FANARI & SETAMDIDEH, Orient. J. Chem., Vol. 30(2), 695-697 (2014)
697
Our next attempt was the reduction of
ketones to the corresponding secondary alcohols.
The reduction of ketones was also obtained
successfully by 2 molar equivalents of Zn(BH4)2
under ultrasonic irradiation within 60-120 min at
room temperature in CH3CN with excellent yields of
the products (90-94%) (Table 1, entries 8-14).
equipped with a magnetic stirrer bar, a solution of
benzaldehyde (0.1061 g, l mmol) was prepared in
CH3CN (3 mL). To this solution Zn(BH4)2 (0.095 g,
1mmol) was added.The resulting mixture was stirred
under ultrasonic waves at room temperature for 5
min. The progress of the reduction reaction was
monitored by TLC (eluent:CCl4/Et2O:5/2). After
completion of the reaction, distilled water (5 mL)
was added to the reaction mixture and stirred for 5
min. The mixture was extracted with CH2Cl2 (3×10
mL) and dried over anhydrous Na2SO4. Evaporation
of the solvent afforded pure benzyl alcohol (0.102
g, 95% yield).
Also, we have examined the reduction of
cinnamaldehyde (Table 1, entry 7) and
benzalacetone (Table 1, entry 11) as models for a,b-
unsaturated aldehydes and ketones. The reduction
reactions took place to their corresponding allylic
alcohols in excellent yields in CH3CN at room
temperature as shown in scheme 2.
CONCLUSION
EXPERIMENTAL
In this context, we have shown that
Zn(BH4)2 under ultrasonic irradiation as new
reducing system is convenient for the reduction of
aldehydes and ketones to their corresponding
alcohols. Also, , -unsaturated aldehydes and
ketones are regioselectively reduced to the
corresponding allylic alcohols. The reduction
reactions were carried out with Zn(BH4)2 (1-2mmol)
in CH3CN at room temperature. Short reaction times
and easy work-up procedure makes as an attractive
new protocol for the reduction of carbonyl
compoundsto their corresponding alcohols.
Sonication was performed by using a
Bendeline uw 3100 (Germany) high intensity
ultrasonic (600 W, 20 KHz) via a micro-tip probe (vs
1
70t) and 70% amplitude. IR and H NMR spectra
were recorded on Perkin-Elmer FT-IR RXI and 300
MHz Bruker spectrometers, respectively. The
products were characterized by their 1H NMR or IR
spectra and comparison with authentic samples.
TLC was applied for the purity determination of
substrates, products and reaction monitoring over
silica gel 60 F254 aluminum sheet.
ACKNOWLEDGEMENTS
Typical procedure for the reduction of carbonyl
compounds with Zn(BH4)2 under ultrasonic
irradiation in CH3CN
The authors gratefully appreciated the
financial support of this work by the research council
of Islamic Azad University branch of Mahabad.
In a round-bottomed flask (10 mL)
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