Enantioselective Organocatalytic Synthesis of Oxazolidine Derivatives
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the substituents on the phenyl ring of the cinnamyl al-
dehydes had little effect on the ee value but did
impact the total yields greatly. The electron-donating
group substituted cinnamyl aldehydes generally af-
forded highly yielded products while the electron-
withdrawing group often resulted in only moderate
yields. However, all the products were obtained with
high ee values, regardless of the properties of the sub-
stituents either on the vinyl aldehydes 2 or the aryl
amides 1.
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The absolute configuration of the isolated major
diastereoisomer 3m was determined by X-ray analysis
of a single crystal[14] (Figure 1), which was identical to
our predicted model (Figure 2) based on previous
work by Jørgensen,[15] Franzꢁn[8] and Rios.[16]
In summary, an easy one-pot cascade reaction
which afforded an oxazolidine derivative in a highly
enantioselective manner and moderate to good yield
with good to excellent diastereomeric ratio has been
developed. Further applications of this approach to-
wards the preparations of more complex enantioen-
riched compounds are currently being investigated.
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Experimental Section
Typical Procedure: (2R,3S,4aS)-Methyl 1-Oxo-3-
phenyl-1,2,3,4,4a-pentahydrobenzo[d]pyrido
ACHTUNGTNER[NUNG 2,1-
b]oxazole-2-carboxylate (3a)
A solution of methyl 3-(2-hydroxyphenylamino)-3-oxopro-
panoate 1a (0.4 mmol) in CH2Cl2 (0.4 mL) was stirred at
À208C for 5 min whereupon the solution of catalyst A
(0.04 mmol) and cinnamyl aldehyde (0.6 mmol) in CH2Cl2
(0.4 mL) was added. After that the reaction mixture had
been stirred at À208C until 1a disappeared (determined by
TLC), TsOH·H2O (0.8 mmol) was then added into the mix-
ture in one portion. After 10 min, the reaction mixture was
allowed to warm to room temperature and was stirred over-
night. Finally the reaction mixture was separated by column
chromatography with petroleum ether:ethyl acetate=10:1
as eluant to give the pure product 3a as white crystals;
yield: 90%. For more details, see Supporting Information.
Acknowledgements
We acknowledge National Natural Science Foundation of
China (20902018), the Fundamental Research Funds for the
Central
Universities,
Shanghai
Pujiang
Program
(08J1403300) and 111 project (B07023) for financial support.
References
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