Direct construction of a quaternary carbon center utilizing an organosamarium reagent

Article abstract of DOI:10.1016/S0040-4039(01)01831-7

Direct geminal diallylation of lactams and acyclic amides containing an N-H bond has been achieved in the presence of allylsamarium bromide. By applying this method, quaternary carbons have been constructed, and 2,2-diallylated nitrogen heterocycles and d

Full text of DOI:10.1016/S0040-4039(01)01831-7

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 8507–8510
Direct construction of a quaternary carbon center utilizing an
organosamarium reagent
Zhifang Lia and Yongmin Zhanga,b,
*
aDepartment of Chemistry, Zhejiang University (Campus Xixi ), Hangzhou 310028, PR China
bState Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, PR China
Received 15 August 2001; accepted 28 September 2001
Abstract—Direct geminal diallylation of lactams and acyclic amides containing an NꢀH bond has been achieved in the presence
of allylsamarium bromide. By applying this method, quaternary carbons have been constructed, and 2,2-diallylated nitrogen
heterocycles and diallylated amides were synthesized in moderate to good yields under mild conditions. © 2001 Elsevier Science
Ltd. All rights reserved.
The addition of allylic organometallics to carbonyl
compounds is an important synthetic method for the
construction of carbonꢀcarbon bonds.1 Usually,
homoallylic alcohols are obtained utilizing these meth-
ods, and little attention has been paid to the geminal
diallylation of carbonyl compounds.2 We have shown
that nitriles undergo reductive diallylation on treatment
with allylsamarium bromide to give the corresponding
diallylamides.3 However, to the best of our knowledge,
transformations of lactams and acyclic amides contain-
ing an NꢀH bond under the action of allylsamarium
bromide has not been investigated. Lukesˇ reported that
the reaction of RMgX with five- to eight-membered
lactams led to a mixture of 1-alkyl-1-aza-2-cyclenes and
2,2-dialkylated (arylated) heterocycles,4 and the reac-
tion of 2-piperidone with allylmagesium bromide led to
room temperature, 2,2-diallylated nitrogen heterocycles
(3) were obtained in good yields (Scheme 1). All runs
were completed within 5 min. The lactams and allylsa-
marium bromide were used in a ratio of 1:2.2 (mol).
It should be noted that when lactams, such as 2-pyrro-
lidinone, 2-piperidone, piperazinone and caprolactam,
were used in this reaction, the corresponding diallylated
nitrogen heterocycles were obtained in excellent yields
(Table 1).7 But when o-phthalimide (4) and succinimide
(5) were treated with allylsamarium bromide under the
same conditions, the diallylated compounds were not
detected at all, with 3-[(Z)-2-propenylidene]-1-isoindoli-
none (6) and 5-[(Z)-2-propenylidene]-2-pyrrolidinone
(7) being obtained, respectively (Scheme 2).
a
compound of unknown structure (C14H23N).5
It is interesting that acyclic amides (8) containing an
NꢀH bond can also react with allylsamarium bromide
to give the analogous diallylated amines (9)8 in moder-
ate to good yields (Scheme 3). The reaction conditions
and scope of this reaction are shown in Table 2.
Recently, Bubnov described the synthesis of 2,2-dially-
lated nitrogen heterocycles by the reaction of allylic
boranes with lactams under harsh conditions.6 We
report herein the geminal diallylation of lactams and
acyclic amides containing an NꢀH bond with allylsa-
marium bromide to construct quaternary carbons
directly.
When lactams (1) containing an NꢀH bond were
treated with allylsamarium bromide (2) in THF at
Keywords: samarium; allyl bromide; lactams; acyclic amides; 2,2-dial-
lylated nitrogen heterocycles; diallylated amides; reductive diallyla-
tion.
* Corresponding author. E-mail: yminzhang@mail.hz.zj.cn
Scheme 1.
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(01)01831-7

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Z. Li, Y. Zhang / Tetrahedron Letters 42 (2001) 8507–8510
Table 1. The reaction of lactams with allylsamarium bromide
the same conditions, the expected compound (9h) could
not be detected. When benzamide (10) was treated with
allylsamarium bromide, the diallyl carbinol (11) was
isolated in moderate yield (Scheme 4).
A possible mechanism of this reductive diallylation of
lactams and acyclic amides containing an NꢀH bond is
shown in Scheme 5. First, lactams (A) undergo allyla-
tion leading to intermediates (B), which eliminate the
HOSmBr fragment to produce imines (C). Imines (C)
immediately undergo allylation to form the intermedi-
ates (D), which were decomposed by water to produce
the desired diallylation products (E).
In summary, quaternary carbons are constructed
efficiently from lactams and acyclic amides containing
an NꢀH bond utilizing allylsamarium bromide. By
applying this method, 2,2-diallylated nitrogen heterocy-
cles and analogous diallylated amides are obtained
under mild conditions, which contain two double bonds
and a NH function and can be used for the preparation
of various derivatives such as bicyclic- and spiro-
compounds.
Scheme 2.
As shown in Table 2, acyclic amides (8) containing an
NꢀH bond undergo the diallylation reaction smoothly,
and the diallylated amides (9) were obtained in moder-
ate to good yields. But when N,N-diethylbenzamide
was treated with allylsamarium bromide for 10 h under

Z. Li, Y. Zhang / Tetrahedron Letters 42 (2001) 8507–8510
8509
Scheme 4.
Scheme 3.
Table 2. The reaction of acyclic amides with allylsamarium bromide
Entry
R1
R2
R3
Time (h)
Yielda (%)
a
b
c
d
e
f
g
h
i
CH3
C6H5
C6H5
H
H
H
H
H
H
H
2
3
4
3
3
4
4
10
3
75
75
75
70
65
50
50
0b
60
CH3CH2
CH3CH2
CH3CH2
C6H5
C6H5
p-CH3C6H4
C6H5
p-ClC6H4
o-CH3C6H4
CH2C6H5
p-CH3C6H4
C6H5
CH3CH2
H
CH3CH2
H
C6H5
a Isolated yields based on acyclic amides.
b The expected compound 9h could not be detected.
Scheme 5.
Acknowledgements
therein; (b) Lukesˇ, R.; Smolek, K. Coll. Czech. Chem.
Commun. 1939, 11, 506; (c) Lee, J.; Ziering, A.; Heineman,
S. D.; Berger, L. J. Org. Chem. 1947, 12, 885.
5. Lukesˇ, R.; Cerny, M. Coll. Czech. Chem. Commun. 1961,
26, 2886.
6. Bubnov, Y. N.; Pastukhov, F. V.; Yampolsky, I. V.;
We are grateful to the National Natural Science Foun-
dation of China (Project No.29872010) and the NSF of
Zhejiang province for financial support.
Ignatenko, A. V. Eur. J. Org. Chem. 2000, 1503.
7. General procedure: Samarium (0.33 g, 2.2 mmol) and allyl
bromide (0.30 g, 2.5 mmol) in THF (20 mL) were added to
a three-necked flask with stirring at room temperature
under nitrogen. When the color of the mixture turned
purple, stirring was continued for 1 h until the samarium
powder disappeared, then lactams or acyclic amides (1
mmol) were added to the solution, and the mixture was
stirred at room temperature for the appropriate times
(Tables 1 and 2). Water (5 mL) was added and the
reaction mixture extracted with diethyl ether (3×10 mL),
the diethyl ether solution washed with saturated NH4Cl
(2×10 mL) and dried over anhydrous MgSO4. The solvent
was removed by evaporation under reduced pressure. The
crude product was purified by preparative TLC on silica
gel (cyclohexane–ethyl acetate (3:1) as eluent).
References
1. (a) Hoffman, R. W. Angew. Chem., Int. Ed. Engl. 1982, 21,
555; (b) Yamamoto, Y.; Maruyama, K. Heterocycles 1982,
18, 357; (c) Yamamoto, Y. Acc. Chem. Res. 1987, 20, 243;
(d) Yamamoto, Y.; Asao, N. Chem. Rev. 1993, 93, 2207
and references cited therein.
2. Kataoka, Y.; Makihira, I.; Akiyama, H.; Tani, K. Tetra-
hedron 1997, 53, 9525.
3. Yu, M.-X.; Zhang, Y.-M.; Gou, H.-Y. Synth. Commun.
1997, 27, 1495.
4. (a) Lukesˇ, R.; Dudek, V.; Sedlakova, O.; Koran, I. Coll.
Czech. Chem. Commun. 1961, 26, 1105 and references cited

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Z. Li, Y. Zhang / Tetrahedron Letters 42 (2001) 8507–8510
8. Typical physical data for compounds 3a, 6e and 9a. Com-
(2H, m, CH2); MS m/z (%): 172 (M++1, 2.03), 171 (M+,
5.47), 130 (100), 102 (34.15). Anal. calcd for C11H9NO: C,
77.19; H, 5.26; N, 8.19. Found: C, 77.16; H, 5.20; N,
8.18%.
1
pound 3a (2,2-diallylpyrrolidine): bp 86–88°C (13 torr); H
NMR (400 MHz, CDCl3): l 5.76 (2H, m, 2×CH), 5.15
(4H, m, 2×CH2), 3.02 (2H, t, J=6.78 Hz, CH2N), 2.38
(4H, d, J=7.27 Hz, 2×CH2), 1.45–1.70 (5H, m, 2×CH2
+NH); MS m/z (%): 152 (M++1, 2.33), 151 (M+, 4.78), 110
(100). Anal. calcd for C10H17N: C, 79.41; H, 11.33; N,
9.26. Found: C, 79.39; H, 11.29, N, 9.29%.
Compound 9a (N-(1-allyl-1-methyl-3-butenyl)-N-phenyl-
amine): oil; IR (wmax): 3410 (NH), 2977, 1639 (RCHꢁCH2),
1
1601 cm−1; H NMR (400 MHz, CDCl3): l 7.11–7.21 (2H,
m, ArH), 6.71–6.73 (3H, m, ArH), 5.81–5.87 (2H, m,
2×CH), 5.05–5.11 (4H, m, 2×CH2), 3.49 (1H, br, NH),
2.30–2.47 (4H, m, 2×CH2), 1.27 (3H, s, CH3); MS m/z (%):
202 (M++1, 6.72), 201 (M+, 4.03), 160 (100), 118 (61.75),
77 (27.68). Anal. calcd for C14H19N: C, 83.58; H, 9.45; N,
6.96. Found: C, 83.56; H, 9.42, N, 6.94%.
Compound 6e (3-[(Z)-2-propenylidene]-1-isoindolinone):
mp 98–101°C; IR (wmax): 3320 (NH), 1700 (CꢁO), 1650,
;
1615 (CꢁC) cm−1 1H NMR (400 MHz, CDCl3): l
9.52 (1H, br s, NH), 7.89–7.27 (4H, m, ArH), 6.81–6.85
(1H, m, CH), 6.23 (1H, d, J=11.48 Hz, CH), 4.88–5.45