COMMUNICATIONS
Ruthenium Complex-Catalyzed Domino Addition/exo-Cycloisomerization
(21421004), NCET (NCET-13-0798), the Basic Research Pro-
gram of the Shanghai Committee of Sci. & Tech. (Project No.
13M1400802) and the Fundamental Research Funds for the
Central Universities.
gylic alcohol 2 and tosyl isocyanate gives the propar-
gylic carbamate 4. The alkyne group of intermediate
4 is activated by the ruthenium complex 1 to form an
h2-alkyne complex A, which rapidly undergoes intra-
molecular nucleophilic attack to give the ruthenium
complex B. Subsequently, Protonation of the metal–
carbon bond simultaneously releases oxazolidinone 3 References
and regenerates ruthenium complex 1. Comparing
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ACHTUNGTRENNUNG
demonstrates a much larger steric hindrance effect,
which is unfavorable for the addition to a ruthenium
vinylidene intermediate. Moreover, N-tosylamide pos-
sesses a stronger nucleophilicity to fulfil an intramo-
lecular nucleophilic attack to the h2-alkyne complex
A. Both factors may result in the exo-selectivity of
the current reaction.
In summary, we have developed the first ruthenium
complex-catalyzed protocol for producing oxazolidi-
nones in good to excellent yield via domino addition/
exo-cycloaddition between propargylic alcohol and
tosyl isocyanate. Mechanistic studies suggest that
during the reaction, propargylic alcohol and tosyl iso-
cyanate first undergo addition, generating propargylic
carbamate, which undergoes exo-cycloisomerization
exclusively to afford the oxazolidinone. The exo-selec-
tivity of complex 1 in the cycloisomerization of prop-
argylic carbamates contrasts with its endo-selectivity
in the cycloisomerization of alkynols, which demon-
strates the diverse catalytic abilities of ruthenium
complex 1. We hope our work will open the door to
an even broader array of catalytic applications of
ruthenium complex 1 in organic reactions.
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Experimental Section
[5] K. A. Jo, M. Maheswara, E. Yoon, Y. Y. Lee, H. Yun,
Typical Procedure for Ruthenium Complex 1-
Catalyzed Domino Addition/exo-Cycloisomerization
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4-Methylbenzenesulfonyl isocyanate (0.5 mmol) was added
to a solution of propargylic alcohol 2 (0.5 mmol) in toluene
or MeCN (1.5 mL, as indicated in Table 2). After the reac-
tion mixture had been stirred for 10 min at room tempera-
ture, the ruthenium complex 1 (0.01 or 0.025 mmol as indi-
cated in Table 2) was added and the temperature was in-
creased to 808C. After stirring for 4–24 h, the reaction mix-
ture was concentrated and purified by flash column chroma-
tography on silica gel using petroleum ether-EtOAc as
eluent (in ratios ranging from 10:1 to 3:1), giving the desired
product 3.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Project Nos. 21172069, 21372072 and
21190033), the Science Fund for Creative Research Groups
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Adv. Synth. Catal. 0000, 000, 0 – 0
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