yield (Scheme 2). The cleavage of the urazoles 3 was
performed by treatment with 3 N potassium hydroxide in
methanol at 80 °C. Under these conditions, the allylic ureas
4a-e and threo-4f were isolated in 58-72% yield. This
unusual transformation may be rationalized in terms of proton
abstraction at the methylene group in urazole 3 to give
carbanion 7 (Scheme 3). The ring opening of 7 to 8 is favored
obtained from the corresponding TAD ene adducts in up to
55% overall yields. Although this procedure entails a
multistep sequence, only the trialkylated urazoles 3 need to
be isolated; the remaining steps are conducted in a one-pot
process!
The treatment of the urazole 3b with 1 equiv of sodium
hydride under anhydrous conditions, followed by addition
of dimethyl sulfate, led to the 1,3,5-triazine-2,4-dione 6b in
80% yield (Scheme 2). Since only 1 equiv of base was
employed under anhydrous conditions, the acylimino inter-
mediate 8 does not afford the corresponding biuret derivative
9 (Scheme 3), but instead, intramolecular nucleophilic attack
is preferred to result in a six-membered ring of the anionic
1,3,5-triazinedione intermediate (not shown). Treatment with
dimethyl sulfate and in situ methylation at the amidate
nitrogen site afforded finally the triazinedione 6b (Scheme
3; route B).
Scheme 3
In conclusion, a new and effective tandem process, namely
TAD ene reaction followed by the novel carbanion-assisted
cleavage of the N-N urazole bond, has been developed for
the direct allylic amination of simple and functionalized
olefins. This method employs a one-pot, multistep procedure
in which only the trialkylated urazoles 3 need to be isolated.
Most significant, the diastereoselective and regioselective
TAD ene reaction with chiral allylic alcohols, i.e., mesitylol
(1f), permits the preparation of the functionalized threo-
configured allylic amine derivative threo-5f.
Acknowledgment. We thank the Deutsche Forschungs-
gemeinschaft (Schwerpunktprogramm: Sauerstofftransfer/
Peroxidchemie), the European Commission (postdoctoral
fellowship for A.P.), and the Fonds der Chemischen Industrie
(doctoral fellowship for T.W.) for financial support.
by the good leaving-group ability of the ureido fragment.
The latter is hydrolyzed under the reaction conditions, first
to a deprotonated biuret intermediate 9 and subsequently to
the urea 4 (Scheme 3; route A). The allylic amines 5a-e
and threo-5f were released from the in-situ-generated allylic
ureas 4 by hydrolysis with 50% solution of aqueous KOH;
first the mixture was heated at 80 °C and then at 155 °C in
a sealed tube for 6 h. The free amines were isolated as the
only products in 40-68% yield (Scheme 2).
Supporting Information Available: Complete experi-
mental procedures. This material is available free of charge
OL000044C
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