decided to test aromatic amines (Table 2, entries 14–16), also
prolonging the reaction time to 24 h, the yields were low or the
reaction did not take place at all.
With these good results in hand, we also explored secondary
amines. In this case, the steric hindrance of the alkyl groups of
the amines influenced the reaction: N,N-diisopropylamine did
not react (Table 3, entry 2) and N,N-dibenzylamine was less
reactive (Table 3, entry 3), while less hindered secondary amines
gave very good yields.
Anyway in view of these good results, we applied the protocol
to bifunctional amines, to check the chemoselectivity of the
methodology and the results are given in Table 4.
This methodology is able to distinguish between an aromatic
and benzyl amine, operating only on this last functionality;
in fact when we used 2-aminobenzylamine, we obtained only
2-aminobenzylacetamide (Table 4, entry 1).
As shown in Table 4 (entries 2–7), when both hydroxy and
amino groups are present in the substrate, the methodology
selectively acetylates the amino group demonstrating the mild-
ness of the acetylation process.
Concerning entry 7 in Table 4, the remaining part of the
crude product was the starting amino alcohol (yield 40%),
but allowing the reaction to stand for 24 h at 60 °C, the yield of
N-butyl-2-hydroxyethylacetamide 7g increased up to 100%.
Finally, we have also investigated the acetylation of
1,2-aminothiophenol and 1,2-aminophenol but both compounds
did not react.
Acknowledgements
This work was financially supported by MIUR and CNR, Rome,
Italy. We thank Mr M. Di Pilato for his contribution to the exper-
imental part of this work.
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3. Conclusions
All the experimental results show that isopropenyl acetate is a
safe, cheap and readily available acetyl source under solvent-
and catalyst-free conditions and with operational simplicity.
Isopropenyl acetate is a prototype example of green reagent,
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4. Experimental section
In a typical procedure, in a capped vessel isopropenyl acetate
(4 mmol) and a suitable amine (1 mmol) were mixed. The reac-
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round-bottomed flask and concentrated under reduced pressure
in order to eliminate isopropenyl acetate in excess and acetone,
obtaining the crude product. This was analyzed by 1H and
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