Mild and high-yielding molybdenum(VI) dichloride dioxide-catalyzed formation of Mono-, Di-, Tri-, and tetracarbamates from alcohols and aromatic or aliphatic isocyanates

Article abstract of DOI:10.1002/adsc.201200303

Both molybdenum(VI) dichloride dioxide (MoO₂Cl₂) and its dimethylformamide (DMF) complex catalyze the addition of alcohols to isocyanates giving carbamates. Most additions proceeded to completion at room temperature within 20 min using as little as 0.1 mol% of the catalyst when working on a 1-mmol scale or just 100 ppm working on a 20-mmol scale. Sterically encumbered substrates reacted to completion when 1 mol% of the catalyst was employed. Diols, triols, and tetraols reacted with monoisocyanates likewise, as did monofunctional alcohols and diisocyanates. These pairings furnished di-, tri-, tetra-, and dicarbamates, respectively. Reactants, which were poorly soluble in CH₂Cl₂ at room temperature required elevating the temperature and possibly choosing a higher-boiling solvent (ClCH ₂CH₂Cl, DMF) as well. Additions of diols to diisocyanates were feasible, too, giving polycarbamates as we presume. Copyright

Full text of DOI:10.1002/adsc.201200303

FULL PAPERS
DOI: 10.1002/adsc.201200303
Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-
Catalyzed Formation of Mono-, Di-, Tri-, and Tetracarbamates
from Alcohols and Aromatic or Aliphatic Isocyanates
Christian Stocka and Reinhard Brꢀcknera,*
a
Institut fꢀr Organische Chemie und Biochemie, Albert-Ludwigs-Universitꢁt Freiburg, Albert-Straße 21, 79104 Freiburg,
Germany
Fax : (+49)-761-203-6100; e-mail: reinhard.brueckner@organik.chemie.uni-freiburg.de
Received: April 14, 2012; Revised: June 20, 2012; Published online: && &&, 0000
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201200303.
Abstract: Both molybdenum(V) dichloride dioxide and diisocyanates. These pairings furnished di-, tri-,
(MoO2Cl2) and its dimethylformamide (DMF) com- tetra-, and dicarbamates, respectively. Reactants,
plex catalyze the addition of alcohols to isocyanates which were poorly soluble in CH2Cl2 at room tem-
giving carbamates. Most additions proceed to com- perature required elevating the temperature and pos-
pletion at room temperature within 20 min using as sibly choosing a higher-boiling solvent (ClCH2CH2Cl,
little as 0.1 mol% of the catalyst when working on DMF) as well. Additions of diols to diisocyanates
a 1-mmol scale or just 100 ppm working on a 20- were feasible, too, giving polycarbamates as we pre-
mmol scale. Sterically encumbered substrates reacted sume.
to completion when 1 mol% of the catalyst was em-
ployed. Diols, triols, and tetraols reacted with monoi- Keywords: carbamoylation; heterocumulenes; mo-
socyanates likewise, as did monofunctional alcohols lybdenum(vi); ureas; urethanes
Introduction
is mostly conducted in the presence of a promoter or
a catalyst. The considerable array of Brønstedt bases,
Esters of carbamic acids - for which we will use the Brønstedt acids, and Lewis acids, which have been
shorthand designation “carbamates” rather than “ure- used in this regards was detailed in ref.[17]. Still, sever-
thanes” – are an important class of compounds. By al of these established promoters/catalysts require the
their annual production the leading carbamates are use of excess alcohol and/or an elevated temperature,
high-performance macromolecules. They stem from particularly for sterically hindered substrates. This
the addition of polyether-based or polyester-based may lead to side-product formation, that is, to yield
multifunctional alcohols to a diisocyanate.[1] Oligocar- losses and to a need to purify the crude product.
bamates make up peptidomimetics[2] up to the size of
unnatural biopolymers.[3] Taxoterꢂ, which is market-
ed by Sanofi-Aventis for the treatment for breast, Results and Discussion
prostate, and lung cancer, is a semisynthetic carba-
mate of the natural product paclitaxel and twice as cy- During an ongoing project we had to add alcohol 1 to
totoxic as the latter.[4] The maytansinoids[5] and disco- the moderately reactive aryl isocyanates 2–5
dermolide[6] are carbamate-containing anti-tumor (Table 1). The OH group was prone to heat-, base- or
agents, too. In crop protection carbamates serve as in- acid-induced b-eliminations under many conditions.
secticides.[7] Carbamates are not only synthetic tar- Additionally, products 6–9 proceeded to react as an
gets[8] but are also used as O-nucleophiles,[9] N-nucleo- N-nucleophile by an intramolecular Michael addition
philes,[10] protective groups[11] and radical progeni- to the enoate moiety. These difficulties limited the
tors.[12] Moreover, carbamates serve as lithiation-di- yield of our initial carbamate synthesis 1+2!6 to
recting groups,[13] chiral auxiliaries[14], constituents of 83% after 7.5 h at 408C in the presence of 10 mol%
transition metal complexes[15] and linkers.[16]
of NEt3. We found that 5.0 mol% of DMAP[18] al-
The standard synthesis of a carbamate is by the ad- lowed us to add alcohol 1 to N-phenyl isocyanate (2)
dition of an alcohol to an isocyanate.[8] This reaction within 2.7 h at room temperature and also in 83%
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Table 1. DMAP- vs. Mo(VI)-catalyzed addition of alcohol 1 to aryl isocyanates 2–5.
Entry
Rpara
H
Isocyanate
Catalyst
Time [h]
Yield[a]
Carbamate
1[b]
2
3
2
DMAP
MoO2Cl
DMAP
MoO2Cl
DMAP
MoO2Cl
DMAP
MoO2Cl
2.7
1.0
17
3.2
2.3
1.5
3.0
1.3
83%
98%
88%
98%
83%
quant.
85%
quant.
6
(DMF)2
OMe
Ac
3
4
5
7
8
9
4
E
5
6[c]
7
CHTUNGTRENNUNG
Br
8[c]
CHTUNGTRENNUNG
[a]
Isolated yield after aqueous work-up and flash-chromatography.
PhNCO (1.1 equiv.).
[1]0 =0.15M.
[b]
[c]
yield (Scheme 3, entry 1).[19] This result was essentially ordinary efficient catalysts for realizing such addi-
satisfactory – had there not been an over-reaction: tions.[17] Using 1 mol% of MoO2Cl
2A(DMF)2 rather
CTHUNGTRENNUNG
Excess isocyanate 1 underwent an ArSE substitution than 5 mol% of DMAP before and cutting back the
in the phenyl moiety of carbamate 6, attacking para reaction time from 2.7 h to 1 h increased the yield of
to the nitrogen substituent. The resulting amide, carbamate 6 from 83% to 98% (Table 1, entry 2 vs.
whose formula is not shown, was difficult to separate 1). Concomitantly, the amide-delivering over-reaction
from the desired carbamate 6 by flash-chromatogra- of excess isocyanate 2 with 6, which we had observed
phy on silica gel.[20]
in the DMAP-catalyzed carbamoylation no longer in-
The acetylation of alcohols, amines, or thiols by terfered. Similar time savings (ꢁ~50%) and yield im-
acetic anhydride is catalyzed by MoO2Cl2.[21] This provements (+~15%) were noted for analogous car-
finding was rationalized by an attack of the oxygen bamate formations from the alcohol 1 and the aryl
terminus of the indicated Cl2(O=)Mo=O$Cl2(O= isocyanates 3–5 when we used MoO2Cl
CHTUNGTERNN(UNG DMF)2 in-
ꢀ
y
ꢁ
)Mo
pair Cl2(O=)Mo OAc·OAc . Bond formation be- vs. 7).
ꢀ
y
ꢁ
tween the oppositely charged centers would lead to
Motivated by these steps forward we explored the
2A(DMF)2-
ꢁ
Cl2(O=)Mo
( OAc)2. This addition product of acetic scope of MoO2Cl2-catalyzed and MoO2Cl
anhydride to a Mo=O bond of the catalyst was sug- catalyzed carbamate syntheses from alcohols and iso-
gested to be the effective acetylating agent. What if the cyanates. We began by optimizing the reaction be-
C
aryl isocyanates 2–5 were attacked by the oxygen ter- tween (ꢁ)-menthol (10) and phenyl isocyanate (2) as
ꢀ
ꢁ
minus of the indicated Cl2(O=)Mo=O$Cl2(O=)Mo
model reactants (Table 2). At room temperature we
Oy bond of MoO2Cl2 in a similar fashion? Such an in- added 1.2 equiv. of isocyanate 2 to a mixture of alco-
teraction of the isocyanate with MoO2Cl2 would deliv- hol 10 (c0 =0.3M) and 1.0 mol% of MoO2Cl2 in
er an “inner ion-pair” as an intermediate. If this CH2Cl2 (entry 1). An exothermic reaction started im-
“inner ion-pair” continued to react similarly as mediately and subsided after a few minutes. Aqueous
Cl2(O=)Mo OAc·OAc , namely by bond formation work-up of the reaction mixture after 20 min afforded
between the oppositely charged centers an addition the carbamate 11 as a pure compound (as judged by
product of the isocyanate to an Mo=O bond of the its 400 MHz 1H NMR spectrum in CDCl3) in quantita-
catalyst would result.[22] We hoped that it would be an tive yield.[26,27] The catalyst loading could be de-
ꢀ
y
ꢁ
effective carbamoylating agent.
creased from 1 mol% (entry 1) to 0.5 mol% and
While the foregoing reasoning may have been erro- 0.1 mol% without any significant yield losses (en-
neous it led to a pleasing result. Both MoO2Cl2 and tries 2 and 3). With regard to the last mentioned reac-
[23,24,25]
the complex MoO2Cl
(DMF)2
derived there- tion it should be noted that there the carbamate 11
from by precipation from an ethereal solution upon was isolated by flash-chromatography on silica gel.[20]
addition of 2.1 equiv. of DMF turned out to be extra-
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
Scheme 1 and Scheme 2.[17] They comprise the addi-
tion of alcohols 12–17 to phenyl isocyanate (2), the
addition of (ꢁ)-menthol (10) to the isocyanates 3, 4,
and 18–21, and the addition of tert-butanol (16) to
tert-butyl isocyanate (21). The resulting carbamates
are depicted in the center line (22–27) of Scheme 1,
and in the bottom line (28–33) of Scheme 1, and as
compound 34 in Scheme 2, respectively. The primary
alcohols 12–14 gave carbamates 22–24 in quantitative
yields.[26] The secondary alcohol cyclohexanol (15) fur-
nished 95% of carbamate 25. The addition of tert-bu-
tanol (16) to phenyl isocyanate (2) required 1.0 mol%
of catalyst to give carbamate 26 in 98% yield. In
order to obtain as much carbamate 27 from a,a-dime-
thylpropargyl alcohol (17) the initial concentration of
the alcohol had to be increased to 5.0M. The sterical-
ly hindered (ꢁ)-menthol (10) added to aryl isocya-
nates 3 and 4 rendering the carbamates 28 and 29, re-
spectively, in quantitative yields.[26] The additions of
(ꢁ)-menthol (10) to the primary alkyl isocyanates,
namely butyl isocyanate (18) or benzyl isocyanate
(19), gave the carbamates 30 and 31 in 98% and
quantitative yield, respectively.[26] (ꢁ)-Menthol (10)
Table 2. Decreasing the amount of MoO2Cl2 or MoO2Cl2
ACHTUNGTRENNUNG
Entry
Catalyst
mol%
Yield[a]
catalyst
1
2
3
1
quant.[26]
99%
MoO2Cl2
0.5
0.1
0.1
0.01
98%[b]
4
quant.[26]
quant.[26]
MoO2Cl2ACHTNUGRTENUNG(DMF)2
5[c]
[a]
All reactions provided carbamate 11 in analytically pure
form after aqueous work-up and removal of the solvent.
Yield after purification by flash-chromatography.
[10]0 =1.0M.
[b]
[c]
Even then we isolated the carbamate 11 in 98% yield. and cyclohexyl isocyanate (20) yielded the carbamate
This confirms the cleanness of our reaction.
32 in 90% yield. The addition of (ꢁ)-menthol (1) to
MoO2Cl2A(DMF)2 was an equally effective catalyst tert-butyl isocyanate (21) afforded the sterically con-
CHTUNGTRENNUNG
as MoO2Cl2 for the formation of carbamate 11 from gested carbamate 33 in quantitative yield, if the cata-
(ꢁ)-menthol (10) and phenyl isocyanate (2; Table 2, lyst loading was increased to 1 mol% and the reaction
entry 4) In contrast to MoO2Cl2, which was a fluffy time to 2 h.[26] The most sterically hindered reactant
powder, MoO2Cl
For this reason a predetermined mg-amount of butyl isocyanate (21). Catalyzed by 1.0 mol% of
MoO2Cl2A(DMF)2 could be charged into a reaction MoO2Cl2A(DMF)2 the N,O-di-tert-butyl carbamate 34
flask more easily. On the other hand MoO2Cl2A(DMF)2 was formed in 93% yield after 2 h (Scheme 2).
was as sparingly soluble in CH2Cl2 as MoO2Cl2. Dicarbamates (Scheme 3, Scheme 4, Scheme 5), tri-
Therefore, once in the flask it was finely ground with carbamates (Scheme 6), and tetracarbamates
a magnetic stirring bar. Our intent was to increase the (Scheme 6) were accessible from MoO2Cl2A(DMF)2-
rate of dissolution of MoO2Cl2A(DMF)2 thereby. This catalyzed alcohol/isocyanate reactions in high yields,
2ACHTUNGTNER(NUNG DMF)2 consisted visibly of crystals. combination consisted of tert-butanol (16) and tert-
C
CHTUNGTRENNUNG
CTHUNGTRENNUNG
CTHUNGTRENNUNG
CTHUNGTRENNUNG
procedure even allowed us to lower the catalyst load- too.
ing to 100 ppm and to isolate – after 20 min – carba-
In the dicarbamate syntheses of Scheme 3 ethanol
mate 11 still in a quantitative yield[26] (entry 5). Ad- (35), (ꢁ)-menthol (10), and tert-butanol (16) were
mittedly in the last experiment the initial alcohol con- added to diisocyanates, which are used for the pro-
centration was 1.0M as opposed to 0.3M before.
The scope of our optimized reaction conditions (TDI, 36), 4,4’-methylenediphenyl diisocyanate (MDI,
{0.1 mol% of MoO2Cl2A(DMF)2, [alcohol]0 =1.0M, 37) and isophorone diisocyanate (IPDI, 38; cis,trans
work-up after 20 min} was explored in some depth. mixture). In the cases of ethanol and (ꢁ)-menthol
First, we studied further mono-carbamate syntheses, 0.1 mol% of MoO2Cl2A(DMF)2 (with respect to the al-
duction of polyurethanes: 2,4-toluene diisocyanate
CTHUNGTRENNUNG
CTHUNGTRENNUNG
varying the alcohol and the isocyanate as shown in cohol;=0.2 mol% with respect to the diisocyanate)
Scheme 1 and Scheme 2.[17] Secondly, we added mono- sufficed to bring about virtually complete conversions.
valent alcohols to diisocyanates, obtaining the dicar- This entailed doubling the reaction time for the steri-
bamates depicted in Scheme 3. Thirdly, we combined cally most hindered reactant combination, i.e., (ꢁ)-
diols with monoisocyanates, which provided the dicar- menthol (10) plus IPDI (38). tert-Butanol (16) re-
bamates specified in Scheme 4 and Scheme 5. Using quired catalyst loadings of 1.0 mol% (with respect to
triols and tetraols as nucleophiles and monovalent the alcohol;=2.0 mol% with respect to the diisocya-
isocyanates as electrophiles, we prepared the tricarba- nate) for achieving yields ꢂ95%.
mates and tetracarbamates compiled in Scheme 6.
In the dicarbamate syntheses of Scheme 4 we
Monocarbamate syntheses under the conditions switched roles by adding diols of increasing sterical
specified in the preceding paragraph are shown in demand to phenyl isocyanate (2) and tert-butyl isocya-
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Scheme 1. MoO2Cl
(DMF)2-catalyzed monocarbamate syntheses I: Addition of alcohols 12–17 to phenyl isocyanate (2; !
carbamates 22–27) and of (ꢁ)-menthol (10) to isocyanates 3, 4, and 18-21 (!carbamates 28–33). Each carbamate was ob-
tained in analytically pure form after aqueous work-up and removal of the solvent.
nate (21). These diols were octane-1,8-diol (48), 2,2- quantitative yield of dicarbamate 52) but as fast as
dimethylpropane-1,3-diol (49), and 2,5-dimethylhex- octane-1,8-diol (48) to isocyanate 21 (30 min; !98%
ane-2,5-diol (50). A mixture of the least hindered diol dicarbamate 55).[26] These are observations of gross
48, phenyl isocyanate (2), and 0.2 mol% (relative to events, not determinations of rate constants.[28]
the diol) MoO2Cl
G
A successful addition of 2,5-dimethylhexane-2,5-
and solidified after 3 min. Aqueous work-up after diol (50) to phenyl isocyanate (2; Scheme 4) called
10 min delivered the dicarbamate 51 analytically pure for three modifications of our standard procedure.
in quantitative yield.[26] The addition of diol 48 to tert- Firstly, more catalyst had to be employed (2.0 mol%).
butyl isocyanate (21) was a bit slower requiring Secondly, DMF had to be the solvent. Thirdly, the re-
1.0 mol% of catalyst to yield 98% of dicarbamate 54 action temperature had to be increased to 608C. The
after 30 min. The neopentylic hydroxy groups of 2,2- two latter adaptations were crucial for obtaining, after
dimethylpropane-1,3-diol (49) added more slowly 1 h, 98% of the dicarbamate 53 in spite of the poor
than octane-1,8-diol (48) to isocyanate 2 (60 min; ! solubility of the diol. The bis-tertiary alcohol 50 and
tert-butyl isocyanate (21) delivered the sterically most
hindered dicarbamate 56 of Scheme 4 in CH2Cl2 in
94% yield. Admittedly, this required reflux tempera-
ture for 4 h and the usage of 2.0 mol% (relative to
the diol) MoO2Cl2ACHTUNTGRENUNG(DMF)2. The same conditions had
been inapplicable to the addition of the same diol 50
to phenyl isocyanate (2; see above).
We studied dicarbamate formation from diethanol-
amine (59) and selected monoisocyanates, too
(Scheme 5). The difference between this diol and
Scheme 2. MoO2Cl2ACHTUNGTRENNUNG(DMF)2-catalyzed monocarbamate syn-
theses II: Addition of tert-butanol (16) to tert-butyl isocya-
nate (21).
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
Scheme 3. MoO2Cl2ACHTUNGTRENNUNG(DMF)2-catalyzed dicarbamate syntheses I: Addition of alcohols 10, 16 and 35 to diisocyanates 36–38.
Scheme 4. MoO2Cl2ACHTUNGTRENNUNG(DMF)2-catalyzed dicarbamate syntheses II: Addition of diols 48–50 to phenyl isocyanate (2) and tert-
butyl isocyanate (21).
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Scheme 5. MoO2Cl2ACHTUNGTRENNUNG(DMF)2-catalyzed dicarbamate syntheses III: MoO2Cl2CAHTUNGTRNE(NUGN DMF)2-catalyzed tricarbamoylations (right)
versus uncatalyzed N-monocarbamoylations (left) of diethanolamine (59) by additions to phenyl isocyanate (2; top) or tert-
butyl isocyanate (21; bottom). Urea formation is spontaneous while carbamate formation follows only in the presence of the
catalyst (the mol% of which is referred to 59).
Scheme 6. MoO2Cl2ACHTUNGTRENNUNG(DMF)2-catalyzed tri- and tetracarbamate syntheses: Addition of triol 62 and tetraol 63 to phenyl isocya-
nate (2) and tert-butyl isocyanate (21).
diols 48–50 from Scheme 4 is that the nitrogen atom ethanolamine (59) in CH2Cl2 resulted in clean forma-
constitutes a third nucleophile. In the absence of a cat- tions of the corresponding 3:1 adducts (Scheme 5).
alyst, N-carbamoylation was observed, giving the Thereby, the urea-containing dicarbamate 58 became
ureas 57 (quantitative yield[26]) and 60 (88% yield), re- accessible after 30 min in 97% yield. The more steri-
spectively. None of these urea formations was accom- cally hindered, equally urea-containing dicarbamate
panied by the least carbamate formation according to 61 resulted as satisfyingly only under more vigorous
1
400 MHz H NMR spectroscopy in CDCl3.
conditions. Increasing the catalyst loading to
Adding a tiny amount (0.3 mol% relative to dietha- 2.0 mol% (relative to 59), the temperature to reflux,
nolamine) of MoO2Cl2A(DMF)2 to mixtures of phenyl and the reaction time to 4 h were indispensable meas-
(2) or tert-butyl isocyanate (3.3 equivalents) and di- ures for isolating the 3:1 adduct 66 in 97% yield.
CTHUNGTRENNUNG
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
Tricarbamate and tetracarbamate syntheses were Mechanistic Considerations
feasible, too (Scheme 6). We chose 1,1,1-tris(hydroxy-
methyl)ethane (62) and pentaerythritol (63) as a triol The second paragraph of the Results and Discussion
and a tetraol, respectively, and phenyl isocyanate (2) section delineates why we had hoped that MoO2Cl2
as well as tert-butyl isocyanate (21) as their partners. might activate isocyanates such that alcohols are car-
The OH groups of 62 and 63 are neopentylic and bamoylated efficiently. Specifically, we had speculated
hence located in sterically congested environments. that MoO2Cl2 and isocyanates undergo a – possibly 2-
ꢁ
The extent of congestion should worsen when the O
step – [2+2]-cycloaddition, forming the 2-molybda-
H turn into O carbamoyl groups. Surprisingly, what- 1,3-oxazetidin-4-one 91[22] or its DMF-complex. Since
ꢁ
ever such steric effects, our major obstacle for realiz- MoO2Cl2 and MoO2Cl2ACTHNUGRTNEUNG(DMF)2 revealed an extraordi-
ing the intended polyadditions was the liphophobicity nary catalytic efficiency for carbamate formation,
of polyols 62 and 63. It made dropping CH2Cl2 as indeed, this paper ends by interpreting a selection of
a solvent and increasing the temperature mandatory. literature findings on reactions between oxo-com-
Heating a mixture of tris(hydroxymethyl)ethane (62), plexes
3.3 equiv. of phenyl isocyanate (2), and 0.3 mol% (Scheme 7).[30,31,32,33,34] This factual background is in-
(with respect to 62) MoO2Cl2A(DMF)2 in 1,2-dichloro- corporated in the mechanism(s), which we propose
of
molybdenum
and
isocyanates
CTHUNGTRENNUNG
ethane led to a clear solution. Aqueous work-up after for our carbamate syntheses in Scheme 8. We suggest
60 min delivered the analytically pure tricarbamate 64 that the reactions shown in Scheme 7 and the activa-
in quantitative yield.[26] The addition of tris(hydroxy- tion of isocyanates have a commonality according to
methyl)ethane (62) to tert-butyl isocyanate (21) fur- our perception (Scheme 8): they start with a [2+2]-
nished tricarbamate 65 when we used more MoO2Cl2 cycloaddition, which renders molybdaoxazetidinones.
A
Cp2MoO and excess N-phenyl isocyanate (2) pro-
the reaction time (2 h). The addition of pentaerythri- vided the molybdaoxazetidinone[35] 68 in 39% yield
tol (63) to 4.4 equiv. of phenyl isocyanate (2) was real- after 1.5 h according to ref.[36] (Scheme 7, entry 1).
ized in DMF at 608C within 20 min. Employing The reaction temperature was not specified but is un-
0.4 mol% (with respect to the tetraol) MoO2Cl2 likely to have exceeded ~408C because the solvent
ACHTUNGTRENNUNG
(DMF)2 as a catalyst tetracarbamate 66 was isolated was CH2Cl2.[36] Compound 68 was characterized by X-
in a quantitative yield.[26] The 4-fold addition of pen- ray crystallography in the solid state. To the best of
taerythritol (63) to tert-butyl isocyanate (21) was our knowledge 68 constitutes the only precedence for
a challenging task. Chlorinated solvents (CH2Cl2, the formation of an isolable 2-molybda-1,3-oxazeti-
CHCl3, 1,2-dichloroethane) showed low conversions din-4-one from an oxo molybdenum complex at all. It
even after prolonged heating at reflux temperature. must be noted, however, that 68 contains Mo(IV)
In DMF the OH-containing tricarbamate 92[29] whereas the molybdaoxazetidinones 85 and/or 91 (or
formed at 608C within 2 h. This followed from their DMF complexes), which we propose as carba-
a H NMR spectrum (300 MHz, DMSO) of an aliquot moylating entities in the catalytic cycles of Scheme 8
taken from the reaction mixture and freed from the contain Mo(VI). Under the reaction conditions the
solvent. The spectrum showed nothing except the hy- molybdaoxazetidinone[35] 68 did not expel carbon di-
droxytricarbamate and trace amounts of the tetracar- oxide and provide an imido-molybdenum complex 69
bamate. Achieving the fourth carbamoylation was thereby.[36,37]
cumbersome. It required using 8.0 equiv. of isocyanate
MoO2Cl2ACHTUGNTR(EUNNNG MeCN)2 (70), which is an acetonitrile an-
21 and heating the reaction mixture at 608C for 19 h. alogue of our second catalyst MoO2Cl CTHUNGTRENNUNG
2A(DMF)2, and
Taking these provisions we isolated a 64:36 mixture an equimolar amount of N-tert-butyl isocyanate (21)
of tetracarbamate 67 and the OH-containing tricarba- provided a near-perfect yield of an imido-complex
1
mate 92[29] in quantitative yield according to H NMR (Scheme 7, entry 2).[38] By drawing its structure as
analysis (300 MHz, DMSO). At 808C the combined vaguely as 71 the authors left open whether this com-
yield 67+92[29] decreased, which hints at the reversi- plex is an oxo-bridged trimer or maybe a dimer.[38]
bility of the formation of sterically hindered carba- The overall transformation of entry 2 exemplifies
mates from alcohols and isocyanates; the 67:92 ratio a “heterocumulene metathesis”[39] because of the fol-
remained unaffected.
lowing bond interconversion: Mo=Ocomplex +N=
Diols and diisocyanates reacted readily, too, proba- Cisocyanate!Mo=Ncomplex +O=Ccarbon dioxide. The metathe-
bly giving polycarbamates (“polyurethanes”). Howev- sis of entry 2 was conducted at 258C in acetonitrile
er, these were not characterized beyond the fact that while the metatheses of entries 3–7 required tempera-
gels (e.g., from bisphenol A and diisocyanate 36 or tures up to 1408C.[40,41,42,43] The latter engage a selec-
solids (e.g., from cis- oder trans-cyclohexane-1,4-diol tion of molybdenum oxo-complexes (72, 75, 77, 79,
and diisocyanate 36) were obtained.
and 81) and aliphatic as well as aromatic isocyanates.
They delivered molybdenum imido-complexes, like-
wise, namely compounds 74, 76, 78,[44] 80, and 82, re-
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Christian Stock and Reinhard Brꢀckner
FULL PAPERS
Scheme 7.
daoxazetidinone[36] 68 (entry 1). CO2-delivering heterocumulene metatheses of molybdenum(VI) oxo-complexes with isocya-
nates (entries 2–7). These metatheses can be rationalized as domino [2+2]-cycloadditions/[2+2]-cycloreversions (while re-
ACHTUNGTRENNUNG[2+2]-Cycloaddition of molybdenum(IV) oxo-complex Cp2MoO to N-phenyl isocyanate (2) forming the molyb-
AHCTUNGTRENNUNG
membering that none of the molybdaoxazetidinones drawn in brackets was actually observed). The grey shades show the
substructures, which result from the Mo=O moiety of the starting complex and the C=N bond of the isocyanate.
8
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
Scheme 8. Proposed mechanism(s) of the MoO2Cl2-catalyzed addition of alcohols (83) to isocyanates (88). In the “first cycle
mechanism” compound 90 (or its DMF complex) may be considered as the resting state of the catalyst and the molybda-1,3-
oxazetidinone 85 (or its DMF complex) as the active state. The “second cycle mechanism” allows an analogous classification
of compound 86 (or its DMF complex) as the resting state of the catalyst and of the molybda-1,3-oxazetidinone 91 (or its
DMF complex) as the active state.
spectively. Carbon dioxide should have been a stoi- begin with a [2+2]-cycloaddition. In either case it
chiometric side-product in all instances, but its forma- combines the Mo=O bond of a molybdenum(VI) oxo
tion was only proved for entries 4, 5, and 7. Last but complex – namely the dioxo complex 90 (or a species
not least CO2 was released from CpMoOCl2 and containing additionally DMF) or the iminooxocom-
phenyl isocyanate under non-specified conditions.[30] plex 86 (or a species containing additionally DMF) –
This remained an observation, which was neither fol- with the C=N bond of an isocyanate. On the (short-
lowed up nor viewed as the manifestation of a hetero- est) productive pathways the resulting molybda-1,3-
cumulene metathesis.[30]
oxazetidinone 85 and 91, respectively, do not cyclore-
It is an intriguing insight that the molybdaoxazetidi- vert and complete a heterocumulene metathesis
none formation of Scheme 7 (entry 1) and the hetero- thereby. These species rather appear as plausible
cumulene metatheses of Scheme 7 (entries 2–7) can “active states” of the “dormant catalysts” 90 and 86,
be accomodated in a unifying scheme. This becomes respectively. This attribute would be justified if their
possible by interpreting these metatheses as resulting C=O bond picked up the alcohol by forming a tetrahe-
from [2+2]-cycloadditions (akin to entry 1) and ensu- dral intermediate. This step can be likened to the in-
ing [2+2]-cycloreversions. If in such domino process- augural step of an uncatalyzed acylation of a heteroa-
es the cycloreversion was faster than the cycloaddition tom nucleophile by a standard carboxylic or carbonic
the putative cycloadducts would have escaped obser- acid-based acylating agent. If the latter is a 4-mem-
vation at least easily if not necessarily.
bered ring, that is, a b-lactam or b-lactone such an
The evidence of Scheme 7 and the underlying acylation is believed to proceed faster than usually.
mechanistic rationale are the cornerstone of two This might be true for the “4-membered ring carba-
mechanisms, which we propose for the Mo(VI)-cata- mates” 85 and 91, too. If the surmised tetrahedral in-
lyzed carbamate formations of the present study termediates – symbolized by the charge-free formulas
(Scheme 8). The closest analogy to literature findings 87 and 89 – break down by a [2+2]-cycloreversion of
holds for what we call the “first cycle mechanism”. sorts, an N,O-disubstituted iminocarbonic acid results.
The“second cycle mechanism” would be invoked if It tautomerizes to give the carbamate (84). Concomi-
the [2+2]-cycloreversion 85!86+CO2 led out of the tantly, the “dormant catalysts” 90 and 86, respectively,
“first cycle domain”. Both the “first cycle mechanism” are regenerated. They should lead the next substrate
and the “second cycle mechanism” are suggested to molecule into the catalytic cycle.
Adv. Synth. Catal. 0000, 000, 0 – 0
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Conclusions
Chemie and Biochemie, University of Freiburg). IR spectra:
Perkin–Elmer FT-IR Paragon 1000 (film) and Nicolet
Magna IR 760 (ATR). Optical rotations measured with
a Perkin–Elmer polarimeter 341 MC at 589 nm/208C and
In summary, we have introduced MoO2Cl2 and its bis-
DMF complex as highly efficient catalysts for mild
additions of alcohols to isocyanates. Both catalysts are
cheap, odorless, non-toxic, and non-volatile solids. In
calculated according to the Drude equation {[a]D =(aexp
ꢄ
100)/(cꢄd)}; rotational values are the average of five meas-
urements of aexp in a given solution of the corresponding
AHCTUNGTRENNUNG
a typical experiment 100 ppm of MoO2Cl2ACTHNUTRGNE(NUG DMF)2 suf-
sample.
ficed at room temperatuere for catalyzing the addi-
tion of (ꢁ)-menthol (10) to N-phenyl isocyanate (2).
This reaction furnished carbamate 11 in 100% yield
after just 20 min. Even sterically encumbered reac-
tants like tert-butyl alcohol (16) or a,a-dimethylpro-
pargylic alcohol (17) and tert-butyl isocyanate (21)
gave the respective carbamates at room temperature
in high yields and in at most 2 h. Additions of select-
ed monovalent alcohols to industrially used diisocya-
nates in the presence of 0.1–1.0 mol% of the catalyst
gave the corresponding dicarbamates 39–47 in 95–
100% yield again in 2 h or less. A number of diols
and oligools reacted with monoisocyanates to give the
respective di- and oligocarbamates 51–56 and 64–67,
Dimethyl (E,E)-5-(N-Phenylcarbamoyloxy)nona-2,6-
dienoate (6)
MoO2Cl
ground under a nitrogen atmosphere with the stirring bar.
Afterwards, solution of hydroxy ester (124.8 mg,
2ACHTUNGTERN(NUNG DMF)2 (1.9 mg, 5.5 mmol, 1.0 mol%) was finely
a
1
546.8 mmol) in CH2Cl2 (1.8 mL) was added at room tempera-
ture followed by N-phenyl isocyanate (71 mL, 78 mg,
0.66 mmol, 1.2 equiv.). After 60 min the reaction mixture
was diluted with ethyl acetate (16 mL) and aqueous citric
acid solution (10 wt%, 7 mL). The aqueous phase was ex-
tracted with ethyl acetate (3ꢄ12 mL). The combined organic
phases were washed with aqueous citric acid (10 wt%,
12 mL), saturated aqueous NaHCO3-solution (20 mL), and
brine (12 mL). After drying the organic phases over Na2SO4
the solvent was evaporated under reduced pressure. Flash
chromatography (3 cmꢄ23 cm, cyclohexane:ethyl acetate
2:1, 700 mL) furnished the carbamate 6 as a colorless liquid;
respectively, in 94–100% yield. This MoO2Cl2ACTHNUTRGENUG(N DMF)2-
catalyzed carbamate syntheses from polyvalent alco-
hols and polyvalent isocyanates should be applicable
to polymer and dendrimer synthesis. Diethanolamine
(59) added to isocyanates with perfect N-selectivity in
1
yield: 186.1 mg (98%). H NMR (400.13 MHz, CDCl3): d=
2.51 (mc, 4H, 4-H2, 6-H2), 3.71 (s, 6H, 2ꢄOCH3), 5.04 (tt,
the absence of catalyst. Addition of MoO2Cl2ACTHNUTRGENUG(N DMF)2
1H, J5,4-H(1) ꢃJ5,4-H(2) =6.0 Hz, 5-H), 5.89 (ddd, 2H, J2,3
=
allowed three-fold additions to N-phenyl isocyanate
(2) and to N-tert-butyl isocyanate (21); both yields
were 97%.
4
4
15.6 Hz, J2,4-H(1) ꢃ J2,4-H(2) =1.4 Hz, 2-H, 8-H), 6.89 (ddd, 2H,
J
3,2 =15.6 Hz, J3,4-H(1) ꢃJ3,4-(2) =7.3 Hz, 3-H, 7-H), 6.99 (br s,
1H, NH), 7.04 (tt, 1H, Jpara,meta =7.4 Hz, 4Jpara,ortho =1.3 Hz,
Hpara), AA’BBꢅ signal centered at dA =7.28 and dB =
7.37 ppm (4H, A: 2ꢄHmeta
,
B: 2ꢄHortho); 13C NMR
(100.63 MHz, CDCl3): d=36.24 (C-4, C-6), 51.58 (2ꢄ
OCH3), 71.50 (C-5), 118.77 (br s, 2ꢄCortho), 123.60 (Cpara),
124.30 (C-2, C-8), 129.03 (2ꢄCmeta), 137.67 (Cipso), 143.00 (C-
3, C-7), 152.64 (Ccarbamate), 166.44 ppm (C-1, C-9); IR (film):
Experimental Section
General Information
˜
n=3330, 2360, 2340, 1725, 1660, 1600, 1540, 1500, 1445,
All reactions were performed in oven-dried (1108C) glass-
ware under N2. CH2Cl2 was distilled from CaH2. Anhydrous
DMF (AcroSeal) was used as received. Flash chromatogra-
phy[20] [column diameter (cm)ꢄfilling height; kind and
amount of solvent used] was conducted on silica gel (Ma-
cherey–Nagel & Co. silica gel 60, 230–400 mesh, ASTM).
Yields refer to analytically and spectroscopically pure sam-
1315, 1275, 1220, 1175, 1085, 1050, 1030, 975, 900, 850, 770,
695 cmꢁ1; HR-MS (CI, NH3): m/z=365.17110 (ꢁ0.4 ppm),
+
calcd. for C18H25N2O6 (M+NH4 ): 365.17126.
Dimethyl (E,E)-5-[N-(4-
Methoxyphenyl)carbamoyloxy]nona-2,6-dienoate (7)
1
ples. H NMR [CHCl3 (d=7.26 ppm) as internal standard in
CDCl3, acetone-d5 (d=2.05 ppm) as internal standard in
acetone-d6, or DMSO-d5 (d=2.50 ppm) as an internal stan-
dard in DMSO-d6]: Varian Mercury VX 300, Bruker AM
400, and Bruker DRX 500. Integrals in accordance with as-
signments; coupling constants in Hz. 1H NMR hyperfine
structures were interpreted by 1st order analysis with the ex-
ception of AB spectra or AB parts of ABX spectra, ABX2
spectra, etc. 13C NMR [CDCl3 (d=77.10 ppm) as an internal
standard in CDCl3, acetone-d6 (d=29.84 ppm) as internal
standard in acetone-d6, or DMSO-d6 (d=39.52 ppm) as an
internal standard in DMSO-d6]: Bruker AM 400 and Bruker
DRX 500. Assignments of 1H and 13C NMR resonances
refer to IUPAC nomenclature except within substituents
(where primed numbers are used). Combustion analyses: F.
Tçnnies and A. Siegel (at the Institut fꢀr Organische
MoO2Cl
ground under a nitrogen atmosphere with the stirring bar.
Afterwards, solution of hydroxy ester (116.2 mg,
2ACHTUNGTERN(NUNG DMF)2 (1.8 mg, 5.1 mmol, 1.0 mol%) was finely
a
1
509.1 mmol) in CH2Cl2 (1.7 mL) was added at room tempera-
ture followed by N-(4-methoxyphenyl) isocyanate (80 mL,
91 mg, 0.61 mmol, 1.2 equiv.). By and by the reaction solu-
tion turned red. After 190 min the mixture was diluted with
ethyl acetate (12 mL) and aqueous citric acid solution
(10 wt%, 6 mL). The aqueous phase was extracted with
ethyl acetate (3ꢄ12 mL). The combined organic phases
were washed with aqueous citric acid (10 wt%, 10 mL), satu-
rated aqueous NaHCO3-solution (15 mL), and brine
(15 mL). After drying the organic phases over Na2SO4 the
solvent was evaporated under reduced pressure. Flash chro-
matography (3 cmꢄ21 cm, cyclohexane:ethyl acetate 2:1,
10
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
350 mL, 3:2, 500 mL) furnished the carbamate 7 as a color-
less liquid; yield: 187.9 mg (98%). 1H NMR (400.13 MHz,
CDCl3): d=AA’BBꢅ signal centered at d=2.48 (4H, 4-H2,
6-H2), 3.69 (s, 6H, 2ꢄCO2CH3), 3.73 (s, 3H, ArOCH3), 5.00
After 75 min the colorless suspension was diluted with ethyl
acetate (12 mL) and aqueous citric acid solution (10 wt%,
8 mL). The aqueous phase was extracted with ethyl acetate
(3ꢄ12 mL). The combined organic phases were washed with
aqueous citric acid (10 wt%, 16 mL), saturated aqueous
NaHCO3 solution (16 mL), and brine (12 mL). After drying
the organic phases over Na2SO4 the solvent was evaporated
under reduced pressure. Flash chromatography (3 cmꢄ
23 cm, cyclohexane:ethyl acetate 2:1, 750 mL) furnished the
carbamate 9 as a white solid; yield: 180 mg (100%); mp 7–
(tt, 1H, J5,4-H(1) ꢃJ5,4-H(2) =6.0 Hz, 5-H), 5.87 (ddd, 2H, J2,3
=
4
4
15.6 Hz, J2,4-H(1) ꢃ J2,4-H(2) =1.4 Hz, 2-H, 8-H), 6.86 (ddd, 2H,
J
3,2 =15.5, J3,4-H(1) ꢃJ3,4-H(2) =7.4 Hz, 3-H, 7-H), AA’BBꢅ
signal centered at dA =6.83 and dB =7.26 (4H, A: 2ꢄHmeta
,
B: 2ꢄHortho), 6.97 ppm (br s, NH); 13C NMR (100.63 MHz,
CDCl3): d=36.24 (C-4, C-6), 51.50 (2ꢄCO2CH3), 55.38
(ArOCH3), 71.30 (C-5), 114.16 (2ꢄCmeta), 120.62 (br s, 2ꢄ
Cortho), 124.16 (C-2, C-8), 130.72 (Cipso), 143.08 (C-3, C-7),
153.00 (Ccarbamate), 155.97 (Cpara), 166.39 ppm (C-1, C-9); IR
1
888C. H NMR (400.13 MHz, CDCl3): d=2.50 (mc, 4H, 4-
H2, 6-H2), 3.70 (s, 6H, 2ꢄOMe), 5.02 (tt, 1H, J5,4-H(1)
ꢃ
4
J
5,4-H(2) =6.0 Hz, 5-H), 5.88 (ddd, 2H, J2,3 =15.7 Hz, J2,4-H(1)
ꢃ
(film): n=3330, 2950, 2360, 2340, 1725, 1660, 1600, 1535,
4J2,4-H(2) =1.4 Hz, 2-H, 8-H), 6.87 (ddd, 2H, J3,2 =15.6 Hz,
J3,4-H(1) ꢃJ3,4-H(2) =7.4 Hz, 3-H, 7-H), 7.00 (br s, 1 H. NH),
AA’BBꢅ signal centered at dA =7.26 and dB =7.38 ppm (4H,
A: 2ꢄHmeta, B: 2ꢄHortho); 13C NMR (100.63 MHz, CDCl3):
d=36.24 (C-4, C-6), 51.64 (2 ꢄ OCH3), 71.80 (C-5), 116.16
(Cpara), 120.32 (br s, 2 ꢄ Cortho), 124.41 (C-2, C-8), 131.99 (2 ꢄ
Cmeta), 136.83 (Cipso), 142.84 (C-3, C-7), 152.48 (Ccarbamate),
˜
1515, 1440, 1415, 1325, 1275, 1220, 1175, 1110, 1035, 975,
830, 770 cmꢁ1
(ꢁ1.3 ppm), calcd. for C19H27N2O7 (M+NH4 ): 395.18183.
;
HR-MS (CI, NH3): m/z=395.18130
+
Dimethyl (E,E)-5-[N-(4-
Acetylphenyl)carbamoyloxy]nona-2,6-dienoate (8)
˜
166.43 ppm (C-1, C-9); IR (film): n=3310, 2950, 2360, 1725,
1660, 1595, 1535, 1435, 1410, 1360, 1320, 1275, 1220, 1180,
MoO2Cl
ground under a nitrogen atmosphere with the stirring bar.
Afterwards, solution of hydroxy ester (115.5 mg,
2ACHTUNGTRENNUNG(DMF)2 (1.8 mg, 5.1 mmol, 1.0 mol%) was finely
1045, 975, 840, 765 cmꢁ1
: HR-MS (CI, NH3): m/z=
+
443.08250 (+1.6 ppm), calcd. for C18H24N2O6Br (M+NH4 ):
a
1
443.08177.
506.0 mmol) in CH2Cl2 (0.8 mL) was added at room tempera-
ture followed by a suspension of N-(4-acetylphenyl) isocya-
nate (97.8 mg, 607 mmol, 1.2 equiv.) in CH2Cl2 (2.6 mL).
After 90 min the orange-colored mixture was diluted with
ethyl acetate (12 mL) and aqueous citric acid solution
(10 wt%, 8 mL). The aqueous phase was extracted with
ethyl acetate (3ꢄ12 mL). The combined organic phases
were washed with aqueous citric acid (10 wt%, 15 mL), satu-
rated aqueous NaHCO3 solution (20 mL), and brine
(12 mL). After drying the organic phases over Na2SO4 the
solvent was evaporated under reduced pressure. Flash chro-
matography (3 cmꢄ23 cm, cyclohexane:ethyl acetate 3:2,
1000 mL) furnished the carbamate 8 as a yellow oil; yield:
198 mg (100%). 1H NMR (400.13 MHz, CDCl3): d=2.43–
2.50 (m, 4H, 4-H2, 6-H2), partially superimposed by 2.49 (s,
O-(1R,2S,5R)-5-Methyl-2-isopropylcyclohexyl N-
Phenyl Carbamate (11)[45]
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (0.7 mg, 2 mmol, 0.01 mol%) was placed in
a 50-mL flask equipped with a magnetic stirring bar. The
flask was sealed with a rubber serum cap and purged with
dry nitrogen. Afterwards, the crystals were finely ground
with the stirring bar. Subsequently, (ꢁ)-menthol (10, 3.13 g,
20.0 mmol) and CH2Cl2 (20 mL) were added. To this mix-
ture was added in one portion at room temperature N-
phenyl isocyanate (2, 2.61 mL, 2.86 g, 24.0 mmol, 1.2 equiv.).
Instaneously a slightly yellowish solution formed. After
20 min the reaction was quenched by the addition of H2O
(30 mL) and CH2Cl2 (40 mL). The aqueous phase was ex-
tracted with CH2Cl2 (2ꢄ40 mL). The combined organic
phases were dried over Na2SO4. Removal of the solvent
gave the analytically pure carbamate 11 as a white solid;
3H, 2’-H3), 3.64 (s, 6H, 2ꢄOMe), 5.00 (quint, 1H, J5,4
=
4
6.0 Hz, 5-H), 5.83 (dt, 2H, J2,3 =15.6 Hz, J2,4 =1.3 Hz, 2-H,
8-H), 6.82 (dt, 2H, J3,2 =15.5 Hz, J3,4 =7.5 Hz, 3-H, 7-H),
AA’BBꢅ signal centered at dA =7.48 and dB =7.84 (4H, A:
2ꢄHortho, B: 2ꢄHmeta), 7.93 ppm (br s, 1H, NH). 13C NMR
(100.63 MHz, CDCl3): d=26.21 (C-2’), 36.12 (C-4, C-6),
51.45 (2ꢄOCH3), 71.75 (C-5), 117.71 (2ꢄCortho), 124.22 (C-2,
C-8), 129.67 (2ꢄCmeta), 131.96 (Cpara), 142.58 (Cipso), 142.75
(C-3, C-7), 152.35 (Ccarbamate), 166.28 (C-1, C-9), 197.00 ppm
yield: 5.52 g (100%); [a]2D0: ꢁ83.98 (c 0.84, CHCl3); mp
1
988C. H NMR (400.13 MHz, CDCl3): d=0.82 (d, 3H, J2’,1’
=
7.0 Hz, 2’-H3), 0.92 (d, 6H, J1’-CH3,1 ꢃJ5ꢁCH3,5 =6.5 Hz, 1’-CH3
and 5-CH3), 0.85–1.17 (m, 3H, 4-H1, 6-H1, 3-H1), 1.38 (dddd,
1H, J2,1 ꢃJ2,3(1) =11.1 Hz, J2,1ꢅ ꢃJ2,3(2) =3.0 Hz, 2-H), 1.44–1.59
(m, 1H, 5-H), 1.64–1.75 (m, 2H, 3-H2, 4-H2), 1.97 [qqd, 1H,
˜
(C-1’); IR (film): n=3310, 2950, 2360, 1725, 1660, 1595,
1535, 1435, 1410, 1360, 1320, 1275, 1220, 1180, 1045, 975,
840, 765 cmꢁ1. MS (APCI): m/z (%)=390 (M+H+, 100),
238 (6), 211 (76), 107 (8).
J1’,2ꢅ ꢃJ1’,1’-CH3 =7.0 Hz,
J1’,2 =2.6 Hz, CHACTHNUGTNRUEGN(CH3)2], 2.07–2.16
(m, 1H, 6-H2), 4.67 (ddd, 1H, J1,2 ꢃJ1,6-H(1) ꢃ10.9 Hz,
J
J
1,6-H(2) =4.4 Hz, 1-H), 6.55 (br s, 1H, NH), 7.05 (tt, 1H,
para,meta =7.3 Hz, 4Jpara,ortho =1.1 Hz, Hpara), AA’BBꢅ signal
centered at dA =7.30 and dA =7.39 ppm (4H, A: 2ꢄHmeta, B:
2ꢄHortho); 13C NMR (100.63 MHz, CDCl3): d=16.53 (C-2’),
20.90 and 22.12 (C-5, 1’-CH3), 23.59 (C-3), 26.36 (C-1’),
31.47 (C-5), 34.34 (C-4), 41.44 (C-6), 47.41 (C-2), 75.18 (C-
1), 118.61 (2 ꢄ Cortho), 123.23 (Cpara), 129.08 (2ꢄCmeta), 138.31
Dimethyl (E,E)-5-[N-(4-
Bromophenyl)carbamoyloxy]nona-2,6-dienoate (9)
MoO2Cl
ground under a nitrogen atmosphere with the stirring bar.
Afterwards, solution of hydroxy ester (96.5 mg,
2ACHTUNGTRENNUNG(DMF)2 (1.4 mg, 4.2 mmol, 1.0 mol%) was finely
(Cipso), 153.51 ppm (C=O); IR (ATR): n=3350, 2955, 2925,
˜
a
1
423 mmol) in CH2Cl2 (0.8 mL) was added at room tempera-
ture followed by a suspension of N-(4-bromophenyl) isocya-
nate (101 mg, 508 mmol, 1.2 equiv.) in CH2Cl2 (2.0 mL).
2870, 1695, 1600, 1525, 1440, 1390, 1370, 1315, 1300, 1225,
1180, 1085, 1060, 1050, 1030, 985, 970, 925, 900, 880, 865,
835, 765, 755, 735, 690, 630, 530, 505, 475 cmꢁ1; anal. calcd.
Adv. Synth. Catal. 0000, 000, 0 – 0
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Christian Stock and Reinhard Brꢀckner
FULL PAPERS
for C17H25NO2 (275.4): C 74.14, H 9.15, N 5.09; found: C
73.95, H 9.39, N 4.99.
1600, 1540, 1500, 1445, 1370, 1315, 1215, 1080, 1065, 1030,
955, 855, 745, 675, 630, 535, 500 cmꢁ1; anal. calcd. for
C10H9NO2 (175.2): C 68.56, H 5.18, N 8.00; found: C 68.84,
H 5.21, N 8.31.
O-Benzyl N-Phenyl Carbamate (22)[46]
O-Cyclohexyl N-Phenyl Carbamate (25)[49]
This white solid (yield: 812 mg, 102%) was prepared from
benzylic alcohol (12, 0.36 mL, 0.38 g, 3.5 mmol) and N-
phenyl isocyanate (2, 0.46 mL, 0.50 g, 4.2 mmol, 1.2 equiv.)
This white solid (yield: 1.81 g, 95%) was prepared from cy-
clohexanol (15, 0.91 mL, 0.87 g, 8.7 mmol) and N-phenyl iso-
cyanate (2, 1.13 mL, 1.24 g, 10.4 mmol, 1.2 equiv.) in the
in the presence of MoO2Cl2ACHTNUTRGENNUG(DMF)2 (1.2 mg, 3.5 mmol, 0.10
mol%) as described for 11. mp 71–738C. 1H NMR
(400.13 MHz, CDCl3): d=5.21 (s, 2H, H2benzyl), 6.69 (br s,
1H, NH), 7.07 (tt, 1H, Jpara,meta =7.3 Hz, 4Jpara,ortho =1.2 Hz,
Hpara), 7.28–7.43 ppm (m, 9H, 9ꢄHAr); 13C NMR
(100.63 MHz, CDCl3): d=66.97 (Cbenzyl), 118.86 (2ꢄCortho),
123.49 (Cpara), 128.27 and 128.59 and 129.02 (2ꢄCmeta, 2ꢄ
presence of MoO2Cl2ACHTNUGRTNE(NUG DMF)2 (1.2 mg, 3.5 mmol, 0.10 mol%)
as described for 11; mp 78–798C. 1H NMR (400.13 MHz,
CDCl3): d=1.21–1.33 (m, 1H), 1.34–1.52 (m, 4H), 1.52–1.61
(m, 1H), 1.70–1.79 (m, 2H, 2-H1, 6-H1), 1.90–1.98 (m, 2H,
2-H2, 6-H2), 4.77 (tt, 1H, J1,2(1) =9.0 Hz, J1,2(2) =3.9 Hz, 1-H),
4
C
ortho’’, 2ꢄCmeta)a, 128.31 (Cpara’), 136.12 (Cipso’), 137.88 (Cipso),
6.64 (br s, 1H, NH), 7.05 (tt, 1H,Jpara,meta =7.3 Hz, Jpara,ortho
=
1.2 Hz, Hpara), AA’BBꢅ signal centered at dA =7.29 and dB =
˜
153.58 ppm (C=O); IR (ATR): n=3270, 3135, 3075, 2975,
1690, 1600, 1530, 1500, 1445, 1315, 1215, 1085, 1055, 1025,
975, 920, 900, 845, 755, 735, 690, 575, 500 cmꢁ1; anal. calcd.
for C14H13NO2 (227.3): C 73.99, H 5.77, N 6.14; found: C
73.79, H 5.88, N 6.16.
7.39 ppm (4H, A: 2ꢄHmeta B: 2ꢄHortho); 13C NMR
,
(100.63 MHz, CDCl3): d=23.71 (C-4), 25.35 (C-3, C-5),
31.87 (C-2, C-6), 73.50 (C-1), 118.68 (2ꢄCortho), 123.08
(Cpara), 128.89 (2ꢄCmeta), 138.26 (Cipso), 153.42 ppm (C=O);
˜
IR (ATR): n=3350, 3135, 3060, 2930, 2860, 1735, 1705,
O-Geranyl N-Phenyl Carbamate (23)[47]
1655, 1600, 1525, 1500, 1445, 1385, 1315, 1215, 1080, 1055,
1030, 920, 900, 855, 840, 755, 735, 690, 595, 505, 440 cmꢁ1
;
This colorless oil (yield: 1.16 g, 103%) was prepared from
geraniol (13, 0.72 mL, 0.63 g, 4.1 mmol) and N-phenyl isocy-
anate (2, 0.54 mL, 0.59 g, 4.9 mmol, 1.2 equiv.) in the pres-
anal. calcd. for C13H17NO2 (219.3): C 71.21, H 7.81, N 6.39;
found: C 71.10, H 7.96, N 6.36.
O-tert-Butyl N-Phenyl Carbamate (26)[50]
ence of MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (1.4 mg, 4.1 mmol, 0.10 mol%) as
1
described for 11. H NMR (400.13 MHz, CDCl3): d=1.62 (d,
Z
3H,4J7-CH3(Z),6 =0.7 Hz, 7-CH34 ), 1.70 (d, 3H,4J7-CH3(E),6
=
This white solid (yield: 625 mg, 98%) was prepared from
tert-butyl alcohol (16, 0.314 mL, 245 mg, 3.30 mmol) and N-
phenyl isocyanate (2, 0.43 mL, 0.47 g, 4.0 mmol, 1.2 equiv.)
E
1.1 Hz, 7-CH3 ), 1.75 (d, 3H, J3-CH3,2 =1.3 Hz, 3-CH3), 2.04–
2.17 (m, 4H, 4-H2 and 5-H2), 4.71 (d, 2H, J1,2 =7.1 Hz, 1-
4
4J6,7-CH3(Z)
in the presence of MoO2Cl2ACHTNUTRGENNUG(DMF)2 (11.4 mg, 33.0 mmol, 1.0
H2), 5.11 (tqq, 1H, J6,5 =6.8 Hz, J6,7-CH3(E)
ꢃ
mol%) as described for 11; mp 238C. 1H NMR
(400.13 MHz, CDCl3): d=1.49 (s, 9H, t-Bu), 6.62 (br s, 1H,
4
ꢃ1.4 Hz, 6-H), 5.41 (tq, 1H, J2,1 =7.1 Hz, J2,3-CH3 =1.3 Hz, 2-
H), 6.78 (br s, 1H, NH), 7.05 (tt, 1H, Jpara,meta =7.3 Hz,
4Jpara,ortho =1.2 Hz, Hpara), AA’BBꢅ signal centered at dA =
7.29 and dB =7.39 ppm (4H, A: 2ꢄHmeta, B: 2ꢄHortho);
13C NMR (100.63 MHz, CDCl3): d=16.64 (C-3), 17.82 (7-
CH3 ), 25.80 (7-CH3 ), 26.44 (C-5), 39.68 (C-4), 118.53 (C-
2), 118.77 (2ꢄCortho), 123.46 (Cpara), 123.86 (C-6), 129.15 (2 ꢄ
Cmeta), 131.99 (C-7), 138.13 (Cipso), 142.68 (C-3), 153.76 ppm
4
NH), 6.99 (tt, 1H, Jpara,meta =7.2 Hz, Jpara,ortho =1.4 Hz, Hpara),
AA’BBꢅ signal centered at dA =7.24 and dB =7.33 ppm (4H,
A=2ꢄHmeta, B=2ꢄHortho); 13C NMR (100.63 MHz, CDCl3):
d=28.42 [C
123.06 (Cpara), 129.00 (2ꢄCmeta), 138.47 (Cipso), 152.94 ppm
(CH3)3], 118.68 (2ꢄCortho),
ACHTUGTNRNENUG(CH3)3], 80.50 [CACHUTNGTRENNUGN
Z
E
˜
(C=O); IR (ATR): n=3295, 2985, 1685, 1600, 1525, 1505,
1490, 1480, 1440, 1390, 1365, 1315, 1300, 1240, 1145, 1085,
1055, 1020, 910, 895, 825, 775, 745, 695, 620, 595, 510, 460,
420 cmꢁ1; anal. calcd. for C11H15NO2 (193.2): C 68.37, H
7.82, N 7.25; found: C 68.36, H 8.02, N 7.26.
˜
(C=O); IR (film): n=3325, 3200, 3135, 3060, 3025, 2970,
2925, 2855, 1935, 1845, 1735, 1710, 1600, 1540, 1500, 1445,
1375, 1315, 1275, 1225, 1180, 1155, 1100, 1085, 1055, 1030,
995, 935, 900, 850, 830, 770, 755, 720, 690, 510 cmꢁ1; anal.
calcd. for C17H23NO2 (273.4): C 74.69, H 8.48, N 5.12; found:
C 74.43, H 8.55, N 5.36.
O-a,a-Dimethylpropargyl N-Phenyl Carbamate
(27)[51]
O-Propargyl N-Phenyl Carbamate (24)[48]
This white solid (yield: 1.12 mg, 102%) was prepared from
2-methyl-3-butyn-2-ol (17, 0.53 mL, 0.46 g, 5.4 mmol) and N-
phenyl isocyanate (2, 0.71 mL, 0.78 g, 6.5 mmol, 1.2 equiv.)
This brown solid (yield: 1.92 g, 100%) was prepared from
propargylic alcohol (14, 0.65 mL, 0.62 g, 11 mmol) and N-
phenyl isocyanate (2, 1.44 mL, 1.57 g, 13.2 mmol, 1.2 equiv.)
in CH2Cl2 (1.1 mL) in the presence of MoO2Cl2ACHTUNGTRENNUNG(DMF)2
in the presence of MoO2Cl
(DMF)2 (3.9 mg, 11 mmol, 0.10
(18.7 mg, 54.2 mmol, 1.0 mol%) as described for 11; mp
948C. 1H NMR (400.13 MHz, CDCl3): d=1.71 [s, 6H, 1-
(CH3)2], 2.54 (s, 1H, 3-H), 6.75 (br s, 1H, NH), 7.00 (tt, 1H,
mol%) as described for 11; mp 46–498C. 1H NMR
(400.13 MHz, CDCl3): d=2.51 (t, 1H,4J3,1 =2.5 Hz, 3-H),
4.79 (d, 2H,4J1,3 =2.4 Hz, 1-H2), 6.77 (br s, 1H, NH), 7.09 (tt,
J
para,meta =7.3 Hz, 4Jpara,ortho =1.2 Hz, Hpara), AA’BBꢅ signal
1H,
J
para,meta =7.3 Hz, 4Jpara,ortho =1.3 Hz, Hpara), AA’BBꢅ
centered at dA =7.24 and dB =7.37 ppm (4H, A: 2ꢄHmeta, B:
2ꢄHortho); 13C NMR (100.63 MHz, CDCl3): d=29.22 [1-
(CH3)2], 72.20 (C-1), 72.51 (C-3), 84.94 (C-2), 118.74 (2 ꢄ
Cortho), 123.35 (Cpara), 128.96 (2 ꢄ Cmeta), 137.90 (Cipso),
signal centered at dA =7.32 and dB =7.39 ppm (4H, A: 2ꢄ
Hmeta, B: 2ꢄHortho); 13C NMR (100.63 MHz, CDCl3): d=
52.77 (C-1), 75.14 (C-3), 77.97 (C-2), 118.99 (2ꢄCortho),
123.79 (Cpara), 129.06 (2ꢄCmeta), 137.52 (Cipso), 152.75 ppm
˜
151.80 ppm (C=O); IR (ATR): n=3300, 1700, 1600, 1525,
˜
(C=O); IR (ATR): n=3330, 3295, 3140, 3065, 2965, 1705,
1500, 1490, 1470, 1440, 1395, 1380, 1365, 1310, 1300, 1235,
12
asc.wiley-vch.de
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
1190, 1155, 1125, 1080, 1045, 1025, 1000, 950, 915, 895, 830,
770, 745, 690, 665, 625, 545, 535, 510, 420 cmꢁ1; anal. calcd.
for C12H13NO2 (203.1): C 70.92, H 6.45, N 6.89; found: C
70.90, H 6.60, N 7.15.
O-(1R,2S,5R)-5-Methyl-2-isopropylcyclohexyl N-
Butyl Carbamate (30)[45]
This white solid (yield: 1.88 g, 98%) was prepared from (ꢁ)-
menthol (10, 1.17 g, 7.50 mmol) and N-butyl isocyanate (18,
0.92 mL, 0.82 g, 8.3 mmol, 1.1 equiv.) in the presence of
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (2.6 mg, 7.5 mmol, 0.10 mol%) as described
for 11; [a]20: ꢁ668 (c 0.91, CHCl3); mp 498C. 1H NMR
(400.13 MHDz, CDCl3): d=0.74 (d, J2’’,1’’ =7.0 Hz, 3H, 2’’-H3),
0.77–0.92 (m, 2H), 0.83 (d, 3H, J1’’-CH3,1’’ =7.1 Hz, 1’’-CH3),
O-(1R,2S,5R)-5-Methyl-2-isopropylcyclohexyl N-(4-
Methoxyphenyl) Carbamate (28)
This white solid (yield: 625 mg, 98%) was prepared from
(ꢁ)-menthol (10, 859 mg, 5.50 mmol) and N-(4-methoxy-
phenyl) isocyanate (3, 0.78 mL, 0.90 g, 6.0 mmol, 1.1 equiv.)
0.84 (d, 3H, J5’-CH3,5ꢅ ꢃ6.5 Hz, 5’-CH3), 0.87 (t, 3H, J4,3
=
ꢃ
7.4 Hz, 4-H3), 1.01 [dddd, 1H, 2J3’(ax),3’(eq) ꢃJ3’(ax),2ꢅ
J
3’(ax),4’(ax) =12.9 Hz, J3’(ax),4’(eq) =3.4 Hz, 3’-Heq], 1.21–1.34 (m,
in the presence of MoO2Cl2ACHTNUTRGENNUG(DMF)2 (1.9 mg, 5.5 mmol, 0.10
3H), 1.38–1.48 (m, 3H), 1.56–1.66 (m, 2H), 1.81–1.94 [qqd,
1H, J1’’,2’ꢅ ꢃJ1’’,1’’-CH3 =7.0 Hz, JCH(CH3)2,2’ =2.5 Hz, 1’’-H], 1.99
(br d, 1H, J=11.9 Hz, signal contains further, not resolved
couplings, 2’-H), 3.04–3.17 (m, 2H, 1-H2), 4.49 (ddd, 1H,
J1’,2ꢅ ꢃJ1’,6’-H(ax) =10.8 Hz, J1’,6’-H(eq) =4.1 Hz, 1’-H), 4.66 ppm
(br s, 1H, NH); 13C NMR (100.63 MHz, CDCl3): d=13.77
(C-4), 16.53 (C-2’’), 19.93 (C-3), 20.83 and 22.09 (C-5’, 1’-
CH3), 23.64 (C-3’), 26.34 (C-1’’), 31.41 (C-5), 32.20 (C-2),
34.41 (C-4’), 40.68 (C-1), 41.60 (C-6’), 47.52 (C-2’), 74.26 (C-
mol%) as described for 11; [a]2D0: ꢁ66.58 (c 1.17, CHCl3); mp
1058C. 1H NMR (400.13 MHz, CDCl3): d=0.82 (d, 3H,
J
2’,1’ =6.9 Hz, 2’-H3), 0.92 (d, 6H, J1’,1’-CH3 ꢃJ5,5-CH3 =6.5 Hz,
1’-CH3, 5-CH3), 0.84–1.17 (m, 3H, 4-H1, 6-H1, 3-H1), 1.36
(mc, 1H, 2-H), 1.45–1.59 (m, 1H, 5-H), 1.64–1.74 (m, 2H, 3-
H2, 4-H2), 1.97 (sept d, 1H, J1’,2ꢅ ꢃJ1’,1’-CH3 =7.1 Hz, J1’,2
=
2.7 Hz, 1’-H), 2.06–2.16 (m, 1H, 6-H2), 3.78 (s, 3H, OCH3),
4.65 (ddd, 1H, J1,2 ꢃJ1,6-H(ax) ꢃ10.8 Hz, J1,6-H(eq) =4.4 Hz, 1-H),
6.39 (br s, 1H, NH), AA’BBꢅ signal centered at dA =6.84
and dB =7.29 ppm (4H, A: 2ꢄHmeta, B: 2ꢄHortho); 13C NMR
(100.63 MHz, CDCl3): d=16.51 (C-2’), 20.87 and 22.09 (1’-
CH3, 5-CH3), 23.57 (C-3), 26.33 (C-1’), 31.45 (C-5), 34.33 (C-
4), 41.46 (C-6), 47.41 (C-2), 55.55 (OCH3), 75.01 (C-1),
114.29 (2ꢄCmeta), 120.48 (2ꢄCortho), 131.39 (Cipso), 153.78 (C=
˜
1’), 156.57 ppm (C=O); IR (film): n=3370, 2955, 2940, 2870,
2360, 1685, 1655, 1530, 1450, 1390, 1370, 1275, 1240, 1220,
1180, 1140, 1080, 1025, 1000, 985, 965, 920, 845, 770,
625 cmꢁ1; anal. calcd. for C15H29NO2 (255.4): C 70.54, H
11.44, N 5.48; found: C 70.53, H 11.53, N 5.24.
O), 155.83 ppm (Cpara); IR (ATR): n=3320, 2955, 2920,
˜
O-(1R,2S,5R)-5-Methyl-2-isopropylcyclohexyl N-
2865, 2845, 1690, 1600, 1530, 1455, 1415, 1315, 1235, 1180,
1050, 1030, 985, 970, 925, 825, 780, 770, 730, 660, 590, 530,
520, 505, 470 cmꢁ1; calcd. for C18H27NO3 (305.4): C 70.79, H
8.91, N 4.59; found: C 70.52, H 8.70, N 4.77.
Benzyl Carbamate (31)[52]
This white solid (yield: 1.13 g, 103%) was prepared from
(ꢁ)-menthol (10, 594 mg, 3.80 mmol) and N-benzyl isocya-
nate (19, 0.52 mL, 0.56 g, 4.2 mmol, 1.1 equiv.) in the pres-
ence of MoO2Cl2ACTHNUGTRNEUNG(DMF)2 (1.3 mg, 3.8 mmol, 0.10 mol%) as
described for 11; [a]2D0: ꢁ52.68 (c 0.92, CHCl3); mp 928C.
O-(1R,2S,5R)-5-Methyl-2-isopropylcyclohexyl N-(4-
Acetylphenyl) Carbamate (29)
1H NMR (400.13 MHz, CDCl3): d=0.80 (d, 3H, J2’,1’
7.1 Hz, 2’-H3), 0.85–1.14 (m, 2H), 0.91 [d, 6H, J1’-CH3,1ꢅ
=
ꢃ
This orange solid (yield: 748 mg, 102%) was prepared from
(ꢁ)-menthol (10, 359 mg, 2.30 mmol) and N-(4-acetylphen-
yl) isocyanate (4, 408 mg, 2.53 mmol, 1.1 equiv) in the pres-
J
5-CH3,5 =5.5 Hz, 1’-CH3, 5-CH3], 1.31 (dddd, 1H, J ꢃ J=
11.6 Hz, JꢃJ=3.0 Hz), 1.40–1.56 (m, 1H), 1.40–1.56 (m,
1H), 1.61–1.72 (m, 2H), 1.84–1.99 (br m, 1H), 2.03–2.12 (m,
1H), not resolved AB signal (br d, dA ꢃ dB =4.37, 2H, 2ꢄ
ence of MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (0.8 mg, 2 mmol, 0.10 mol%) as de-
scribed for 11; [a]2D0: ꢁ77.88 (c 0.26, CHCl3); mp 1188C.
HBn), 4.60 [ddd, 1H, J1’,2ꢅ ꢃJ1’,6’ꢁH(ax) =10.8 Hz, J1’,6’ꢁH(ꢀq)
=
1H NMR (400.13 MHz, acetone): d=0.81 (d, 3H, J2’,1’
=
4.4 Hz, 1-H], 4.89 (br s, 1H, NH), 7.23–7.37 ppm (m, 5H,
5ꢄHAr); 13C NMR (100.63 MHz, CDCl3): d=16.58 (C-2’),
20.87 and 22.12 (C-5, 1’-CH3), 23.64 (C-3), 26.37 (C-1’),
31.44 (C-5), 34.38 (C-4), 41.56 (C-6), 45.06 (Cbenzyl), 47.50
(C-2), 74.81 (C-1), 127.40 and 127.48 (Cpara, 2ꢄCortho), 128.66
7.0 Hz, 2’-H3), 0.90 (d, 3H, J1-CH3,1’ =7.1 Hz, 1’-CH3), 0.91 (d,
3H, J5-CH3,5 =6.7 Hz, 5-CH3), 0.84–0.93 (m, 1H, 4-H1), 0.95–
1.16 (m, 2H, 6-H1, 3-H1), 1.37 (dddd, 1H, J2,1 ꢃJ2,3(1)
=
11.5 Hz, J2,1ꢅ ꢃJ2,3(2) =3.0 Hz, 2-H), 1.50 (mc, 1H, 5-H), 1.64–
1.72 (m, 2H, 3-H2, 4-H2), 1.97 (qqd, 1H, J1’,2ꢅ ꢃJ1’,1’-CH3
ꢃ7.0 Hz, J1’,2 =2.6 Hz, 1’-H), 2.03–2.09 (m, 1H, 6-H2), 2.53
[s, 3H, C(=O)CH3], 4.66 (ddd, 1H, J1,2 ꢃJ1,6(1) ꢃ10.9 Hz,
(2ꢄCmeta), 138.93 (Cipso), 156.61 ppm (C=O); IR (ATR): n=
˜
3335, 2955, 2920, 2870, 1680, 1515, 1455, 1370, 1245, 1180,
1120, 1040, 985, 970, 910, 780, 750, 695, 630, 580, 515,
480 cmꢁ1; anal. calcd. for C18H27NO2 (289.4): C 74.70, H
9.40, N 4.84; found: C 74.83, H 9.39, N 4.75.
J
1,6(2) =4.4 Hz, 1-H), 6.89 (br s, 1H, NH), AA’BBꢅ signal cen-
tered at dA =7.73 and dB =7.95 ppm (4H, A: 2ꢄHortho, B:
2ꢄHmeta); 13C NMR (100.63 MHz, acetone): d=16.64 (C-2’),
20.97 (1’-CH3), 22.29 (5-CH3), 24.09 (C-3), 26.34 [(C(=
O)CH3], 26.87 (C-1’), 32.07 (C-5), 34.88 (C-4), 41.99 (C-6),
48.07 (C-2), 75.24 (C-1), 118.06 (2ꢄCortho), 130.29 (2ꢄCmeta),
132.44 (Cpara), 144.64 (Cipso), 153.88 ppm [NC(=O)O], 196.47
O-(1R,2S,5R)-5-Methyl-2-isopropylcyclohexyl N-
Cyclohexyl Carbamate (32)[45]
This white solid (yield: 2.78 g, 90%) was prepared from (ꢁ)-
menthol (10, 1.72 g, 11.0 mmol) and N-cyclohexyl isocyanate
(20, 1.54 mL, 1.51 g, 12.1 mmol, 1.1 equiv.) in the presence
˜
[(C(=O)CH3]; IR (ATR): n=3300, 2960, 2935, 2860, 1725,
1665, 1585, 1525, 1410, 1360, 1315, 1270, 1215, 1180, 1080,
1040, 970, 960, 820, 765, 700, 545, 500, 475 cmꢁ1; anal. calcd.
for C19H27NO3 (317.4): C 71.89, H 8.57, N 4.41; found C
71.59, H 8.49, N 4.44.
of MoO2Cl2ACHTUNRGTNEUNG(DMF)2 (3.7 mg, 11 mmol, 0.10 mol%) as de-
scribed for 11; [a]2D0: ꢁ59.38 (c 0.92, CHCl3); mp 121–1238C.
1H NMR (400.13 MHz, CDCl3): d=0.79 (d, 3H, J2’’,1’’
=
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
13
ÞÞ
These are not the final page numbers!

Christian Stock and Reinhard Brꢀckner
FULL PAPERS
6.9 Hz, 2’’-H3), 0.72–0.83 (m, 1H), 0.89 (d, 6H,J1’’-CH3,2’ꢅ
ꢃ
O,O’-Diethyl 4-Methyl-1,3-phenylenedicarbamate
(39)[53]
J
5’-CH3,5’ =6.4 Hz, 1’’-CH3, 5’-CH3), 0.90–1.00 (m, 1H), 1.02–
1.23 (m, 4H), 1.24–1.42 (m, 3H), 1.43–1.53 (m, 1H), 1.54–
1.74 (m, 5H), 1.83–1.97 (m, 3H), 2.03 (d, J=11.0 Hz, signal
contains further, not resolved couplings, 1H), 3.44 (br s, 1H,
1-H), 4.43 (br s, 1H, NH), 4.54 ppm [1H,ddd, J1’,2 ꢃJ1’,6’-H(ax)
ꢃ10.3 Hz, J1’,6’-H(eq) =4.3 Hz, 1’-H); 13C NMR (100.63 MHz,
CDCl3): d=16.56 (C-2’’), 20.88 and 22.12 (1’’-CH3, 5’-CH3),
23.66 (C-3’), 24.90 (C-6), 25.62 (C-3, C-5), 26.38 (C-1’’),
31.44 (C-5’), 33.56 (C-2, C-6), 34.43 (C-4’), 41.63 (C-6’),
47.58 (C-2’), 49.78 (C-1), 74.15 (C-1’), 155.75 ppm (C=O);
MoO2Cl
finely ground under
(DMF)2 (2.1 mg, 6.1 mmol, 0.1 mol% rel. to 35) was
nitrogen atmosphere. CH2Cl2
a
(6.1 mL) and ethanol (35, 0.36 mL, 0.28 g, 6.1 mmol) were
added, followed at room temperatuzre by 2,4-toluene diiso-
cyanate (36, 0.35 mL, 0.43 g, 2.4 mmol, 0.4 equiv.). After 1 h
the reaction was quenched by the addition of ethyl acetate
(60 mL) and aqueous citric acid (10 wt%, 24 mL). The aque-
ous phase was extracted with ethyl acetate (2ꢄ50 mL). The
combined organic phases were washed with aqueous citric
acid (10 wt%, 30 mL), saturated aqueous NaHCO3-solution
(20 mL), and brine (20 mL). Drying over Na2SO4 and re-
moval of the solvent gave the dicarbamate 39 as a white
solid; yield: 648 mg (100%); mp 122–1238C. 1H NMR
(400.13 MHz, DMSO): d=1.22 (t, 6H, J2’,1’ =J2’’,1’’ =7.1 Hz,
2’-H3, 2’’-H3), 2.10 (s, 6H, 4-CH3), 4.08 (q, 2H, J1’,2’ =1’-H2)a,
partially superimposed by 4.09 (q, 2H, J1’’,2’’ =7.1 Hz, 1’’-
˜
IR (ATR): n=3350, 2925, 2865, 1675, 1600, 1520, 1445,
1375, 1315, 1275, 1255, 1230, 1180, 1080, 1060, 1040, 985,
965, 885, 780, 600, 475 cmꢁ1; anal. calcd. for C17H31NO2
(281.4): C 72.55, H 11.10, N 4.98; found: C 72.46, H 11.00, N
4.88.
O-(1R,2S,5R)-5-Methyl-2-isopropylcyclohexyl N-tert-
Butyl Carbamate (33)
H2)a, 7.04 (d, 1H, J5,6 =8.4 Hz, 5-H), 7.14 (dd, 1H, J6,5
=
4
4
8.2 Hz, J6,2 =2.2 Hz, 6-H), 7.48 (d, 1H, J2,6 =2.0 Hz, 2-H),
a
This white solid (yield: 612 mg, 100%) was prepared from
(ꢁ)-menthol (10, 375 mg, 2.40 mmol) and N-tert-butyl isocy-
anate (21, 0.30 mL, 0.26 g, 2.6 mmol, 1.1 equiv.) in the pres-
8.73 and 9.47 ppm (2ꢄbr s, 2H, 2ꢄNH) assignments inter-
changeable; 13C NMR (100.63 MHz, DMSO): d=14.49 and
14.55 (C-2’, C-2’’), 17.07 (4-CH3), 59.96 and 60.04 (C-1’, C-
1’’), 114.90 (C-2, C-6), 125.51 (C-4), 130.12 (C-5), 136.43 and
137.17 (C-1, C-3), 153.46 and 154.23 ppm (2ꢄC=O); IR
ence of MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (8.4 mg, 24 mmol, 1.0 mol%) in 2 h
as described for 11; [a]D20: ꢁ47.98 (c 1.38, CHCl3); mp 508C.
1H NMR (400.13 MHz, CDCl3): d=0.60 (d, J2’,1’ =6.9 Hz,
3H, 2’-H3), 0.69 (d, 3H, J1’-CH3,1’ =7.1 Hz, 1’-CH3), 0.70 (d,
3H, J5-CH3,5 =6.5 Hz, 5-CH3), 0.61–0.95 (m, 3H), 1.11 (s, 9H,
t-Bu), 1.20–1.38 (m, 1H), 1.39–1.54 (m, 2H), 1.61–1.89 (m,
2H), 4.32 (mc, 1H), 4.54 ppm (br s, 1H, NH); 13C NMR
(100.63 MHz, CDCl3): d=16.49 (C-2’), 20.90 (1’-CH3), 22.11
˜
(ATR): n=3330, 3290, 2955, 2925, 2870, 1690, 1600, 1525,
1455, 1410, 1390, 1315, 1230, 1185, 1100, 1060, 1050, 1020,
985, 865, 775, 765, 745, 655, 560, 505, 460, 410 cmꢁ1; anal.
calcd. C13H18N2O4 (266.3): C 58.63, H 6.81, N 10.52; found:
C 58.60, H 6.67, N 10.41.
(5-CH3), 23.63 (C-3), 26.34 (C-1’), 29.10 [NC
ACHTUGNTRNEN(UNG CH3)3], 31.47
(C-5), 34.45 (C-4), 41.65 (C-6), 47.59 (C-2), 50.19 [NC-
˜
ACHTUNGTRENNUNG
O,Oꢀ-Diethyl 4,4’-Methylenebis(4,1-
phenylene)dicarbamate (40)[53]
MoO2Cl
finely ground under
(DMF)2 (1.9 mg, 5.5 mmol, 0.1 mol% rel. to 35) was
nitrogen atmosphere. CH2Cl2
a
(5.5 mL) and ethanol (35, 0.32 mL, 0.25 g, 5.5 mmol) were
added, followed at room temperature by 4,4’-methylenedi-
phenyl diisocyanate (37, 555 mg, 2.22 mmol, 0.40 equiv.).
After 1 h the reaction was quenched by the addition of ethyl
acetate (60 mL) and HCl(aq) (1 N, 20 mL). The aqueous
phase was extracted with ethyl acetate (2ꢄ50 mL). The
combined organic phases were washed with HCl(aq) (1N,
20 mL), saturated aqueous NaHCO3 solution (20 mL), and
brine (20 mL). and then dried over Na2SO4. Removal of the
solvent gave the dicarbamate 40 as a white solid; yield:
762 mg (100%); mp 121–1228C. 1H NMR (400.13 MHz,
DMSO): d=1.22 (t, 6H, J2’,1’ =7.1 Hz, 2ꢄ2’-H3), 3.77 (s, 2H,
Hbenzhydryl2), 4.09 (q, 4H, J1’,2’ =7.1 Hz, 2ꢄ1’-H2), AA’BBꢅ
signal centered at dA =7.08 and dB =7.34 (2H, A: 4ꢄ2-H,
B: 4ꢄ3-H), 9.47 ppm (s, 2H, 2ꢄNH); 13C NMR
(100.63 MHz, DMSO): d=14.80 (2ꢄC-2’), 39.76 (Cbenzhydryl),
59.97 (2ꢄC-1’), 118.31 (4 ꢄ C-3), 128.77 (4 ꢄ C-2), 135.37
and 137.09 (2 ꢄ C-1, 2 ꢄ C-4), 153.51 ppm (2ꢄC=O). IR
N,O-Di-tert-butyl Carbamate (34)
MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (8.3 mg, 24 mmol, 1.0 mol%) was finely
grounded under a nitrogen atmosphere. CH2Cl2 (0.48 mL)
and tert-butyl alcohol (16, 0.228 mL, 178 mg, 2.40 mmol)
were added, followed at room temperature by N-tert-butyl
isocyanate (21, 302 mL, 262 mg, 2.64 mmol, 1.2 equiv.). The
reaction was quenched after 2 h by the addition of H2O
(6 mL) and CH2Cl2 (12 mL). The aqueous phase was ex-
tracted with CH2Cl2 (3ꢄ12 mL). The combined organic
phases were dried over Na2SO4. Removal of the solvent
gave the carbamate 28 as a colorless oil, which solidified on
standing overnight; yield: 385 mg (93%); mp=39–418C.
1H NMR (400.13 MHz, CDCl3): d=1.28 (s, 9H, N-t-Bu),
1.42 (s, 9H, O-t-Bu), 4.45 ppm (br s, 1H, NH); 13C NMR
(100.63 MHz, CDCl3): d=28.55 [OC
ACHTUNGTRENNUNG
A
U
˜
(ATR): n=3340, 2950, 2925, 2870, 1695, 1595, 1520, 1455,
˜
(C=O); IR (ATR): n=3265, 3140, 3115, 2975, 2935, 1685,
1480, 1455, 1390, 1375, 1360, 1250, 1215, 1165, 1070, 1035,
955, 925, 855, 785, 770, 725, 655, 570, 460, 435 cmꢁ1; anal.
calcd. for C9H19NO2 (173.3): C 62.39, H 11.05, N 8.08;
found: C 62.30, H 11.18, N 7.80.
1410, 1390, 1370, 1305, 1225, 1180, 1065, 1050, 1020, 985,
970, 835, 815, 780, 765, 745, 625, 505, 470 cmꢁ1; anal. calcd.
for C19H22N2O4 (342.4): C 66.65, H 6.48, N 8.18; found: C
66.45, H 6.39, N 8.11.
14
asc.wiley-vch.de
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
(C-2’’’, C-2’’’’), 17.02 (4-CH3), 20.48 and 20.51 (1’’’-CH3, 1’’’’-
O,Oꢀ-Diethyl 3,5,5-Trimethylcyclohexane-1,3-
dicarbamate (41)[54]
CH3), 21.88 and 21.90 (5’-CH3, 5’’-CH3), 22.98 and 23.09 (C-
3’, C-3’’), 25.68 and 25.80 (C-1’’’, C-1’’’’), 30.90 (C-5’, C-5’’),
33.74 and 33.77 (C-4’, C-4’’), 41.11 and 41.17 (C-6’, C-6’’),
46.79 and 46.82 (C-2’, C-2’’), 73.27 and 73.36 (C-1’, C-1’’),
114.94 and 115.09 (C-2, C-6), 125.67 (C-4), 130.04 (C-5),
136.48 and 137.25 (C-1, C-3), 153.21 and 154.06 ppm (2ꢄC=
MoO2Cl
finely ground under
(DMF)2 (2.2 mg, 6.4 mmol, 0.1 mol% rel. to 35) was
nitrogen atmosphere. CH2Cl2
a
(6.4 mL) and ethanol (35, 0.38 mL, 0.30 g, 6.5 mmol) were
added, followed at room temperature by 3,5,5-cyclohexane-
1,3-diisocyanate (38, 0.54 mL, 0.57 g, 2.6 mmol, 0.40 equiv.).
After 1 h the reaction was quenched by the addition of ethyl
acetate (60 mL) and aqueous citric acid (10 wt%, 25 mL).
The aqueous phase was extracted with ethyl acetate (2ꢄ
50 mL). The combined organic phases were washed with
aqueous citric acid (10 wt%, 30 mL), saturated aqueous
NaHCO3-solution (20 mL), and brine (20 mL) and then
dried over Na2SO4. Removal of the solvent gave the dicar-
bamate 41 as a colorless resin; yield: 824 mg (101%).
1H NMR (400.13 MHz, CDCl3): d=0.69–0.82 (m, 3H), par-
tially superimposed by 0.75 (s, 3H, 3-CH3)a, 0.88 [s, 6H, 5-
(CH3)2]a, 0.99–1.10 (m, 7H, 2’-H3, 2’’-H3), 1.52 (mc, 2H), 2.73
(m, 2H, 3-CH2N), 3.47–3.69 (m, 1H, 1-H), 3.86–3.97 (m,
4H, 1’-H2, 1’’-H2), 4.91 (br d, 1H, J3-NH,3 =7.8 Hz, 3-NH),
˜
O); IR (ATR): n=3350, 2955, 2925, 2870, 1690, 1595, 1520,
1455, 1410, 1390, 1370, 1305, 1225, 1180, 1100, 1080, 1060,
1045, 1020, 985, 670, 835, 815, 780, 765, 625, 505, 470 cmꢁ1
;
anal. calcd. for C29H46N2O4 (486.7): C 71.57, H 9.53, N 5.76;
found: C 71.34, H 9.47, N 5.43.
O,Oꢀ-(1’R,2’S,5’R,1’’R,2’’S,5’’R)-Bis(5-methyl-2-
isopropylcyclohexyl) 4,4’-Methylenebis(4,1-
phenylene)dicarbamate (43)
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (2.2 mg, 6.4 mmol, 0.10 mol% rel. to 10)
was finely ground under a nitrogen atmosphere. (ꢁ)-Men-
thol (10, 1.00 g, 6.40 mmol) and CH2Cl2 (6.4 mL) were
added, followed at room temperature by 4,4’-methylenedi-
phenyl diisocyanate (37, 834 mg, 3.33 mmol, 0.52 equiv.).
Soon after the dissolution of the isocyanate the reaction got
cloudy and a white precipitate began to form. After 1 h the
reaction was quenched by the addition of CH2Cl2 (60 mL)
and HCl(aq) (1 N, 40 mL). The aqueous phase was extracted
with CH2Cl2 (3ꢄ40 mL). The combined organic phases were
washed with HCl(aq) (1 N, 20 mL), saturated aqueous
NaHCO3 solution (20 mL), and H2O (30 mL) and then dried
over Na2SO4. Removal of the solvent gave the dicarbamate
43 as a white solid; yield: 1.830 g (102%); [a]2D0: ꢁ74.08 (c
1.15, CHCl3); mp 121–1248C. 1H NMR (400.13 MHz,
DMSO): d=0.75 (d, 3H, J2’’,1’’ =6.9 Hz, 2’’-H3)a, 0.81–0.91
(m, 2H, 2ꢄ4’-H1), partially superimposed by 0.86 (d, 3 H
5.16 ppm (br t, 1H,
J1-CH2NH,1ꢁCH2 =6.3 Hz, 1-CH2NH)
a
assignment of one methyl group interchangeable;
13C NMR (100.63 MHz, CDCl3): d=14.32 and 14.35 (C-2’,
C-2’’), 22.92, 27.32, 31.46, 34.77, 36.12, 41.50, 44.14, 45.97,
46.76, 54.55, 60.03 and 60.27 (C-1’, C-1’’), 155.72 and
˜
156.91 ppm (2ꢄC=O); IR (film): n=3330, 3070, 2980, 2955,
2930, 2270, 1700, 1535, 1480, 1460, 1415, 1385, 1365, 1335,
1310, 1245, 1200, 1170, 1135, 1095, 1045, 865, 770, 755,
665 cmꢁ1; HR-MS (CI, NH3): m/z=315.22830 (ꢁ0.3 ppm),
calcd. for C16H31N2O4 (M+H+): 315.22838.
O,Oꢀ-(1’R,2’S,5’R,1’’R,2’’S,5’’R)-Bis(5-methyl-2-
isopropylcyclohexyl) 4-Methyl-1,3-
phenylenedicarbamate (42)
J
1’’-CH3,1’’ =7.0 Hz, 1’’-CH3)a and 0.87 (d, 6H, J5’-CH3,5’ =6.5 Hz,
2ꢄ5’-CH3)a, 0.93–1.09 (m, 2H, 2ꢄ6’-H1, 2ꢄ3’-H1), 1.33 (mc,
2H, approximately interpretable as dddd, J2’,1ꢅ ꢃJ2’,3’H(ax)
=
MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (2.3 mg, 6.7 mmol, 0.1 mol% rel. to 10) was
11.5 Hz, J2’,3’ꢁH(eq) ꢃJ2’,1’’ =2.8 Hz, 2ꢄ2’-H), 1.44 (mc, 2H, 2ꢄ
5’-H), 1.62 (mc, 4H, 2ꢄ3’-H2, 2ꢄ4’-H2), 1.91–2.01 (m, 4H,
2ꢄ1’’-H, 2ꢄ6’-H2), 3.77 (s, 2H, H2benzhydryl), 4.53 (ddd, 2H,
J1’,2ꢅ ꢃJ1’,6’-H(ax) =10.8 Hz, J1’,6’-H(eq) =4.2 Hz, 2ꢄ1’-H), AA’BBꢅ
signal centered at dA =7.05 and dB =7.37 (8H, A: 4ꢄ2-H,
B: 4ꢄ3-H), 9.45 ppm (br s, 2H, 2 ꢄ NH); 13C NMR
(100.63 MHz, DMSO): d=16.14, 20.49 and 21.84 (2ꢄC-2’’,
2ꢄ1’’-CH3, 2ꢄ5’-CH3), 22.96 (2ꢄC-3’), 25.66 (2ꢄC-1’’),
30.87 (2ꢄC-5’), 33.74 (2ꢄC-4’), 39.77 (Cbenzhydryl), 41.11 (2ꢄ
C-6’), 46.83 (2ꢄC-2’), 73.20 (2ꢄC-1’), 118.12 (4ꢄC-3),
128.70 (4ꢄC-2), 135.19 and 137.24 (2ꢄC-1, 2ꢄC-4),
finely ground under a nitrogen atmosphere. (ꢁ)-Menthol
(10, 1.047 g, 6.700 mmol) and CH2Cl2 (6.7 mL) were added,
followed at room temperature by 2,4-toluene diisocyanate
(36, 0.48 mL, 0.58 g, 3.4 mmol, 0.51 equiv.). Immediately, the
reaction mixture turned into an orange solution. After 1 h
the reaction was quenched by the addition of ethyl acetate
(60 mL) and aqueous citric acid (10 wt%, 24 mL). The aque-
ous phase was extracted with ethyl acetate (2ꢄ50 mL). The
combined organic phases were washed with aqueous citric
acid (10 wt%, 30 mL), saturated aqueous NaHCO3 solution
(20 mL), and brine (20 mL). and then dried over Na2SO4.
Removal of the solvent gave the dicarbamate 42 as a white
solid; yield: 1.626 mg (100%); [a]2D0: ꢁ89.88 (c 1.10, CHCl3);
mp 73–748C. 1H NMR (400.13 MHz, DMSO): d=0.76 (d,
3H, J2’’’,1’’’ =6.8 Hz, 2’’’-H3)a, partially superimposed by 0.77
(d, 3H, J2’’’’,1’’’’ =6.8 Hz, 2’’’’-H3)a, 0.83–0.91 (m, 14H, 4’-H1,
4’’-H1, 5’-CH3, 5’’-CH3, 1’’’-CH3, 1’’’’-CH3), 0.93–1.11 (m, 4H,
6’-H1, 6’’-H1, 3’-H1, 3’’-H1), 1.30–1.38 (m, 2H, 2’-H, 2’’-H),
1.40–1.52 (m, 2H, 5’-H, 5’’-H), 1.59–1.69 (m, 4H, 3’-H2, 3’’-
H2, 4’-H2, 4’’-H2), 1.92–2.01 (m, 4H, 1’’’-H, 1’’’’-H, 6’-H2, 6’’-
˜
153.22 ppm (2ꢄC=O); IR (ATR): n=3350, 2950, 2925,
2865, 1690, 1595, 1520, 1455, 1410, 1390, 1370, 1305, 1225,
1180, 1105, 1060, 1050, 1020, 985, 970, 815, 780, 765, 625,
545, 505, 470 cmꢁ1; anal. calcd. for C35H50N2O4 (562.8): C
74.70, H 8.95, N 4.98; found: C 74.61, H 8.88, N 4.84.
O,Oꢀ-(1’R,2’S,5’R,1’’R,2’’S,5’’R)-Bis(5-methyl-2-
isopropylcyclohexyl) 1,5,5-Trimethylcyclohexane-1,3-
dicarbamate (44)
H2), 2.09 (s, 3H, 4-CH3), 4.47–4.56 (m, 2H, 1’-H, 1’’-H), 7.03
4
(d, 1H, J5,6 =8.5 Hz, 5-H), 7.12 (dd, 1H, J6,5 =8.3 Hz, J6,2
=
MoO2Cl2ACTHUNGRETNNU(G DMF)2 (1.8 mg, 5.2 mmol, 0.10 mol% rel. to 10)
1.9 Hz, 6-H), 7.49 (d, 1H, 4J2,a6 =2.1 Hz, 2-H), 8.69 and
9.44 ppm (2 ꢄ br s, 2H, 2 ꢄ NH) assignments interchangea-
ble; 13C NMR (100.63 MHz, DMSO): d=16.18 and 16.29
was finely ground under a nitrogen atmosphere. (ꢁ)-Men-
thol (10, 818 mg, 5.23 mmol) and CH2Cl2 (5.2 mL) were
added, followed at room temperature by isophorone diiso-
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
15
ÞÞ
These are not the final page numbers!

Christian Stock and Reinhard Brꢀckner
FULL PAPERS
cyanate (38, 0.55 mL, 0.58 g, 2.6 mmol, 0.50 equiv.). After
1 h the reaction was quenched by the addition of ethyl ace-
tate (60 mL) and aqueous citric acid (10 wt%, 25 mL). The
aqueous phase was extracted with ethyl acetate (2ꢄ50 mL).
The combined organic phases were washed with aqueous
citric acid (10 wt%, 30 mL), saturated aqueous NaHCO3 so-
lution (20 mL), and brine (20 mL) and then dried over
Na2SO4. Removal of the solvent gave the dicarbamate 44 as
a colorless solid; yield: 1.404 g (100%); [a]2D0: ꢁ60.88 (c 1.17,
CHCl3); mp 105–1078C. 1H NMR (400.13 MHz, DMSO):
d=0.70–0.74 (m, 6H, 2’’’-H3, 2’’’’-H3), 0.75–1.12 [m, 31H, 5’-
CH3, 5’’-CH3, 1’’’-CH3, 1’’’’-CH3, 1-CH3, 5-(CH3)2, 4’-H1, 4’’-
H1, 3’-H1, 3’’-H1, 6’-H1, 6’’-H1], 1.19–1.31 (m, 2H, 2’-H, 2’’-
H), 1.33–1.47 (m, 4H, 5’-H, 5’’-H), 1.55–1.66 (m, 4H, 3’-H2,
3’’-H2, 4’-H2, 4’’-H2), 1.82–1.97 (m, 1’’’-H, 1’’’’-H, 6’-H2, 6’’-
H2), 2.71 (mc, 2H, 3-CH2N), 3.56 (mc, 1H, 1-H), 4.32–4.46
(m, 2H, 1’-H, 1’’-H), 6.82 (br d, 1H, J1-NH,1 =7.3, 1-NH),
O,Oꢀ-Di-tert-butyl 4,4’-Methylenebis(4,1-
phenylene)dicarbamate (46)
MoO2Cl
finely ground under
(DMF)2 (9.2 mg, 27 mmol, 1.0 mol% rel. to 16) was
nitrogen atmosphere. CH2Cl2
a
(2.7 mL) and tert-butyl alcohol (16, 0.26 mL, 0.20 g,
2.7 mmol) were added, followed at room temperature by
4,4’-methylenediphenyl diisocyanate (37, 274 mg, 1.09 mmol,
0.40 equiv.). After 1 h the reaction was quenched by the ad-
dition of ethyl acetate (60 mL) and HCl(aq) (1N, 20 mL). The
aqueous phase was extracted with ethyl acetate (2ꢄ50 mL).
The combined organic phases were washed with HCl(aq)
(1N, 20 mL), saturated aqueous NaHCO3 solution (20 mL),
and brine (20 mL) and then dried over Na2SO4. Removal of
the solvent gave the dicarbamate 46 as a white solid; yield:
429 mg (100%); mp 163–1648C. 1H NMR (400.13 MHz,
DMSO): d=1.45 (s, 18H, 2ꢄt-Bu), 3.76 (s, 2H, Hbenzhydryl2),
AA’BBꢅ signal centered at dA =7.04 and dB =7.32 (8H, A:
4ꢄ2-H, B: 4ꢄ3-H), 9.19 ppm (s, 2H, 2ꢄNH); 13C NMR
6.99 ppm (br t, 1H,
J3-CH2NH,3-CH2N =6.1, 3-CH2NH);
13C NMR (100.63 MHz, CDCl3): d=16.24, 20.49 and 21.89
(5’-CH3, 5’’-CH3, C-2’’’, C-2’’’’, 1’’’-CH3, 1’’’’-CH3), 23.08 (5-
C1H3)a, 23.15 (C-3’), 25.68 (C-1’’’, C-1’’’’), 27.50 (5-C2H3)a,
30.88 (C-5’, C-5’’), 31.32 (3-CH3)a, 33.83 (C-4’), 34.92, 36.38,
41.33, 43.70, 45.14, 46.79, 46.84, 46.99, 54.31, 72.54 and 72.57
(100.63 MHz, DMSO): d=28.10 [C
78.78 [C(CH3)3], 118.24 (4ꢄC-3), 128.67 (4ꢄC-2), 135.11
and 137.36 (2ꢄC-1, 2ꢄC-4), 152.76 ppm (2ꢄC=O); IR
(CH3)3], 39.75 (Cbenzhydryl),
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
˜
(ATR): n=3335, 2955, 2925, 2870, 1690, 1595, 1520, 1455,
a
1410, 1390, 1370, 1310, 1230, 1180, 1160, 1050, 1020, 985,
970, 920, 840, 810, 780, 765, 740, 645, 505, 470 cmꢁ1; anal.
calcd. for C19H22N2O4 (342.4): C 66.65, H 6.48, N 8.18;
found: C 66.45, H 6.39, N 8.11.
(C-1’, C-1’’), 156.60 and 156.62 ppm (2 ꢄ C=O) assignment
˜
interchangeable; IR (film): n=3345, 3335, 2955, 2925, 2870,
2360, 2345, 1700, 1515, 1455, 1400, 1385, 1370, 1340, 1305,
1240, 1180, 1135, 1080, 1030, 985, 920, 845, 770, 665 cmꢁ1
;
anal. calcd. for C32H58N2O4 (534.8): C 71.87, H 10.93, N
5.24; found: C 71.66, H 10.81, N 4.82; HR-MS (CI, NH3): m/
z=535.44770 (+0.4 ppm), calcd. for C32H59N2O4 (M+H+):
535.44748.
O,Oꢀ-Di-tert-butyl 3,5,5-Trimethylcyclohexane-1,3-
dicarbamate (47)
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (16.2 mg, 47.0 mmol, 1.0 mol% rel. to 16)
was finely ground under a nitrogen atmosphere. CH2Cl2
(4.7 mL) and tert-butyl alcohol (16, 0.45 mL, 0.35 g,
4.7 mmol) were added, followed at room temperature by
3,5,5-trimethylcyclohexane-1,3-diisocyanate (38, 0.39 mL,
0.42 g, 1.9 mmol, 0.40 equiv.). After 1 h the reaction was
quenched by the addition of ethyl acetate (60 mL) and
aqueous citric acid (10 wt%, 25 mL). The aqueous phase
was extracted with ethyl acetate (2ꢄ50 mL). The combined
organic phases were washed with aqueous citric acid (10
wt%, 30 mL), saturated aqueous NaHCO3 solution (20 mL),
and brine (20 mL) and then dried over Na2SO4. Removal of
the solvent gave the dicarbamate 47 as a colorless solid;
O,O’-Di-tert-butyl 4-Mthyl-1,3-phenylenedicarbamate
(45)
MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (15.9 mg, 46.1 mmol, 1.0 mol% rel. to 16)
was finely ground under a nitrogen atmosphere. CH2Cl2
(4.6 mL) and tert-butyl alcohol (16, 0.44 mL, 0.34 g,
4.6 mmol) were added, followed at room temperature by
2,4-toluene diisocyanate (36, 0.26 mL, 0.32 g, 1.8 mmol,
0.4 equiv.). After 1 h the reaction was quenched by the addi-
tion of ethyl acetate (60 mL) and aqueous citric acid (10
wt%, 24 mL). The aqueous phase was extracted with ethyl
acetate (2ꢄ50 mL). The combined organic phases were
washed with aqueous citric acid (10 wt%, 30 mL), saturated
aqueous NaHCO3 solution (20 mL), and brine (20 mL) and
then dried over Na2SO4. Removal of the solvent gave the di-
carbamate 45 as a white solid; yield: (564 mg (97%); mp
134–1368C. 1H NMR (400.13 MHz, DMSO): d=1.445 and
1
yield: 675.2 mg (97%); mp 65–688C. H NMR (400.13 MHz,
CDCl3): d=0.76–1.09 (m, 6H), partially superimposed by:
0.85 (s, 3H, 3-CH3)a, 0.90 (s, 3H, 5-C1H3)a and 0.97 (s, 3H,
5-C2H3)a, 1.37 (s, 18H, 2ꢄt-Bu), 2.60–2.68 (m, 2H, 3-CH2N),
3.43–3.58 (m, 1H, 1-H), 6.62 (br d, 1H, J3-NH,3 =8.0 Hz, 3-
NH), 6.75 ppm (br t, 1H, J1-CH2NH,1-CH2 =6.3 Hz, 1-CH2N)
a
assignments interchangeable; 13C NMR (100.63 MHz,
CDCl3): d=23.05, 27.49, 28.21 and 28.72 [1’-(CH3)3, 1’’-
(CH3)3], 31.36, 34.97, 36.25, 41.40, 43.32, 45.44, 46.79, 53.84,
77.25 (C-1’, C-1’’), 154.75 and 156.09 ppm (2ꢄC=O): IR
1.453 (2 ꢄ s, 18H, 2ꢄt-Bu), 2.09 (s, 3H, 4-CH3), 7.00 (d, 1H,
4
J
5,6 =8.6 Hz, 5-H), 7.09 (dd, 1H, J6,5 =8.3 Hz, J6,2 =2.2 Hz, 6-
4
H), 7.46 (d, 1H, J2,6 =2.1 Hz, 2-H), 8.41 and 9.18 ppm (2 ꢄ
br s, 2H, 2ꢄNH); 13C NMR (100.63 MHz, DMSO): d=
˜
(ATR): n=3330, 2960, 2930, 2870, 1690, 1600, 1525, 1455,
1410, 1390, 1365, 1310, 1270, 1235, 1160, 1050, 1020, 885,
865, 815, 795, 780, 765, 655, 560, 510, 460 cmꢁ1; HR-MS (CI,
NH3): m/z=416.25510 (+0.4 ppm), calcd. for C22H29N2O4
17.11 (4-CH3), 28.10 [2ꢄC
(CH3)3], 114.75 and 114.93 (C-2, C-6), 125.29 (C-4), 129.90
(C-5), 136.57 and 137.38 (C-1, C-3), 152.71 and 153.41 ppm
ACHTUNGTREN(NNUG CH3)3], 78.50 and 78.72 [2ꢄC-
ACHTUNGTRENNUNG
+
(M+NH4 ): m/z=416.25493.
˜
(2ꢄC=O); IR (ATR): n=3285, 2960, 2930, 2870, 1690, 1600,
1525, 1455, 1410, 1390, 1365, 1310, 1290, 1235, 1160, 1050,
1000, 885, 870, 815, 780, 765, 745, 655, 560, 505, 460 cmꢁ1
;
anal. calcd. for C17H26N2O4 (322.4): C 63.33, H 8.13, N 8.69;
found: C 63.20, H 7.87, N 9.02.
16
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
1,8-Bis(N-phenylcarbamoyloxy)octane (51)
2,5-Dimethyl-2,5-bis-(N-phenylcarbamoyloxy)hexane
(53)
MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (3.2 mg, 9.3 mmol, 0.2 mol% rel. to 48) was
finely ground under a nitrogen atmosphere. 1,8-Octanediol
(48, 680 mg, 4.65 mmol) and CH2Cl2 (9.3 mL) were added.
The resulting suspension was slightly warmed to effect com-
plete dissolution of the diol. Then, N-phenyl isocyanate (2,
1.11 mL, 1.22 g, 10.2 mmol, 2.2 equiv,) was added to the so-
lution. After 2 min the reaction solution had significantly
warmed and solidified abruptly 1 min later. After all in all
10 min the reaction mixture was suspended in ethyl acetate
(200 mL) and washed with aqueous citric acid (10 wt%, 2ꢄ
25 mL), saturated aqueous NaHCO3 solution (40 mL), and
brine (30 mL). Drying over Na2SO4 and removal of the sol-
vent gave the dicarbamate 51 as a colorless solid; yield:
1.846 g (103%); mp=151–1538C. 1H NMR (400.13 MHz,
DMSO): d=1.28–1.40 (m, 8H, 3-H2, 4-H2, 5-H2, 6-H2), 1.61
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (19.3 mg, 55.9 mmol, 2.0 mol% rel. to 50)
was finely ground under a nitrogen atmosphere. 2,5-Dimeth-
yl-2,5-hexanediol (50, 409 mg, 2.80 mmol) and DMF
(5.6 mL) were added and the mixture was heated to 608C,
whereupon all components dissolved. Then, N-phenyl isocy-
anate (2, 0.67 mL, 0.73 g, 6.2 mmol, 2.2 equiv.) was added at
this temperature in one portion. After 30 min the reaction
was quenched by the addition of H2O (29 mL) and EtOAc
(66 mL). The aqueous phase was extracted with EtOAc (3ꢄ
60 mL). The cloudy combined organic phases were heated
to reflux and dried over Na2SO4 and filtered hot. Removal
of the solvent gave the carbamate 39 as a white solid; yield:
1.05 g (98%); mp 192–1938C (sublimation). 1H NMR
(400.13 MHz, acetone): d=1.47 (s, 12H, 4ꢄCH3), 1.92 (s,
4H, 2ꢄCH2), ABB’CCꢅ signal centered at dA =6.97, dB =
7.24 and dC =7.51 (10H, A: 2ꢄHpara, B: 4ꢄHmeta, C: 4ꢄ
Hortho), 8.36 ppm (br s, 2H, 2ꢄNH); 13C NMR (100.63 MHz,
acetone): d=26.63 (4ꢄCH3), 35.60 (C-3, C-4), 81.82 (C-2,
C-5), 119.13 (4ꢄCortho), 123.05 (2ꢄCpara), 129.47 (4ꢄCmeta),
(tt, 4H, J2,1 ꢃ J2,3 =6.9 Hz, 2-H2, 7-H2), 4.05 (t, 4H, J1,2
6.6 Hz, 1-H2, 8-H2), 6.96 (mc, 2H, approximately interpreta-
ble as tt,
para,meta =7.4 Hz, 4Jpara,ortho =1.1 Hz, 2ꢄHpara),
AA’BBꢅ signal centered at dA =7.25 and dB =7.44 (8H, A:
=
J
4ꢄHmeta
,
B: 4ꢄHortho), 9.55 ppm (br s, 2H, 2ꢄNH);
13C NMR (100.63 MHz, DMSO): d=25.28 (C-3, C-6), 28.48
and 28.59 (C-4/5 and C-2/7), 64.04 (C-1, C-8), 118.10 (4ꢄ
Cortho), 122.21 (2ꢄCpara), 128.64 (4ꢄCmeta), 139.18 (2ꢄCipso),
140.58 (2ꢄCipso), 153.60 ppm (2ꢄC=O); IR (ATR): n=3330,
˜
3140, 3045, 2980, 1735, 1705, 1655, 1600, 1535, 1500, 1445,
1385, 1215, 1065, 1030, 920, 900, 850, 750, 690, 665, 510,
410 cmꢁ1; anal. calcd. for C22H28N2O4 (384.5): C 68.73, H
7.34, N 7.29; found: C 68.75, H 7.26, N 7.27.
˜
153.89 ppm (2ꢄC=O); IR (ATR): n=3325, 3135, 3060,
2935, 2860, 1735, 1705, 1655, 1600, 1535, 1500, 1445, 1385,
1315, 1215, 1060, 1030, 920, 900, 850, 840, 745, 690, 665,
505 cmꢁ1; anal. calcd. for C22H28N2O4 (384.5): C 68.73, H
7.34, N 7.29; found: C 68.02, H 7.22, N 7.00; HR-MS (CI,
1,8-Bis(N-tert-butylcarbamoyloxy)octane (54)
NH3):m/z=385.21290
(+0.4 ppm),
calculated
for
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (9.4 mg, 27 mmol, 1.0 mol% rel. to 48) was
C22H29N2O4 (M+H+): 385.21273.
finely ground under a nitrogen atmosphere. 1,8-Octanediol
(48, 401 mg, 2.74 mmol) and CH2Cl2 (5.4 mL) were added.
The resulting suspension was slightly warmed to effect com-
plete dissolution of the diol. Then, N-tert-butyl isocyanate
(21, 0.68 mL, 0.59 g, 6.0 mmol, 2.2 equiv.) was added to the
solution. After 30 min the reaction was quenched by the ad-
dition of ethyl acetate (60 mL) and aqueous citric acid (10
wt%, 20 mL). The aqueous phase was extracted with ethyl
acetate (2ꢄ60 mL). The combined organic phases were
washed with aqueous citric acid (10 wt%, 20 mL), saturated
aqueous NaHCO3 solution (20 mL), and brine (20 mL) and
then dried over Na2SO4. Removal of the solvent gave the di-
carbamate 54 as a colorless solid; 921.5 mg (98%); mp 64–
2,2-Dimethyl-1,3-bis-(N-phenylcarbamoyloxy)propane
(52)
MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (7.1 mg, 21 mmol, 0.20 mol% rel. to 49)
was finely ground under a nitrogen atmosphere. 2,2-Dime-
thylpropanediol (49, 1.094 g, 10.50 mmol) and CH2Cl2
(21 mL) were added, followed at room temperature by N-
phenyl isocyanate (2, 2.51 mL, 2.75 g, 23.1 mmol, 2.2 equiv.).
After 1 h the reaction was quenched by the addition of H2O
(256 mL) and CH2Cl2 (50 mL). The aqueous phase was ex-
tracted with CH2Cl2 (3ꢄ40 mL). The combined organic
phases were dried over Na2SO4. Removal of the solvent
gave the carbamate 52 as a white solid; yield: 3.61 g
1
668C. H NMR (400.13 MHz, CDCl3): d=1.29–1.37 (m, 8H,
3-H2, 4-H2, 5-H2, 6-H2), partially superimposed by 1.31 (s,
1
(101%); mp 128–1308C. H NMR (400.13 MHz, CDCl3): d=
18H, 2ꢄt-Bu), 1.58 (mc, 4H, 2-H2, 7-H2), 3.98 (t, 4H, J1,2
=
6.6 Hz, 1-H2, 8-H2), 4.59 ppm (br s, 2H, 2ꢄNH); 13C NMR
1.02 [s, 6H, 2-(CH3)2], 4.02 (s, 4H, 1-H2, 3-H2), 6.79 (br s,
2H, 2 ꢄ NH), 7.06 (mc, 2H, approximately interpretable as
(100.63 MHz, CDCl3): d=25.92 (C-3, C-5), 29.11 [2ꢄC-
ACHUTNGRENU(NG CH3)3], 29.24 (C-2, C-4, C-5, C-7), 50.29 [2ꢄCACHTUNGTRENNUNG(CH3)3],
tt,
J
para,meta =7.3 Hz, 4Jpara,ortho =1.2 Hz, 2ꢄHpara), AA’BB’
signal centered at dA =7.30 and dB =7.38 ppm (8H, A: 4ꢄ
Hmeta, B: 2ꢄHortho); 13C NMR (100.63 MHz, CDCl3): d=
21.78 [2-(CH3)2], 35.12 (C-2), 69.99 (C-1, C-3), 118.81 (4ꢄ
Cortho), 123.59 (2ꢄCpara), 129.12 (4ꢄCmeta), 137.84 (2ꢄCipso),
˜
64.31 (C-1, C-8), 155.34 ppm (2ꢄC=O); IR (ATR): n=3325,
3060, 2950, 2930, 2855, 1695, 1655, 1600, 1535, 1500, 1445,
1385, 1360, 1315, 1270, 1215, 1090, 1030, 925, 900, 850, 745,
730, 690, 630, 495 cmꢁ1.
˜
153.64 ppm (2ꢄC=O); IR (ATR): n=3295, 3140, 3065,
2965, 2885, 1700, 1600, 1535, 1500, 1445, 1315, 1230, 1155,
1085, 1065, 1030, 930, 905, 850, 755, 725, 690, 625, 505,
425 cmꢁ1; anal. calcd. for C19H22N2O4 (342.4): C 66.65, H
6.48, N 8.18; found: C 66.77, H 6.56, N 8.08.
2,2-Dimethyl-1,3-bis-(N-tert-
butylcarbamoyloxy)propane (55)
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (9.2 mg, 27 mmol, 1.0 mol% rel. to 49) was
finely ground under a nitrogen atmosphere. 2,2-Dimethyl-
propanediol (49, 284 mg, 2.73 mmol) and CH2Cl2 (5.4 mL)
were added, followed at room temperature by N-tert-butyl
isocyanate (21, 0.68 mL, 0.59 g, 5.9 mmol, 2.2 equiv.). The re-
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
17
ÞÞ
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Christian Stock and Reinhard Brꢀckner
FULL PAPERS
sulting solution was suspended in a preheated oilbath and
heated at reflux. After 2 h the reaction was quenched by the
addition of ethyl acetate (60 mL) and aqueous citric acid (10
wt%, 20 mL). The aqueous phase was extracted with ethyl
acetate (2ꢄ60 mL). The combined organic phases were
washed with aqueous citric acid (10 wt%, 30 mL), saturated
aqueous NaHCO3 solution (20 mL), and brine (20 mL) and
then dried over Na2SO4. Removal of the solvent gave the di-
carbamate 55 as a white solid; 821 mg (99%); mp 114–
4.8 Hz, 2ꢄ1-H2), 3.65 (br s, 4H, 2ꢄ2-H2), 4.65 (br s, 2H, 2ꢄ
OH), ABB’CC’ signal centered at dA =7.00 and dB,C =7.25
(5H, A: Hpara, B and C: 2ꢄHortho, 2ꢄHmeta), 8.69 ppm (br s,
1H, NH); 13C NMR (100.63 MHz, CDCl3): d=51.20 (2ꢄC-
1), 61.50 (2ꢄC-2), 119.59 (2ꢄCortho), 122.76 (Cpara), 128.88
(2ꢄCmeta), 139.36 (Cipso), 159.17 ppm (C=O); IR (ATR): n=
˜
3310, 2935, 2880, 2360, 2340, 1645, 1595, 1550, 1500, 1470,
1445, 1405, 1370, 1255, 1225, 1175, 1125, 1075, 1040, 875,
755, 695 cmꢁ1
;
HR-MS (CI, NH3): m/z=225.12380
1
1168C. H NMR (400.13 MHz, DMSO): d=0.87 (s, 6H, 2ꢄ
(ꢁ0.5 ppm), calcd. for C11H17N2O3 (M+H+): 225.12392.
CH3), 1.21 (s, 18H, 2ꢄt-Bu), 3.69 (br s, 4H, 2ꢄCH2),
6.76 ppm (br s, 2H, 2ꢄNH); 13C NMR (100.63 MHz,
N,N-Bis[2-(N’’-phenylcarbamoyloxy)ethyl]-N’-
phenylurea (58)
DMSO): d=21.36 (2-CH3), 28.58 [2ꢄC
ACHTUGNTRENUN(NG CH3)3], 34.90 (2-C),
49.19 [2ꢄC(CH3)3], 68.06 (C-1, C-3), 154.80 ppm (2ꢄC=O);
ACHTUNGTRENNUNG
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (4.2 mg, 12 mmol, 0.3 mol% rel. to 59) was
˜
IR (ATR): n=3330, 2970, 1700, 1660, 1600, 1525, 1480,
1445, 1385, 1360, 1315, 1265, 1210, 1085, 1030, 950, 920, 850,
750, 690, 590, 510, 465, 430 cmꢁ1; anal. calcd. for C15H30N2O4
(302.4): C 59.58, H 10.00, N 9.26; found: C 59.59, H 10.14, N
9.10.
finely ground under a nitrogen atmosphere. An emulsion of
diethanolamine (59, 421 mg, 4.00 mmol) in CH2Cl2 (8.0 mL)
was added. N-Phenyl isocyanate (1.43 mL, 1.57 g,
13.2 mmol, 3.3 equiv.) was added dropwise at room tempera-
ture to this mixture. After the first drops the reaction
cleared up. After 30 min the reaction mixture was quenched
by the addition of ethyl acetate (60 mL) and aqueous citric
acid (10 wt%, 20 mL). The aqueous phase was extracted
with ethyl acetate (2ꢄ50 mL). The combined organic phases
were washed with aqueous citric acid (10 wt%, 20 mL), satu-
rated aqueous NaHCO3 solution (20 mL), and brine
(20 mL). Drying over Na2SO4 and removal of the solvent
gave the urea 58 as a voluminous colorless powder; yield:
1.802 g (97%); mp=84–858C. 1H NMR (400.13 MHz,
DMSO): d=3.71 (t, 2H, J1,2 =5.8 Hz, 2ꢄ1-H2), 4.24 (t, 4H,
2,5-Dimethyl-2,5-bis-(N-tert-
butylcarbamoyloxy)hexane (56)
MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (14.3 mg, 41.4 mmol, 2.0 mol% rel. to 50)
was finely ground under a nitrogen atmosphere. 2,5-Dimeth-
yl-2,5-hexanediol (50, 303 mg, 2.07 mmol) and CH2Cl2
(4.1 mL) were added followed at room temperature by N-
tert-butyl isocyanate (21, 0.52 mL, 0.45 g, 4.6 mmol,
2.2 equiv). The resulting solution was suspended in a pre-
heated oilbath and heated at reflux. After 4 h the reaction
was quenched by the addition of ethyl acetate (60 mL) and
aqueous citric acid (10 wt%, 20 mL). The aqueous phase
was extracted with ethyl acetate (2ꢄ60 mL). The combined
organic phases were washed with aqueous citric acid (10
wt%, 30 mL), saturated aqueous NaHCO3 solution (20 mL),
and brine (20 mL) and then dried over Na2SO4. Removal of
the solvent gave the dicarbamate 56 as a white solid; yield:
668 mg (94%); mp 154–1558C. 1H NMR (499.50 MHz,
DMSO, T=363 K): d=1.22 (s, 18H, 2ꢄt-Bu), 1.35 (s, 12H,
4ꢄCH3), 1.76 (s, 4H, 2ꢄCH2), 5.90 ppm (br s, 2H, 2ꢄNH);
13C NMR (125.61 MHz, DMSO, T=363 K): d=25.88 (4ꢄ
J
2,1 =5.8 Hz, 2ꢄ2-H2), 6.94 (mc, 1H, Hpara), partially superim-
posed by 6.98 (mc, 2H, 2ꢄHpara’), 7.21 (mc, 2H, 2ꢄHmeta),
partially superimposed by 7.26 (mc, 4H, 4ꢄHmeta’), 7.42–7.48
(m, 6H, 2ꢄHortho, 4ꢄHortho’), 8.34 [br s, 1H, NHC(=O)N],
9.64 ppm
[br
s,
2H,
2ꢄNHC(=O)O];
13C NMR
(100.63 MHz, DMSO): d=51.20 (2ꢄC-1), 61.50 (2ꢄC-2),
118.38 (4ꢄCortho’), 120.26 (2ꢄCortho), 122.00 (Cpara), 122.46
(2ꢄCpara’), 128.15 (2ꢄCmeta), 128.67 (4ꢄCmeta’), 139.95 (2ꢄ
Cipso), 140.15 (Cipso), 153.43 [2ꢄNHC(=O)O], 154.83 ppm
˜
[NHC(=O)N]; IR (ATR): n=3300, 3135, 3060, 2960, 1705,
1645, 1600, 1525, 1500, 1445, 1390, 1315, 1215, 1155, 1065,
CH3), 28.34 [2ꢄC
N
1030, 900, 835, 750, 690, 505 cmꢁ1
; anal. calcd. for
A
C25H26N4O5 (462.5): C 64.92, H 5.67, N 12.11; found C 64.56,
H 5.70, N 11.98.
˜
n=3330, 2975, 2935, 1710, 1685, 1600, 1525, 1450, 1390,
1380, 1360, 1285, 1200, 1155, 1105, 1075, 940, 875, 785, 750,
690, 610, 505, 465 cmꢁ1; HR-MS (CI, NH3): m/z=345.27520
(ꢁ0.4 ppm), calcd. for C18H37N2O4 (M+H+): 345.27533.
N,N-Bis(2-hydroxyethyl)-N’-tert-butylurea (60)
N-tert-Butyl isocyanate (0.26 mL, 0.22 g, 2.2 mmol,
1.0 equiv.) was added at room temperature to an emulsion
of diethanolamine (59, 235.4 mg, 2.239 mmol) in CH2Cl2
(2.2 mL). Thereupon the reaction cleared up and got warm.
After 15 min the reaction mixture was quenched by the ad-
dition of ethyl acetate (60 mL) and aqueous citric acid (10
wt%, 16 mL). The aqueous phase was extracted with ethyl
acetate (3ꢄ60 mL). The combined organic phases were
washed with saturated aqueous NaHCO3-solution (20 mL)
and brine (15 mL). Drying over Na2SO4 and removal of the
solvent gave the urea 60 as a voluminous colorless powder;
yield: 402.8 mg (88%); mp 115–1168C. 1H NMR
(400.13 MHz, CDCl3): d=1.31 (s, 9H, t-Bu), 3.37 (t, 4H,
N,N-Bis(2-hydroxyethyl)-N’-phenylurea (57)
N-Phenyl isocyanate (0.54 mL, 0.60 g, 5.0 mmol, 1.0 equiv.)
was added at roomt temperature to an emulsion of dietha-
nolamine (59, 526 mg, 5.00 mmol) in CH2Cl2 (5.0 mL). Im-
mediately the reaction mixture started to boil, which subsid-
ed after some seconds. After 1 min the reaction mixture was
quenched by the addition of ethyl acetate (60 mL) and
aqueous citric acid (10 wt%, 24 mL). The aqueous phase
was extracted with ethyl acetate (2ꢄ60 mL). The combined
organic phases were washed with saturated aqueous
NaHCO3-solution (16 mL) and brine (12 mL). Drying over
Na2SO4 and removal of the solvent gave the urea 57 as a vol-
J
J
1,2 =4.7 Hz, 2ꢄ1-H2), 3.67 (br s, 2H, 2ꢄOH), 3.74 (t, 4H,
uminous colorless powder; yield: 1.14 g (102%); mp 69–
708C. H NMR (400.13 MHz, CDCl3): d=3.37 (t, 4H, J1,2
2,1 =4.8 Hz, 2ꢄ2-H2), 5.91 ppm (br s, 1H, NH); 13C NMR
1
=
(100.63 MHz, CDCl3): d=29.44 [CACHTGNURTENNU(G CH3)3], 50.66 [CACHTUNGTRENNUNG(CH3)3],
18
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Adv. Synth. Catal. 0000, 000, 0 – 0
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
˜
51.02 (2ꢄC-1), 62.01 (2ꢄC-2), 160.95 ppm (C=O); IR
153.34 ppm (2ꢄC=O); IR (ATR): n=3345, 3065, 2970,
2900, 1700, 1600, 1525, 1500, 1445, 1315, 1210, 1085, 1065,
1030, 940, 920, 900, 850, 755, 740, 690, 630, 615, 500 cmꢁ1.
˜
(ATR): n=3385, 3325, 2970, 2935, 2900, 1710, 1685, 1600,
1560, 1535, 1475, 1450, 1410, 1390, 1360, 1285, 1155, 1055,
940, 880, 770, 610, 575, 515, 465, 415 cmꢁ1; anjal. calcd. for
C9H20N2O3 (204.3): C 52.92, H 9.87, N 13.71; found: C 53.09,
H 9.91, N 13.84.
1,1,1-Tris[(N-tert-butylcarbamoyloxy)methyl]ethane
(65)
N,N-Bis[2-(N’’-tert-butylcarbamoyloxy)ethyl]-N’-tert-
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (9.3 mg, 27 mmol, 1.5 mol% rel. to 62) was
butylurea (61)
finely ground under a nitrogen atmosphere. 1,1,1-Tris(hy-
droxymethyl)ethane (62, 216 mg, 1.80 mmol) was added and
the mixture suspended in (CH2Cl)2 (5.5 mL). N-tert-Butyl
isocyanate (21, 0.68 mL, 0.59 g, 5.9 mmol, 3.3 equiv.) was
added at room temperature and the mixture was heated to
reflux giving a greenish solution. After 2 h the reaction mix-
ture was quenched by the addition of ethyl acetate (60 mL)
and aqueous citric acid (10 wt%, 20 mL). The aqueous
phase was extracted with ethyl acetate (2ꢄ60 mL). The
combined organic phases were washed with aqueous citric
acid (10 wt%, 30 mL), saturated aqueous NaHCO3 solution
(20 mL), and brine (20 mL). Drying over Na2SO4 and re-
moval of the solvent gave the tricarbamate 65 as a colorless
solid; yield: 769.6 mg (102%); mp 165–1668C. 1H NMR
(400.13 MHz, DMSO): d=0.88 (br s, 3H, 2-H3), 1.20 (s,
27H, 3ꢄt-Bu), 3.79 (br s, 6H, 3ꢄCH2), 6.81 ppm (br s, 3H,
3ꢄNH); 13C NMR (100.63 MHz, DMSO): d=16.43 (2-C),
MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (20.7 mg, 60.1 mmol, 2.0 mol% rel. to 59)
was finely ground under a nitrogen atmosphere. An emul-
sion of diethanolamine (59, 316.2 mg, 3.007 mmol) in
CH2Cl2 (6.0 mL) was added. N-tert-Butyl isocyanate
(1.13 mL, 983 mg, 9.92 mmol, 3.3 equiv.) was added at room
temperature and the reaction mixture was heated to reflux
with a preheated oilbath. After 1 min a voluminous precipi-
tate had formed, which gradually dissolved over the next
30 min. After all in all 4 h the reaction mixture was
quenched by the addition of ethyl acetate (60 mL) and
aqueous citric acid (10 wt%, 20 mL). The aqueous phase
was extracted with ethyl acetate (2ꢄ50 mL). The combined
organic phases were washed with aqueous citric acid (10
wt%, 20 mL), saturated aqueous NaHCO3 solution (20 mL),
and brine (20 mL). Drying over Na2SO4 and removal of the
solvent gave the urea 61 as a voluminous colorless powder;
1
28.55 [3ꢄCACHTNUTRGENNUG(CH3)3], 38.62 (1-C), 49.22 [3ꢄCCAHUTGNTREN(NUGN CH3)3], 64.89
yield: 1.175 g (97%); mp 52–548C. H NMR (400.13 MHz,
˜
(3ꢄCH2), 154.58 ppm (3ꢄC=O); IR (ATR): n=3360, 3320,
2970, 1700, 1600, 1525, 1480, 1445, 1395, 1365, 1310, 1260,
1210, 1090, 1010, 940, 775, 750, 690, 600, 580, 535, 505, 465,
445, 425 cmꢁ1.
CDCl3): d=1.31 [s, 18H, 2ꢄ1’’-(CH3)3], 1.35 [s, 9H, 1’-
(CH3)3], 3.42 (t, 4H, J1,2 =6.2 Hz, 2ꢄ1-H2), 4.09 (t, 4H, J2,1
=
6.2 Hz, 2ꢄ2-H2), 4.81 (br s, 2H, 2ꢄ1’’-NH), 5.18 ppm (br s,
1H, 1’-NH); 13C NMR (100.63 MHz, CDCl3): d=28.97 [2ꢄ
1’’-(CH3)3], 29.55 [1’-(CH3)3], 47.61 (2ꢄC-1), 50.52 (2ꢄC-
1’’), 50.89 (C-1’), 62.37 (2ꢄC-2), 154.75 [2ꢄNHC(=O)O],
˜
157.12 ppm [NHC(=O)N]; IR (film): n=3340, 3055, 2970,
Tetrakis[(N-phenylcarbamoyloxy)methyl]methane
(66)
2935, 1710, 1645, 1535, 1480, 1455, 1395, 1365, 1300, 1270,
1215, 1100, 1065, 1010, 935, 780, 740 cmꢁ1; anal. calcd. for
C19H38N4O5 (402.5): C 56.69, H 9.52, N 13.92; found: C
56.39, H 9.40, N 13.83.
MoO2Cl2ACHTNUTRGNENG(U DMF)2 (3.6 mg, 10 mmol, 0.4 mol% rel. to 63) was
finely ground under a nitrogen atmosphere. Pentaerythritol
(63, 354 mg, 2.60 mmol) and DMF (5.2 mL) were added and
the mixture was heated to 608C, whereupon all components
dissolved. Then, N-phenyl isocyanate (2, 1.24 mL, 1.36 g,
11.4 mmol, 4.4 equiv.) was added at this temperature in one
portion. After 20 min the reaction was quenched by the ad-
dition of H2O (4 mL). The resulting slurry was taken up in
ethyl acetate (60 mL) and HCl(aq) (1N, 30 mL). The aqueous
phase was extracted with ethyl acetate (2ꢄ50 mL). The
combined organic phases were washed with HCl(aq) (1N, 2ꢄ
20 mL), saturated aqueous NaHCO3 solution (30 mL), and
brine (30 mL) and then dried over Na2SO4. Removal of the
solvent under reduced pressure gave the tetracarbamate 66
1,1,1-Tris[(N-phenylcarbamoyloxy)methyl]ethane (64)
MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (1.8 mg, 5.2 mmol, 0.3 mol% rel. to 62) was
finely ground under a nitrogen atmosphere. 1,1,1-Tris(hy-
droxymethyl)ethane (62, 208 mg, 1.73 mmol) was added and
the mixture suspended in (CH2Cl)2 (5.2 mL). N-Phenyl iso-
cyanate (2, 0.62 mL, 0.68 g, 5.7 mmol, 3.3 equiv.) was added
at room temperature and the mixture was heated to reflux
giving a clear solution. After 60 min the reaction mixture
was quenched by the addition of ethyl acetate (60 mL) and
aqueous citric acid (10 wt%, 20 mL). The aqueous phase
was extracted with ethyl acetate (2ꢄ60 mL). The combined
organic phases were washed with aqueous citric acid (10
wt%, 30 mL), saturated aqueous NaHCO3 solution (20 mL),
and brine (20 mL). Drying over Na2SO4 and removal of the
solvent gave the tricarbamate 64 as a colorless solid; yield:
827.1 mg (100%); mp 136–1388C. 1H NMR (400.13 MHz,
DMSO): d=1.08 (s, 3H, 2-H3), 4.12 (s, 6H, 3ꢄCH2), 6.98
(m, 3H, approximately interpretable as tt, Jpara,meta =7.4 Hz,
4Jpara,ortho =1.2 Hz, 3ꢄHpara), AA’BB’ signal centered at dA =
7.25 and dB =7.45 (A: 12H, 6ꢄHmeta, B: 6ꢄHortho), 9.64 ppm
(br s, 3H, 3ꢄNH); 13C NMR (100.63 MHz, DMSO): d=
16.47 (2-C), 30.63 (1-C), 65.58 (3ꢄCH2), 118.21 (br s, 6ꢄ
Cortho), 122.42 (3ꢄCpara), 128.71 (6ꢄCmeta), 138.96 (3ꢄCipso),
1
as a white solid; yield: 1.587 g (100%);. mp 1888C. H NMR
(400.13 MHz, DMSO): d=4.28 (s, 8H, 4ꢄCH2), 6.98 (mc,
4H, approximately interpretable as tt,
Jpara,meta =7.4,
4Jpara,ortho =1.2, 4ꢄHpara), AA’BB’ signal centered at dA =7.26
and dB =7.44 (16H, A: 8ꢄHmeta, B: 8ꢄHortho), 9.68 ppm (br
s, 4H, 4 ꢄ NH); 13C NMR (100.63 MHz, DMSO): d=42.60
(CH2)4], 118.23 (br s, 8ꢄCortho), 122.49
[CACTHNURGTENNUG(CH2)4], 62.48 [CACHUTNGTRENNUGN
(4ꢄCpara), 128.71 (8ꢄCmeta), 138.83 (4ꢄCipso), 153.11 ppm
˜
(4ꢄC=O); IR (ATR): n=3295, 3140, 3065, 2965, 2885, 1700,
1600, 1535, 1500, 1445, 1315, 1225, 1155, 1085, 1065, 930,
905, 850, 755, 725, 690, 505, 430 cmꢁ1; anal. calcd. for
C33H32N4O8 (612.6): C 64.70, H 5.26, N 9.15; found: C 64.68,
H 5.41, N 9.13.
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
19
ÞÞ
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Christian Stock and Reinhard Brꢀckner
FULL PAPERS
[4] a) D. Guꢆnard, F. Guꢆritte-Voegelein, P. Potier, Acc.
Chem. Res. 1993, 26, 160–167; b) K. C. Nicolaou, W.-M.
Dai, R. K. Guy, Angew. Chem. 1994, 106, 38–69;
Angew. Chem. Int. Ed. Engl. 1994, 33, 15–44; c) O. N.
Zefirova, E. V. Nurieva, A. N. Ryzhov, N. V. Zyk, N. S.
Zefirov, Russ. J. Org. Chem. 2005, 41, 315–351.
Tetrakis[(N-tert-butylcarbamoyloxy)methyl]methane
(67)
MoO2Cl2ACHTUNGTRENNUNG(DMF)2 (3.6 mg, 10 mmol, 2.0 mol% rel. to 63) was
finely ground under a nitrogen atmosphere. Pentaerythritol
(63, 68.1 mg, 500 mmol) and DMF (2.0 mL) were added and
the mixture was heated to 608C, whereupon all components
dissolved. Then, N-tert-butyl isocyanate (21, 0.46 mL, 0.40 g,
4.0 mmol, 8.0 equiv.) was added at this temperature in one
portion. After 19 h the reaction was quenched by the addi-
tion of ethyl acetate (75 mL) and aqueous citric acid (10
wt%, 20 mL). The aqueous phase was extracted with ethyl
acetate (3ꢄ60 mL). The combined organic phases were
washed with saturated aqueous NaHCO3 solution saturated
with NaCl (30 mL) and then dried over Na2SO4. Removal of
the solvent under reduced pressure and coevaporation with
heptane (2ꢄ50 mL) gave the tetracarbamate 67 as a 64:34
mixture with its tricarbamate as a white solid; yield:
251.4 mg, (101%); mp 199–2008C. 1H NMR (400.13 MHz,
DMSO; signals of the tetracarbamate 67): d=1.20 (s, 36H,
4ꢄt-Bu), 3.90 (br s, 8H, 4ꢄCH2), 6.85 ppm (br s, 4H, 4ꢄ
[5] J. M. Cassady, K. K. Chan, H. G. Floss, E. Leister,
Chem. Pharm. Bull. 2004, 52, 1–26.
[6] a) G. J. Florence, N. M. Gardner, I. Paterson, Nat.
Prod. Rep. 2008, 25, 342–375; b) A. B. Smith III, B. S.
Freeze, Tetrahedron 2008, 64, 261–298; c) I. Paterson,
G. Florence, Top. Curr. Chem. 2009, 286, 73–119.
[7] For example, Propamocarbꢂ and Carbarylꢂ; cf.
Rçmpp Online, Version 3.1, Georg Thieme Verlag,
Stuttgart 2008.
ꢁ ꢄ
[8] a) L. Rossi, Four Carbon-Heteroatom Bonds: X C X,
X=C=X, X2C=X, CX4, in: Science of Synthesis –
Houben-Weyl Methods of Organic Chemistry, Vol. 18
(Ed.: J. G. Knight), Georg Thieme Verlag, Stuttgart,
New York, 2005, pp 461–648; b) D. Chaturvedi, N.
Mishra, V. Mishra, Curr. Org. Synth. 2007, 4, 308–320.
[9] A. L. Win-Mason, E. M. Dangerfield, P. C. Tyler, B. L.
Stocker, M. S. M. Timmer, Eur. J. Org. Chem. 2011,
4008–4014.
1
NH). H NMR (400.13 MHz, DMSO; signals of the respec-
tive tricarbamate 92): d=1.20 (s, 27H, 3ꢄt-Bu), 3.39 (d, 2H,
J
CH2OH,OH =5.2 Hz, CH2OH), 3.87 [br s, 6H, 3ꢄCH2OC(=
O)N], 6.79 ppm (br s, 3H, 3ꢄNH); 13C NMR (100.63 MHz,
DMSO): d=28.52 [4ꢄC(CH3)3], 42.05 [C(CH2)4], 49.22 [4ꢄ
(CH3)3], 61.86 [C(CH2)4], 154.39 ppm (4ꢄC=O); IR (film):
[10] E. Borsini, G. Broggini, A. Fasana, S. Galli, M. Khan-
saa, U. Piarulli, M. Rigamonti, Adv. Synth. Catal. 2011,
353, 985–994.
A
ACHTUNGTRENNUNG
C
N
ACHTUNGTRENNUNG
˜
n=3380, 2970, 2935, 2360, 1715, 1525, 1460, 1395, 1365,
1265, 1210, 1095, 995, 975, 940, 775, 755, 670 cmꢁ1; MS
(ESI): m/z (%)=578 (15), 555 (M+Na+, 100), 457 (tricarba-
mate+Na+, 9), 335 (6).
[11] P. G. M. Wuts, T. W. Greene, Greeneꢁs Protective
Groups in Organic Synthesis, 4th edn., John Wiley and
Sons, Inc., Hoboken, New Jersey, 2007, pp 706–771.
[12] a) M. Kosugi, K. Yano, M. Chiba, T. Migita, Chem.
Lett. 1977, 801–804; b) J. Lessard, M. Mondon, D. Tou-
chard, Can. J. Chem. 1981, 59, 431–450; c) J. J. C.
Dockx, A. G. M. de Knaep, R. W. H. Albert, Synthesis
1982, 511–513; d) C. G. Francisco, A. J. Herrera, E.
Suꢇrez, J. Org. Chem. 2003, 68, 1012–1017; e) K. Chen,
J. M. Richter, P. S. Baran, J. Am. Chem. Soc. 2008, 130,
7247–7249.
Acknowledgements
C. S. was supported by a fellowship of the IRTG 1038 “Cata-
lysts and Catalytic Reactions for Synthesis” of the Deutsche
Forschungsgemeinschaft.
[13] a) V. Snieckus, Chem. Rev. 1990, 90, 879–933; b) D.
Hoppe, Synthesis 2009, 43–55.
[14] In heterocycles with diastereotopic faces: a) F. Glorius,
N. Spielkamp, S. Holle, R. Goddard, C. W. Lehmann,
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[17] Preliminary comunication: C. Stock, R. Brꢀckner, Syn-
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20
asc.wiley-vch.de
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
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Mild and High-Yielding Molybdenum(VI) Dichloride Dioxide-Catalyzed Formation
[18] Review on DMAP catalysis: G. Hçfle, W. Steglich, H.
Vorbrꢀggen, Angew. Chem. 1978, 90, 602–615; Angew.
Chem. Int. Ed. Engl. 1978, 17, 569–583.
[19] Representative examples for carbamate formations in
the presence of DMAP: a) B. Elman, C. Moberg, Tetra-
hedron 1986, 42, 223–228; b) J. F. Cameron, C. G. Will-
son, J. M. J. Frꢆchet, J. Chem. Soc. Perkin Trans. 1 1997,
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Ma, Org. Lett. 2005, 7, 847–849.
[20] W. C. Still, M. Kahn, A. Mitra, J. Org. Chem. 1978, 43,
2923–2925.
[21] C.-T. Chen, J.-H. Kuo, V. D. Pawar, Y. S. Munot, S.-S.
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1188–1197.
[22] This addition product is depicted as compound 85 in
Scheme 8>.
[23] Review of organic synthesis applications of MoO2Cl2
ACHTUNGTRENNUNG(DMF)2: K. Jeyakumar, D. K. Chand, J. Chem. Sci.
2009, 121, 111–123.
[24] Preparation of MoO2Cl2ACHTNUGTRNE(UNG DMF)2 from Na2MoO4·2H2O,
[28] Accordingly, it is mere speculation whether during car-
bamate formation from tert-butyl isocyanate (21) and
diols 48 or 49 the rate-determining step is the activa-
tion of 21 by the molybdenum complex (cf. the mecha-
nistic proposal of Scheme 8).
[29] Compound 92 is depicted and described only in the Ex-
perimental Section.
[30] According to Volpin et al. three oxorhenium complexes
(R3P)2Re(=O)Cl3 and N-phenyl isocyanate (2) gave the
respective imido complexes (R3P)2ReACHTNUTRGNE(NUG =NPh)Cl3 and
CO2. In addition the evolution of CO2 was observed
upon the addition of N-phenyl isocyanate (2) to oxo
complexes of other transition metals including molyb-
denum (e.g., CpMoOCl2), see: I. S. Kolomnikov, Y. D.
Koreshkov, T. S. Lobeeva, M. E. Volpin, J. Chem. Soc.
Chem. Commun. 1970, 1432.
[31] WOCl4 and N-phenyl isocyanate furnished the imido
tungsten complex shown below in 86% yield, see: D. C.
Bradley, M. B. Hursthouse, K. M. A. Malik, A. J. Niel-
son, R. L. Short, J. Chem. Soc. Dalton Trans. 1983,
2651–2656.
conc. HCl and DMF: R. Sanz, J. Escribano, R. Aguado,
M. R. Pedrosa, F. F. Arnꢇiz, Synthesis 2004, 1629–1632.
[25] MoO2Cl2ACHTUNGTRENNUNG(DMF)2 is water-soluble and can be removed
by simple aqueous work-up under neutral conditions.
[26] The mass balance of any carbamate synthesis stems
from weighing the reactants and the product in flasks
or from adding liquid substrates on scales ꢂ230 mL by
measuring their volume with an appropriate syringe.
The inherent error limit of our scales, error propaga-
tion and error enhancement due to subtracting weights
from one another, the sensitivity of small-scale work
(down to 68 mg and 230 mL, respectively) to these
kinds of errors, and an awareness for non-zero detec-
tion limits of 1H NMR spectroscopy for unreacted
starting materials or side-products caused a number of
reactions to deliver yields which were calculated to be
ꢂ100%. We refer to such cases in the Tables, Schemes,
and text by designating such yields as “quantitative”.
However, this designation must not be overvalued as
pointed out, see: M. Wernerova, T. Hudlicky, Synlett
2010, 2701–2707 and T. Lairs, Org. Process Res. Dev.
2011, 15, 305–305.
[32] From the reaction of the dinuclear oxorhenium com-
plex (Cp*ReO2)2 with N-phenyl isocyanate 58% of an
undecarboxylated mononuclear rhenaoxazetidinone
was isolated, see: U. Kꢀsthardt, W. A. Herrmann, M. L.
Ziegler, T. Zahn, B. Nuber, J. Organomet. Chem. 1986,
311, 163–175. It was characterized by 1H NMR,
13C NMR, and IR spectroscopy as well as bei MS, com-
bustion analysis, and X-ray analysis:
[27] Carbamates 6–9, 28, 29, and 33 as well as the dicarba-
mates 42–47 and 51–56, the oligocarbamates 64–67, and
the diethanolamine-derived products 57, 58, 60, and 61
were prepared for the first time in our study. Prepara-
tions of the N-phenyl carbamates 22–27 from their re-
spective underlying alcohol/isocyanate pairs are already
described in the literature. The particular references
are given within the experimental section. The O-
menthyl carbamates 11 and 30–32 as well as the bis(e-
thylcarbamates) 39–41 have already been prepared, but
according to the literature there seems to be no prior
preparation from the respective underlying isocyanate
pairs. These references are also cited in the experimen-
tal part. All reactions yielded analytically pure com-
pounds after simple aqueous work-up as judged by
1H NMR (400 MHz) and correct combustion analysis
data (i.e., values for mass% H and mass% C within
ꢅ0.30% intervals around the caclulated values). They
were never purified by chromatography or recrystalli-
zation.
[33] The reaction of VOCl3 with 1-adamantyl isocyanate fol-
lowed by complexation with DME led to an imido va-
nadium complex in 78% yield, see: F. Montilla, A.
Pastor, A. Monge, E. Gutiꢆrrez-Puebla, A. Galindo, J.
Chem. Soc. Dalton Trans. 1999, 2893–2896.
[34] The following conversion of an oxo-substituted into an
imino-substituted titanium phthalocyanine complex,
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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21
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Christian Stock and Reinhard Brꢀckner
FULL PAPERS
which was accompanied by the release of CO2 was ef-
fected by N-2,6-diisopropylphenyl isocyanate, see: W.
Darwish, E. Seikel, R. Kꢁsmarker, K. Harms, J. Sunder-
meyer, Dalton Trans. 2011, 40, 1787–1794.
[43] T. A. Coffey, G. D. Forster, G. Hogarth, J. Chem. Soc.
Dalton Trans. 1995, 2337–2349.
[44] In complex 78 the Mo atom is pentacoordinated where-
as complexes 71, 74, 76, 80, and 82 contain a hexacoor-
dinated Mo atom. The deviation might be due to the
severe steric crowding caused by the N-tert-butyl group
and the large O-aryl moieties.
[45] According to the literature there seem to be no prior
preparations of carbamates 11, 30, and 32 from the un-
derlying alcohol/isocyanate pairs. An alternative access
was described, seeI. Meyer, H. Oertling, N. Hillebrand,
C. Gçmann, R. Brodhage, WO Patent 2010/089421A2,
2010, but no yields were reported.
[46] Carbamate 22 was prepared in 65% yield from the un-
derlying alcohol/isocyanate pair, see: G. G. Muccioli, G.
Labar, D. M. Lambert, ChemBioChem 2008, 9, 2704–
2710.
[47] The preparation of carbamate 23 from the underlying
alcohol/isocyanate pair was described, see: R. Seemay-
er, J. Liang, WO Patent 2004/037827A1, 2004, but with-
out isolation or characterization of the product.
[48] Carbamate 24 was prepared in 80–90% yield from the
underlying alcohol/isocyanate pair, see: Y. Tamaru, M.
Kimura, S. Tanaka, S. Kure, Z.-i. Yoshida, Bull. Chem.
Soc. Jpn. 1994, 67, 2838–2849.
[35] Such a compound can be – and was (ref.[32]) – referred
to as an (N,O)-carbamidato-complex.
[36] a) P. Jernakoff, G. L. Geoffroy, A. L. Rheingold, S. J.
Geib, J. Chem. Soc. Chem. Commun. 1987, 1610–1611;
b) R. S. Pilato, C. E. Housmekerides, P. Jernakoff. D.
Rubin, G. L. Geoffroy, Organometallics 1990, 9, 2333–
2341.
[37] The opposite process was described; however, the
imido-molybdenum complex shown below picks up
carbon dioxide to form the corresponding molybdaoxa-
zetidinone in 91% yield, see: Z. J. Tonzetich, R. R.
Schrock, P. Mꢀller, Organometallics 2006, 25, 4301–
4306.
[49] Carbamate 25 was prepared in 85% yield from the un-
derlying alcohol/isocyanate pair, see: K. B. Wiberg, Y.-
g. Wang, S. J. Miller, A. L. A. Puchlopek, W. F. Bailey,
J. D. Fair, J. Org. Chem. 2009, 74, 3659–3664.
[50] Carbamate 26 was prepared in 82% yield from the un-
derlying alcohol/isocyanate pair, see: T. Steinke, B. K.
Shaw, H. Jong, B. O. Patrick, M. D. Fryzuk, Organome-
tallics 2009, 28, 2830–2836.
[51] Carbamate 27 has already been prepared in 67% yield
from the underlying alcohol/isocyanate pair, see: R.
Delatouche, A. Lesage, F. Collette, V. Hꢆroguez, P.
Bertrand, Aust. J. Chem. 2011, 64, 166–173.
[52] According to the literature there seems to be no prior
preparation of carbamate 31 from the underlying alco-
hol/isocyanate pair. An alternative access in 80% yield
was described, though, see: R. Martꢈnez, D. J. Ramꢉn,
M. Yus, Adv. Synth. Catal. 2008, 350, 1235–1240.
[53] According to the literature there seem to be no prior
preparations of dicarbamates 39 and 40 from the un-
derlying alcohol/diisocyanate pairs. An alternative
access in 96 and 94% yields, respectively, was de-
scribed, though, see: E. Reixach, N. Bonet, F. X. Rius-
Ruiz, S. Wershofen, A. Vidal-Ferran, Ind. Eng. Chem.
Res. 2010, 49, 6362–6366.
[38] D. Ehrenfeld, J. Kress, B. D. Moore, J. A. Osborn, G.
Schoettel, J. Chem. Soc. Chem. Commun. 1987, 129–
131.
[39] A. W. Holland, R. G. Bergman, J. Am. Chem. Soc.
2002, 124, 9010–9011.
[54] According to the literature there seems to be no prior
preparation of dicarbamate 41 from the underlying al-
cohol/diisocyanate pair. An alternative access without
a given yield was described, though, see: T. W. Leung,
B. D. Dombek, J. Chem. Soc. Chem. Commun. 1992,
205–206.
[40] F. J. de La Mata, J. W. Ziller, J. Organomet. Chem.
1998, 564, 85–92.
[41] W. B. Cross, J. C. Anderson, C. Wilson, A. J. Blake,
Inorg. Chem. 2006, 45, 4556–4561.
[42] A. Lehtonen, H. Balcar, R. Sillanpꢁꢁ, J. Organomet.
Chem. 2009, 694, 649–654.
22
asc.wiley-vch.de
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

FULL PAPERS
Mild and High-Yielding Molybdenum(VI) Dichloride
Dioxide-Catalyzed Formation of Mono-, Di-, Tri-, and
Tetracarbamates from Alcohols and Aromatic or Aliphatic
Isocyanates
23
Adv. Synth. Catal. 2012, 354, 1 – 23
Christian Stock, Reinhard Brꢀckner*
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
23
ÞÞ
These are not the final page numbers!