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Fig. 2 Reusability studies of Ti catalyst. Reaction conditions: ani-
saldehyde (2 mmol), saccharin (2.4 mmol), TBHP (6 mmol), 1,4-
ꢀ
b
dioxane, 90 C, 1 h; isolated yiled.
This methodology is amply demonstrated in the synthesis of
drugs namely ethenzamide 3s and moclobemide 7. Scheme 4
shows the single step synthesis of moclobemide, a reversible
inhibitor of monoamine oxidase A via N-alkylation of 3e with 6.
Fig. 2 shows the results on reusability studies. Ti-superoxide
catalyst was readily recovered quantitatively by simple ltration
and reused again at least for 3 cycles without the loss of catalytic
activity (runs 1–3). The catalyst performed under truly hetero-
geneous manner as no leaching of Ti was observed in the
aqueous part.
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In conclusion, we have described here a simple, convenient and
environment-friendly protocol for primary amide synthesis
directly from aldehydes using Ti-superoxide as a mild and
cheap catalyst and saccharin as amine source using TBHP as
oxidant. The presented strategy has several advantages that
include: (i) Ti catalyst is recyclable; (ii) good functional group
compatibility; (iii) wide range of substrate scope; (iv) mild
reaction conditions; (v) no additives and can be easily scaled up;
3
3
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(
vi) saccharin as cheaply available amine source. We envisage
that this new catalytic method would be used as an alternative
to other existing methods for the primary amide synthesis.
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Conflicts of interest
There are no conicts to declare.
724.
Acknowledgements
5
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RBK and KDM are grateful to CSIR-New Delhi, India while BDR
thanks UGC-New Delhi for the award of senior research
fellowships.
Notes and references
1
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