FULL PAPERS
The reaction is not limited to terminal alkenes of this
class, but also works very well for internal 1-aryl alkenes.
For example, b-methyl styrene reacts in a clean manner to
give the corresponding vicinal diamine as the only product
(entries 13,14). While the E isomer 1m leads to the (2S,3R/
2R,3S)-product, the opposite (2R,3R/2S,3S)-diastereomer is
formed as the major product from oxidation of the corre-
sponding Z isomer 1n (ratio 2n/2m=2.65:1). The relative
configuration of 2m was unambiguously assured from X-ray
analysis (Figure 1).[20]
which was insoluble and thus led to dramatically reduced
conversion. Attempts to accelerate the reaction through ad-
ditives were not successful, and finally, this problem could
be overcome by employing microwave irradiation. Under
such conditions, clean diamination of styrenes was accom-
plished, although for some styrenes the reaction time had to
be significantly increased.
Para-substituted styrenes are preferred substrates (en-
tries 3–10), and several substituents are tolerated, which in-
clude the benzyl chloride derivative (entry 5). In two cases,
it was found that thermal conditions could compete well
with microwave irradiation (entries 6,8). As expected, meta-
substitution proceeds equally well (entries 11–13). It is par-
ticularly interesting to note that with bismesylimide as nitro-
gen source, diamination of ortho-substituted styrenes pro-
ceeds readily (entries 14,15), probably due to the lower
steric demand of the bismesylimide in comparison to bisto-
sylimide.
The advantage of the bismesyl substitution is evident
from its convenient deprotection. Thus, single treatment
with sodium bis(2-methoxyethoxy)aluminumhydride (Red-
Al) leads to complete removal of all four mesyl substituents
within a single step. While the work-up readily provides the
free diamines, conversion into the corresponding bisbenza-
mides was found to be more convenient with regard to char-
acterization (Table 3). In total, the reported two-step proce-
dure includes the manipulation or formation of six amide
bonds and proceeds with excellent overall yields of 69–95%.
In summary, 1-aryl ethylenediamines are now available
through a rapid, productive diamination of the respective
styrenes in a robust low-step approach.
Figure 1. Crystal structure of 2m. C gray, S light gray, N dark gray, O
black, hydrogen white. Except for the stereogenic centers, hydrogen
atoms are omitted for clarity.
Despite the broad scope of the presented diamination re-
actions of styrenes (Tables 1 and 2), substrates displaying
high electron density such as para-methoxystyrene usually
lead to formation of enimides. This is particularly the case
Symmetric (E)-stilbenes 1o and 1p yield the correspond-
ing meso derivatives as single isomers (entries 15,16). A
slightly higher reaction temperature is required for this class
of substrates in order to reach full conversion within less
than 24 hours. Attempts to carry out the diamination of (Z)-
stilbene led again to formation of the meso product (50%
isolated yield), probably due to a rapid isomerization of the
double bond under the reaction conditions. However, chiral
diamine products can be obtained from the oxidation of un-
symmetrically substituted stilbenes such as 1q (entry 17).
The same process can be conducted with bismesylimide as
nitrogen source as well. Table 2 shows representative exam-
ples of this diamination reaction. It was noticed that the
mixture of iodosobenzene diacetate and bismesylimide led
for the oxidation with PhI
4a as the only isolated product (74% isolated yield). By
contrast, the combination of PhI(OAc)2 with HNMs2 gives
ACHTUGNRTEN(NUGN OAc)2/HNTs2, which resulted in
AHCTUNGTRENNUNG
the desired diamine 2y in 20% yield as the minor product.
The major product is again the elimination product 4b,
which is obtained in 72% yield (Scheme 1), providing
a 3.6:1 ratio of the enimide to the diamine product.
Intermolecular diamination of terminal alkenes 5 that do
not contain an aryl substituent has so far remained elusive
except for one report on palladium catalysis.[19a] Again, the
simple reagent combination of bissulfonimide and PhI-
to the quick formation of PhI
A
ACHTUNGRTEN(NGNU OAc)2 provides convenient access to this type of transfor-
mation, although a reaction temperature of 508C is re-
quired. Since bismesylimide results in diamine products
lacking any UV activity, exploration on the scope of this
transformation is carried out with bistosylimide (Table 4).
Hydrocarbons such as 1-hexene, 1-octene, 1-decene, and 1-
dodecene all give the corresponding diamines 6a–d as the
only oxidation products in very good yields (entries 1–4), as
does the a-branched vinylcyclohexane 5e (entry 5). For
octane 5b the reaction was scaled up to a 5 mmol reaction,
which again proceeded in a straight-forward manner to pro-
Abstract in Spanish: Se presenta un mꢄtodo eficiente y
rꢀpido para llevar a cabo la diaminaciꢅn de alquenos pro-
movido por especies de iodoACTHNURGTNE(NUG III) hipervalente en presencia
de bissulfonilimidas. Una serie de mas de 60 olefinas, tanto
en posiciꢅn terminal como interna, con distinta sustituciꢅn
demuestran la robustez del mꢄtodo y la elevada tolerancia
a grupos funcionales.
1104
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2012, 7, 1103 – 1111