alder Reaction with Simple and Functionalized Dienes

Yujiro Hoshino*
Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan, Fax: +81(45)3394434   Email: yhoshino@ynu.ac.jp
,
Kenzo Suzuki
Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan, Fax: +81(45)3394434   Email: yhoshino@ynu.ac.jp
,
Kiyoshi Honda
Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan, Fax: +81(45)3394434   Email: yhoshino@ynu.ac.jp
› Author Affiliations
Further Information

Publication History

Received: 12 June 2012

Accepted after revision: 26 July 2012

Publication Date:
13 September 2012 (online)

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Abstract

A general and efficient vanadium-catalyzed oxidation of tert-butyl N-hydroxycarbamate to tert-butyl nitrosoformate using alkyl hydroperoxides as terminal oxidants has been developed. The intermediate nitroso compound was trapped by in situ Diels–Alder reaction with simple and functionalized dienes, providing general access to a variety of functionalized 3,6-dihydro-2H-1,2-oxazines.

Key words

nitroso Diels–Alder reaction - catalysis - oxidation - functionalized dienes - vanadium catalyst

Supporting Information

    for this article is available online at http://www.thieme-connect.com/ejournals/toc/synlett.
  • Supporting Information
 

  • References and Notes

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  • 14 N-tert-Butoxycarbonyl-2-oxa-3-azabicyclo[2.2.1]hept-5-ene (2b) 16 TLC: Rf  = 0.33 (hexane–Et2O = 1:2). IR (neat): 2978, 1739, 1702, 1165 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.47 (s, 9 H), 1.73 (d, J = 8.6 Hz, 1 H), 1.99 (td, J = 2.4, 8.6 Hz, 1 H), 4.98 (br s, 1 H), 5.21 (br s, 1 H), 6.40–6.42 (m, 2 H). N-tert-Butoxycarbonyl-2-oxa-3-azabicyclo[2.2.2]oct-5-ene (2c) 16 TLC: Rf  = 0.51 (hexane–EtOAc = 3:1). IR (neat): 2976, 2936, 1736, 1695, 1158, 1073 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.27–1.54 (m, 2 H), 1.47 (s, 9 H), 2.06–2.23 (m, 2 H), 4.73–4.75 (m, 2 H), 6.50–6.59 (m, 2 H). (3S*,6R*)-N-tert-Butoxycarbonyl-3,6-diphenyl-3,6-dihydro-2H-1,2-oxazine (2d) TLC: Rf  = 0.39 (hexane–EtOAc = 5:1). IR (neat): 2978, 1700, 1392, 1368, 1166, 1094, 699 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.49 (s, 9 H), 5.56 (br s, 1 H), 5.59 (br s, 1 H), 6.09 (d, J = 10.5 Hz, 1 H), 6.16 (ddd, J = 10.8, 4.5, 2.1 Hz, 1 H), 7.26–7.53 (m, 10 H). 13C NMR (75 MHz, CDCl3): δ = 28.4, 79.0, 81.7, 126.4, 127.7, 127.8, 128.2, 128.5, 128.7, 129.0, 137.2, 139.2, 154.2. N-tert-Butoxycarbonyl-1,8-dimethyl-15-oxa-16-azatetracyclo[6.6.2.02,7.09,14]hexadec-2,4,6,9,11,13-hexaene (2e) 4 Mp 106–109 °C. TLC: Rf  = 0.33 (hexane–EtOAc = 5:1). IR (KBr): 2981, 1707, 1460, 1288, 1159, 748 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.21 (s, 9 H), 2.23 (s, 3 H), 2.56 (s, 3 H), 7.23–7.27 (m, 4 H), 7.34–7.38 (m, 2 H), 7.43–7.46 (m, 2 H). A 1:1 Mixture of N-tert-Butoxycarbonyl-4-methyl-3,6-dihydro-2H-1,2-oxazine (2f) and N-tert-Butoxycarbonyl-5-methyl-3,6-dihydro-2H-1,2-oxazine (3f) 13 TLC: Rf  = 0.66 (hexane–EtOAc = 6:1). IR (neat): 2978, 2933, 1705, 1683, 1392, 1368, 1243, 1166, 1102 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.50 [s, 9 H, 3 × CH3 (3f)], 1.51 (s, 9 H, 3 × CH3), 1.67 [br s, 3 H, CH3-5 (3f)], 1.74 (br s, 3 H, CH3-4), 3.94 (br s, 2 H, H-3), 4.02–4.05 [m, 2 H, H-3 (3f)], 4.26 [br s, 2 H, H-6 (3f)], 4.35–4.38 (m, 2 H, H-6), 5.51–5.55 [m, 1 H + 1 H, overlapped with H-5 and H-4 (3f)]. A 1:1 Mixture of N-tert-Butoxycarbonyl-4-(4-methyl-pent-3-enyl)-3,6-dihydro-2H-1,2-oxazine (2g) and N-tert-Butoxycarbonyl-5-(4-methylpent-3-enyl)-3,6-dihydro-2H-1,2-oxazine (3g) TLC: Rf  = 0.64 (hexane–EtOAc = 6:1). IR (neat): 2976, 2929, 1727, 1703, 1366, 1162, 1092 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.50 (s, 9 H + 9 H), 1.60 (s, 3 H + 3 H), 1.69 (s, 3 H + 3 H), 1.98–2.12 (m, 4 H + 4 H), 3.97 (br s, 2 H), 4.05 (br s, 2 H), 4.29 (br s, 2 H), 4.39 (br s, 2 H), 5.05–5.12 (m, 1 H + 1 H), 5.52 (br s, 1 H + 1 H). 13C NMR (75 MHz, CDCl3): δ = 17.7, 25.6, 25.8, 25.9, 28.3, 32.7, 33.9, 44.9, 47.6, 68.0, 70.4, 81.4, 116.0, 117.6, 123.3, 132.3, 134.2, 135.5, 155.0. N-tert-Butoxycarbonyl-6-carboxy-3-methyl-3,6-dihydro-2H-1,2-oxazine (2h) TLC: Rf  = 0.68 (MeOH). IR (KBr): 2977, 1748, 1686, 1370, 1156, 1121 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.36 (d, J = 6.6 Hz, 3 H), 1.51 (s, 9 H), 4.43 (br s, 1 H), 5.16 (s, 1 H), 5.93–6.03 (m, 2 H). 13C NMR (75 MHz, CDCl3): δ = 17.9, 28.3, 50.8, 75.9, 82.8, 121.9, 130.6 154.5, 170.5. N-tert-Butoxycarbonyl-6-ethoxycarbonyl-3-methyl-3,6-dihydro-2H-1,2-oxazine (2i) 17 TLC: Rf  = 0.63 (hexane–EtOAc = 6:1). IR (neat): 2980, 1760, 1738, 1705, 1369, 1312, 1196, 1169, 1076, 1032, 716 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.32 (t, J = 7.1 Hz, 3 H), 1.36 (d, J = 6.8 Hz, 3 H), 1.50 (s, 9 H), 4.27 (q, J = 7.2 Hz, 2 H), 4.46–4.48 (m, 1 H), 5.14–5.16 (m, 1 H), 5.90 (td, J = 1.3, 10.4 Hz, 1 H), 5.98 (ddd, J = 10.2, 4.3, 2.5 Hz, 1 H). N-tert-Butoxycarbonyl-6-methoxycarbonyl-3-hydroxy-methyl-3,6-dihydro-2H-1,2-oxazine (2j) TLC: Rf  = 0.24 (hexane–EtOAc = 1:1). IR (neat): 3446, 2979, 1737, 1707, 1475, 1251, 1157, 1071, 1024 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.50 (s, 9 H), 3.73–3.88 (m, 2 H), 3.82 (s, 3 H), 4.51–4.55 (m, 1 H), 5.52 (s, 1 H), 6.00 (ddd, J = 10.2, 3.9, 2.1 Hz, 1 H), 6.06 (td, J = 1.5, 10.5 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 28.2, 52.8, 56.6, 63.0, 74.3, 82.8, 124.3, 125.7, 155, 167.6. N-tert-Butoxycarbonyl-3-[(triisopropylsilyloxy)methyl]-6-methoxycarbonyl-3,6-dihydro-2H-1,2-oxazine (2k) TLC: Rf  = 0.77 (hexane–EtOAc = 1:1). IR (neat): 2943, 2867, 1766, 1740, 1710, 1367, 1109, 881, 681 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.02–1.13 (m, 3 H), 1.06 (d, J = 3.9 Hz, 18 H), 1.49 (s, 9 H), 3.80 (s, 3 H), 3.82 (dd, J = 9.6, 7.8 Hz, 1 H), 3.97 (dd, J = 9.3, 6.6 Hz, 1 H), 4.48–4.49 (m, 1 H), 5.16–5.19 (m, 1 H), 6.02 (td, J = 1.8, 10.2 Hz, 1 H), 6.16 (ddd, J = 10.2, 4.2, 2.7 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 11.9, 17.9, 28.3, 52.6, 55.8, 64.1, 74.7, 82.1, 123.2, 127.3, 154.1, 167.9. N-tert-Butoxycarbonyl-6-(N′-methoxy-N′-methyl-carbamoyl)-3-methyl-3,6-dihydro-2H-1,2-oxazine (2l) TLC: Rf  = 0.25 (hexane–Et2O = 1:2). IR (neat): 3592, 2979, 2934, 1681, 1369, 1172, 992, 714 cm–1. 1H NMR (300 MHz, CDCl3): δ = 1.37 (d, J = 6.6 Hz, 3 H), 1.51 (s, 9 H), 3.24 (br s, 3 H), 3.84 (s, 3 H), 4.45–4.47 (m, 1 H), 5.53 (br s, 1 H), 5.86 (br s, 1 H), 5.99 (ddd, J = 10.5, 5.1, 2.4 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 17.9, 28.4, 32.4, 50.7, 62.2, 74.3, 81.7, 122.3, 130.0, 154.2. N-tert-Butoxycarbonyl-3-[(tert-butyldimethylsilyloxy)-methyl]-6-methoxycarbonyl-3,6-dihydro-2H-1,2-oxazine (2m) TLC: Rf  = 0.66 (hexane–EtOAc = 1:1). IR (neat): 2954, 2930, 2857, 1766, 1741, 1710, 1253, 1106, 834, 777 cm–1. 1H NMR (300 MHz, CDCl3): δ = 0.07 (s, 6 H), 0.89 (s, 9 H), 1.49 (s, 9 H), 3.73 (dd, J = 9.9, 7.2 Hz, 1 H), 3.81 (s, 3 H), 3.88 (dd, J = 10.2, 7.2 Hz, 1 H), 4.46 (br s, 1 H), 5.16–5.19 (m, 1 H), 6.01 (td, J = 1.5, 10.2 Hz, 1 H), 6.11 (ddd, J = 10.5, 4.2, 2.7 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = –5.3, –5.3, 18.2, 25.6, 25.8, 28.3, 52.6, 55.8, 63.6, 74.7, 82.1, 123.5, 127.0, 154.2, 167.8.
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