M. J. Palframan et al. / Tetrahedron Letters 47 (2006) 8423–8425
8425
chromatography to yield the pyrrolidinone 8a as a pale
yellow oil (63 mg, 37%); Rf 0.07 (petrol/ethyl acetate, 2:1);
m
would result based on the similar cases described by
Jones et al.15
max(thin film)/cmꢀ1 3448w, 2927s, 2360w, 1689s, 1515s,
1463s, 1400s; dH (400 MHz, CDCl3) 2.49 (1H, dd, J 17.0,
8.0 Hz, H3), 2.78 (1H, dd, J 17.0, 8.0 Hz, H3), 2.89 (3H, s,
NCH3), 3.35 (1H, dd, J 9.5, 7.0 Hz, H5), 3.48–3.57 (1H, m,
H4), 3.71 (1H, dd, J 9.5, 8.0 Hz, H5), 3.79 (3H, s, OCH3),
6.87 (2H, d, J 8.5 Hz, ArH), 7.14 (2H, d, J 8.5 Hz, ArH);
dC (100 MHz, CDCl3) 29.5 (NCH3), 36.5 (C4), 38.9 (C3),
55.3 (OCH3), 56.9 (C5), 114.2 (2 · ArCH), 127.7
(2 · ArCH), 134.5 (ArC), 158.5 (ArC–O), 173.9 (C@O);
m/z (CI+) 206 (MH+, 100%), 134 (45); HRMS found:
206.1188, C12H16NO2 (MH+) requires 206.1181.
7. Review: Studer, A.; Bossart, M. Tetrahedron 2001, 57,
9649–9667.
In summary, we have demonstrated the operation of
sequential radical 1,4-aryl migration and formal 5-
endo-trig cyclisation of 1-(arylcarboxamido)prop-2-
en-2-yl radicals in which the amide nitrogen bears an
alkyl group. In a future report, we will describe our
study of the synthesis and radical reactions of substrates
designed to address the limitations caused by rotameric
preferences about the amide group.
Acknowledgements
8. For a related example of b-scission of a spirocyclic lactam
to generate an amidoyl radical, see: Wang, S.-F.; Chuang,
C.-P.; Lee, J.-H.; Liu, S.-T. Tetrahedron 1999, 55, 2273–
2288.
We are grateful to the Chemistry Research Laboratory
NMR and MS staff for their assistance in structure
determination.
9. Review: (a) Ishibashi, H.; Sato, T.; Ikeda, M. Synthesis
2002, 695–713; see also the discussion in (b) Chatgilialo-
glu, C.; Ferreri, C.; Guerra, M.; Timokhin, V.; Froudakis,
G.; Gimisis, T. J. Am. Chem. Soc. 2002, 124, 10765–10772.
10. For pertinent studies see: (a) Bowman, W. R.; Westlake,
P. J. Tetrahedron 1992, 48, 4027–4038; (b) McNab, H. J.
Chem. Soc., Chem. Commun. 1990, 543–545; see also: (c)
Dowd, P.; Zhang, W. Chem. Rev. 1993, 93, 2091–2115.
11. Bottini, A. T.; Dev, V. J. Org. Chem. 1962, 27, 968–973.
12. Carrying out the reactions in refluxing benzene (80 ꢁC) or
chlorobenzene (136 ꢁC) did not change the ratios of
rearranged/reduced starting material.
References and notes
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13. 1,4-Hydrogen atom abstraction in both photochemical
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6. General conditions for radical cyclisation exemplified by
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inone (8a). To a stirred, degassed solution of amide 7a
(210 mg, 0.73 mmol) and AIBN (12 mg, 0.07 mmol) in
benzene (40 ml) at reflux was added a solution of Bu3SnH
(0.27 ml, 0.88 mmol) and AIBN (32 mg, 0.20 mmol) in
benzene (10 ml) over 4 h and the resulting mixture was
heated at reflux for a further 2 h and then concentrated in
vacuo. The crude product was eluted with dichlorometh-
ane through a stationary phase of KF (10%) impregnated
silica (Ref. 16) to remove tin residues followed by flash
14. Cohen, T.; McMullen, C. H.; Smith, K. J. Am. Chem. Soc.
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1969.