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DOI: 10.1055/s-2002-32948
A Facile Access to the 1,5-Dihydro- and 1,3,4,5-Tetrahydro-benzo[b]azepin-2-one Ring Systems via a New Ring Enlargement
Publication History
Publication Date:
25 July 2002 (online)
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Abstract
Synthesis of a 1,5-dihydro-benzo[b]azepin-2-one is reported. The key reaction is a silver nitrate-induced rearrangement of N-benzyl quinolinium bromide. Its reduction leads to the 1,3,4,5-tetrahydro-benzo[b] azepin-2-one ring system found in several pharmacological important compounds.
Key words
quinolinium salt - silver nitrate - 1,5-dihydro-benzo[b]azepin-2-one - 1,3,4,5-tetrahydro-benzo[b] azepin-2-one - ring enlargement
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References
Spectral Data for
Compound 5:
IR (KBr): 1659, 1615, 1595 cm-1. 1H
NMR (200 MHz, CDCl3): δ = 3.40
(s, 3 H, OCH
3), 4.82 (br s,
1 H, CHOCH3), 5.08 and 5.40
(AB system, J = 15.2
Hz, 2 H, NCH
2), 5.84 (d, J = 11.2 Hz,
1 H, COCH=CH), 6.51 (dd, J = 11.2 and
4.0 Hz, 1 H, COCH=CH), 7.05-7.45
(m, 9 H, Ar). 13C NMR (50 MHz, CDCl3): δ = 52.4,
57.7, 77.2, 121.3, 122.6, 123.1, 125.7, 127.3, 127.4, 127.5 (2 C),
128.5 (2 C), 137.7, 138.3 (2 quaternary carbons), 146.1, 166.5.
MS: m/z (relative intensity) = 279(8) [M+],
264(19), 246(30), 91(100), 65(18). HRMS (SIMS) calcd for C18H17NO2 + H:
280.1338; found: 280.1342.
For a close example of Beckmann rearrangement, see ref. [2b]
13
Spectral Data
for Compounds 9 and 10:
9:
IR (KBr): 1667 cm-1. 1H
NMR (200 MHz, CDCl3): δ = 1.70-1.90
(m, 1 H, CH
2CHOCH3),
2.15-2.35 (m, 2 H, CH
2CO),
2.45-2.65 (m, 1 H, CH
2CHOCH3),
3.06 (s, 3 H, OCH
3), 4.01
(dd, J = 10.4
and 6.8 Hz, 1 H, CHOCH3),
4.63 and 5.37 (AB system, J = 14.4
Hz, 2 H, NCH
2), 7.10-7.35 (m,
9 H, Ar). 13C NMR (50 MHz, CDCl3): δ = 31.8,
35.4, 51.3, 57.6, 77.5, 123.3, 124.6, 126.7, 127.5, 128.1, 128.5
(4 C; the ortho and meta carbons of the phenyl ring are identical),
135.9, 137.6, 140.5, 172.6. MS: m/z (relative intensity) = 281(24) [M+],
194(58), 130(100), 91(90), 65(22). HRMS (SIMS) calcd for C18H19NO2 + H:
282.1494; found: 282.1491.
10:
IR (KBr): 1674 cm-1; 1H
NMR (200 MHz, CDCl3): δ = 2.00-2.20
(m, 1 H of the CH2CH2 motif), 2.30-2.60
(m, 3 H of the CH2CH2 motif), 3.32 (s, 3 H,
OCH
3), 3.70-3.85 (m,
1 H, CHOCH3), 4.90 and 5.24
(AB system, J = 14.8
Hz, 2 H, NCH
2), 7.05-7.30
(m, 9 H, Ar). 13C NMR (50 MHz, CDCl3): δ = 27.8,
36.2, 51.8, 57.9, 78.1, 123.1, 126.7, 127.5, 127.8, 128.3 (2 C),
128.5 (2 C), 129.1, 136.1, 137.6, 140.7, 171.6. MS: m/z (relative intensity) = 281(96) [M+],
132(79), 118(76), 91(100), 65(20). HRMS (SIMS) calcd for C18H19NO2 + H:
282.1494; found: 282.1495.