Lingjuan Zhang et al.
COMMUNICATIONS
2.98–3.03 (m, 1H), 3.15–3.20 (m, 1H), 3.23–3.28 (m, 1H),
3.30–3.34 (m, 1H), 6.37 (s, 1H, OH), 7.19 (t, J=7.5 Hz,
1H), 7.27 (t, J=7.5 Hz, 2H), 7.32 (d, J=7.5 Hz, 2H), 7.36
(s, 1H), 7.39 (d, J=8.0 Hz, 2H), 8.10 (d, J=8.0 Hz, 2H)
11.7 (s, 1H, NH); 13C NMR (DMSO-d6, 125 Hz): d=36.4,
37.0, 74.8, 118.8, 123.2, 124.3, 126.0, 126.9, 127.8, 127.9,
128.5, 130.3, 133.1, 135.3, 141.9, 150.9, 159.4, 181.9; HR-MS
+
(ESI-TOF): m/z=426.0388, calcd for C22H17ClNO2S2 ([M+
Scheme 5. Synthesis of cyclopenta[b]pyrroles 3q and 3r.
H]+): 426.0384.
were prepared in excellent yields, respectively
(Scheme 5).
Acknowledgements
Finally, it should be emphasized that a comparison
of the present work (Table 1, Scheme 2 and
Scheme 5) with previous results shows the significant-
ly different performance between TosMIC and ethyl
isocyanoacetate. The reaction of alkenoyl ketene di-
thioacetals 1 with ethyl isocyanoacetate gave fused
oxazolines via a base-catalyzed tandem Michael addi-
tion/intramolecular isocyanide [3+2]cycloaddition, in
which the cycloaddition involves the terminal carbon-
yl group behaving as the dipolarophile [Scheme 1,
(A)].[8] In contrast, the terminal carbonyl carbon of 1
is acting as an electrophilic center to trap the initially
formed imidoyl anion species in the present work
(Scheme 4).
Financial support of this research provided by the NNSFC
(21072027) and the Young Scientific Research Foundation of
Jilin Province (20090149) is greatly acknowledged.
References
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In conclusion, a variety of cyclopenta[b]pyrroles
was synthesized in high to excellent yields under ex-
tremely mild and metal-free conditions from simple
acyclic precursors in a single step. This tandem bicy-
ACHTUNGTRENNUNGclization reaction exhibits not only a highly efficient
use of the reactive sites in the substrates, but also a
new application of methyl isocyanides through intra-
molecular trapping of the incipient imidoyl anion spe-
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ꢀ
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formed on the isocyanide carbon atom in a single
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Experimental Section
General Procedure for the Synthesis of 3 (3a as
Example)
To the solution of 1a (386 mg, 1.0 mmol) and tosylmethyl
isocyanide 2 (215 mg, 1.1 mmol) in DMF (10 mL) was added
NaOH (4.4 mg, 1.1 mmol) in one portion. The reaction mix-
ture was stirred at room temperature until 1a was consumed
as indicated by TLC. The resulting mixture was then poured
into brine (30 mL) under stirring. The solid was collected by
filtration, washed with water (3ꢂ10 mL), and dried under
vacuum to afford the crude product, which was purified by
flash chromatography on silica gel (petroleum ether/
EtOAc=6:1) to give 3a as a yellowish solid; yield: 387 mg
(91%); mp 193–1958C. 1H NMR (DMSO-d6, 500 Hz): d=
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2622
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2011, 353, 2619 – 2623