New Entry to α,β-Unsaturated Lactams
bered lactam 6g in 66% yield [Equation (5)]. The six-mem- known to react with transition metals, further reactions
bered lactam 15g was, however, also obtained in 7% yield such as oligomerization of allenes were not observed in this
concomitantly. When the isolated compound 6g was sub- system.[2,13]
jected to the same reaction conditions as of Equation (5)
no isomerization to 15g occurred. In the case of carbamose-
Experimental Section
lenoate 5h, having a 5,6-heptadienyl group, both an eight-
membered lactam 6h and a seven-membered lactam 15h
were formed in low yields with poor selectivity even when
20 mol-% catalyst was used [Equation (6)].[12] As described
above (see Scheme 1), desired medium-sized lactams 6g–h
are formed through (σ-allyl)palladium species 17a by car-
bopalladation of the distal double bond of the allenes. Car-
bopalladation of the proximal double bond, giving car-
bonyl-chelated vinyl palladium complexes like 17b, is a pos-
sible pathway that leads to minor products 15g–h. Product
ratio would be determined by the relative stabilities of 17a
and 17b (Figure 2).
1-Benzyl-3-(phenylselenomethyl)-1,5-dihydropyrrol-2-one (6a). Typi-
cal Procedure: Into a 3-mL flask equipped with a reflux condenser
were placed carbamoselenoate 5a (0.41 mmol, 140 mg), DMF
(0.4 mL) and Pd(PPh3)4 (0.020 mmol, 24 mg) at room temperature
under N2, and the solution turned immediately red. After the mix-
ture was heated at 80 °C for 5 h, filtered through a Celite pad with
Et2O, volatiles were removed in vacuo. The crude product was puri-
fied by preparative TLC (n-hexane/Et2O, 1:1) to afford 6a in 90%
yield (126 mg) as brown oil. 1H NMR (400 MHz, CDCl3): δ = 3.65
(s, 2 H), 3.75 (s, 2 H), 4.62 (s, 2 H), 6.47 (s, 1 H) 7.19–7.51 (m, 10
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.3, 46.4, 50.0, 127.4,
127.6, 128.0, 128.7, 129.0, 130.0, 133.7, 136.4, 136.5, 137.2,
170.1 ppm. IR (NaCl): ν = 3060, 2917, 1682 (C=O), 1452, 1244,
˜
1077, 817, 738, 693 cm–1. MS (EI): m/z (%) = 343 (2) [M+], 185
(40), 91 (100). HRMS (EI): calcd. for C18H17NOSe 343.0475; found
1
343.0478. Copies of H and 13C NMR spectra of 6a in CDCl3 are
shown in the Supporting Information.
Supporting Information (see footnote on the first page of this arti-
cle): Experimental and calculation details and characterization data
of all new compounds.
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Acknowledgments
This work was supported by a Grant-in-Aid for Scientific Research
on Priority Areas “Advanced Molecular Transformations of Car-
bon Resources” from the Ministry of Education, Culture, Sports,
Science and Technology, Japan. M. T. expresses his special thanks
for JSPS Research Fellowship for Young Scientist for financial sup-
port and The Global COE (center of excellence) Program “Global
Education and Research Center for Bio-Environmental Chemistry”
of Osaka University.
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[4] To the best of our knowledge, only one example of Pd-cata-
lyzed intramolecular additions of allyl acetate to allene was
reported: T. Doi, A. Yanagisawa, S. Nakanishi, K. Yamamoto,
T. Takahashi, J. Org. Chem. 1996, 61, 2602–2603.
[5] For pharmacological activity of α,β-unsaturated lactams, see:
a) A. K. Mandal, J. Hines, K. Kuramochi, C. M. Crews, Bio-
Figure 2. Possible intermediates.
Conclusions
We report that intramolecular selenocarbamoylation of
allenes proceeds in the presence of Pd0 catalyst producing
α,β-unsaturated γ- and δ-lactams with perfect regioselectiv-
ity. This cyclization could also be applied to thiocarbamoyl-
ation and to the construction of a cyclopentenone frame-
work. Intramolecular addition of carbon–selenium bonds
to the allene unit takes place selectively giving rise to the
formation of allyl selenides. Although allyl selenides are
Eur. J. Org. Chem. 2009, 3141–3144
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