Synthesis of oxazolidin-2-ones and imidazolidin-2-ones directly from 1,3-diols or 3-amino alcohols using iodobenzene dichloride and sodium azide

Article abstract of DOI:10.1002/adsc.201300982

A general and efficient method for the synthesis of oxazolidin-2-ones and imidazolidin-2-ones directly from 1,3-diols and 3-amino alcohols has been developed using the same reagent combination of iodobenzene dichloride (PhICl₂) and sodium azide (NaN₃).

Full text of DOI:10.1002/adsc.201300982

UPDATES
DOI: 10.1002/adsc.201300982
Synthesis of Oxazolidin-2-ones and Imidazolidin-2-ones
Directly from 1,3-Diols or 3-Amino Alcohols using Iodobenzene
Dichloride and Sodium Azide
Tian He,a Wen-Chao Gao,a Wei-Kun Wang,a and Chi Zhanga,*
a
State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and
Engineering (Tianjin), The Research Institute of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071,
Peopleꢀs Republic of China
Fax : (+86)-22-2350-3627; e-mail: zhangchi@nankai.edu.cn
Received: November 5, 2013; Revised: December 13, 2013; Published online: March 12, 2014
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201300982.
Abstract: A general and efficient method for the
synthesis of oxazolidin-2-ones and imidazolidin-2-
ones directly from 1,3-diols and 3-amino alcohols
has been developed using the same reagent combi-
nation of iodobenzene dichloride (PhICl2) and
sodium azide (NaN3).
particular, Evans auxiliaries, bearing oxazolidin-2-one
moiety, are extensively applied in asymmetric alkyla-
tion,[5] aldol reaction,[6] Diels–Alder reaction,[7] and
asymmetric fluorination reaction.[8] Furthermore, oxa-
zolidin-2-ones and imidazolidin-2-ones can be em-
ployed as synthetic intermediates for the preparation
of 2-amino alcohols and 1,2-diamines.[9] Accordingly,
various synthetic methods have been developed for
their syntheses.[10] Conventionally, oxazolidin-2-ones
and imidazolidin-2-ones are prepared respectively
from 2-amino alcohols and 1,2-diamines with carbonyl
source compounds such as phosgene,[11] phosgene de-
rivatives,[12] carbon monoxide,[13] and carbon diox-
Keywords: imidazolidin-2-ones; iodobenzene di-
chloride; oxazolidin-2-ones; sodium azide
Oxazolidin-2-one and imidazolidin-2-one motifs are ide.[14] However, phosgene and carbon monoxide are
common structural units in many natural products,[1] highly toxic compounds and they are difficult to
pharmaceuticals,[2] and biologically active com- handle in the laboratory; using carbon dioxide as the
pounds,[3] as exemplified by (ꢀ)-agelastatin A,[1a] carbonyl source always requires harsh reaction condi-
linezolid,[2b] and KVI-020[3a] (Figure 1). Oxazolidin-2- tions, i.e., high temperature and/or high pressure. Al-
ones and imidazolidin-2-ones can also serve as chiral ternative synthetic routes with aziridines,[15] epox-
auxiliaries in a number of asymmetric reactions;[4] in ides,[16] and olefins[17] as the starting materials have
also been developed. Although the above mentioned
methods focus on the intermolecular reactions to
afford oxazolidin-2-ones and imidazolidin-2-ones, the
intramolecular cyclization approaches to synthesize
these two heterocyclic compounds have also been de-
veloped, including palladium(II)-catalyzed diamina-
tion of alkenes to synthesize imidazolidin-2-ones,[18]
ꢀ
transition metal-catalyzed amidation of saturated C
H bonds for the conversion of O-alkyl carbamates to
oxazolidin-2-ones,[19] the Hofmann rearrangement of
3-hydroxy or 3-amino amides,[20a,b] and Curtius rear-
rangement of b-functionalized carboxylic acids pro-
moted by polymer-supported diphenylphosphoryl
azide (PS-DPPA).[20c] Among the metal-free strat-
egies,[20] the methods involving Hofmann rearrange-
ment had a narrow substrate scope and offered only
one type of heterocycle; although the Curtius rear-
Figure 1. Selected molecules bearing oxazolidin-2-one and
imidazolidin-2-one moieties.
rangement of b-functionalized carboxylic acids could
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Tian He et al.
realize the synthesis of both oxazolidin-2-ones and creased to 89% (entry 3). Further reducing the
imidazolidin-2-ones, the multistep synthesis of PS- amount of PhICl2 and NaN3 resulted in a decreased
DPPA has limited its synthetic application.[20e] More- yield of 2a (entry 4). Consequently, the optimized re-
over, it seems inevitable that all these intramolecular action system for the efficient synthesis of oxazolidin-
methods need the carbonyl group to be embedded in 2-one 2a from 1,3-diol 1a was composed of 4.0 equiva-
the starting materials. Therefore, it is still highly desir- lents of PhICl2, 8.0 equivalents of NaN3, and ethyl
able to explore a general intramolecular route to syn- acetate as the solvent, with stage-wise reaction tem-
thesize oxazolidin-2-ones and imidazolidin-2-ones perature modulation.
from the low oxidation state functionality such as a hy-
droxy group via facile oxidative manipulation using a series of 1,3-diols was subjected to the optimal reac-
readily available oxidants. tion conditions and the results are summarized in
To test the generality and scope of this method,
In our previous work, it has been reported that the Table 2. 3-Phenylbutane-1,3-diol (1b) and 1,1-diphe-
combined reagent system of PhICl2-NaN3 could be nylpropane-1,3-diol (1c), both bearing the phenyl
used for the efficient transformation of primary alco- ring, were smoothly converted into 2b and 2c in 83%
hols to the corresponding carbamoyl azides in and 74% yields, respectively (Table 2, entries 2 and
CH3CN;[21] subsequently, the same reagent combina- 3). It was worth noting that 2a and 2c have been used
tion has also been applied to the synthesis of substi- for the preparation of N-phosphoryloxazolidin-2-ones,
tuted ureas directly from primary alcohols and amines which were effective phosphorylating agents for a vari-
via the key intermediate carbamoyl azides in ety of alcohols.[23]
EtOAc.[22] Herein, as part of our continuing research
For 1,3-diols having alkyl and phenyl substituents,
on new synthetic applications of the PhICl2-NaN3 such as 1d, 1e, and 1f, the reaction also worked well,
system, we disclose a novel and general intramolecu- affording 2d, 2e, and 2f in good to excellent yield (en-
lar method for the synthesis of oxazolidin-2-ones and tries 4–6). For the substrates like 1g and 1h, whose
imidazolidin-2-ones via oxidation of 1,3-diols and 3- tertiary hydroxy group and the hydroxymethyl group
amino alcohols, respectively. To the best of our were joined to the vicinal carbon on the cyclic ring,
knowledge, as an intramolecular cyclzation protocol, the desired fused-oxazolidin-2-one 2g and 2h were ob-
this is the first example to synthesize oxazolidin-2- tained in good yield (entries 7 and 8). As for the sub-
ones and imidazolidin-2-ones from the low oxidation strates whose tertiary hydroxy group and hydroxyeth-
state substrates without embedded carbonyl groups.
yl group were attached at the same ring carbon, such
The initial study was carried out with 3-methylbu- as 1i, 1j, and 1k, the corresponding spiro-oxazolidin-2-
tane-1,3-diol (1a) as the model substrate under the ones 2i–k were produced in 83%, 78%, and 72%
standard conditions (5 equiv. PhICl2/10 equiv. NaN3) yields, respectively (entries 9–11). After the successful
for the effective transformation of primary alcohols to construction of oxazolidin-2-ones from 1,3-diols with
carbamoyl azides in ethyl acetate, which were the key a tertiary hydroxy group, 4,4-dimethylpentane-1,3-diol
intermediates for the synthesis of substituted ureas in (1l) containing a secondary hydroxy group adjacent to
our previous work.[22] Pleasingly, 5,5-dimethyloxazoli- a bulky t-Bu group was tested under the optimal reac-
din-2-one (2a) was obtained in 86% yield (Table 1, tion conditions, however, the desired 5-tert-butyloxa-
entry 1). Reducing the amount of NaN3 alone resulted zolidin-2-one (2l) was produced only in 10% yield,
in a dramatically decreased yield of 2a (entry 2). and the major product was 1-hydroxy-4,4-dimethyl-
When the amounts of PhICl2 and NaN3 were reduced pentan-3-one due to the preferential oxidation of sec-
proportionally, the yield of 2a was however slightly in- ondary alcohols over primary ones using the reagent
combination of PhICl2-NaN3 (entry 12).[21]
After the successful construction of oxazolidin-2-
ones from 1,3-diols, we surmised that imidazolidin-2-
Table 1. Optimization of reagent amount in the synthesis of
oxazolidin-2-one 2a.[a]
ones could also be obtained following the same strat-
egy if we changed the nucleophilic functionality em-
bedded in the substrate from a hydroxy group to an
amino group. Therefore, we tested this hypothesis
using PhICl2 (4.0 equiv.) and NaN3 (8.0 equiv.) with
N-(3-hydroxypropyl)-4-methylbenzenesulfonamide
(3a) as the model substrate, as expected, 1-tosylimida-
zolidin-2-one (4a) was formed in 63% yield (Table 3,
entry 1). Results of the screening study of the amount
of employed reagents indicated that 5.0 equivalents of
PhICl2 and 10.0 equivalents of NaN3 were best for
this transformation (entries 2 and 3). Next, several
other commonly used N-protecting groups, such as 4-
Entry
PhICl2 (equiv.)
NaN3 (equiv.)
Yield [%][b]
1
2
3
4
5.0
5.0
4.0
3.0
10.0
5.0
8.0
6.0
86
51
89
78
[a]
The reactions were carried out using 1 mmol of 1a.
Isolated yield.
[b]
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UPDATES
Synthesis of Oxazolidin-2-ones and Imidazolidin-2-ones
Table 2. Intramolecular cyclization of 1,3-diols to oxazolidin-
Table 3. Optimization of reagent amount and the screening
of N-protecting groups in the synthesis of imidazolidin-2-
ones.[a]
2-ones with the PhICl2-NaN3 system.[a]
Entry PG
PhICl2 (equiv.) NaN3 (equiv.) Yield [%][b]
1
2
3
4
Ts
Ts
Ts
p-Ns
Ms
Ac
Boc
4.0
5.0
6.0
5.0
5.0
5.0
5.0
8.0
63
76
75
73
31
0
10.0
12.0
10.0
10.0
10.0
10.0
10.0
5
6
7[c]
8[d]
0
0
CF3CO 5.0
[a]
[b]
[c]
The reactions were run with 0.5 mmol of substrates.
Isolated yield.
tert-Butyl 2-(azidocarbonylamino)ethylcarbamate was ob-
tained in 42% yield.
[2-(2,2,2-Trifluoroacetamido)ethyl]carbamoyl azide was
obtained in 79% yield.
[d]
them showed a superior result compared with the
para-toluenesulfonyl (Ts) group (entries 4–8 vs.
entry 2). When the N-protecting group was an acetyl
group, a complex reaction mixture was obtained and
no hetero-annulation product was detected. As for N-
Boc and N-CF3CO protected 3-amino alcohols, no de-
sired imidazolidin-2-ones were detected, and the main
products were tert-butyl 2-(azidocarbonylamino)ethyl-
carbamate and [2-(2,2,2-trifluoroacetamido)ethyl]car-
bamoyl azide, respectively, which were produced via
the addition of hydrazoic acid generated in situ to the
corresponding isocyanates formed from the conver-
sion of the primary alcohol functionality of 3-amino
alcohols.[22]
With the optimized reaction conditions in hand,
a series of N-Ts protected 3-amino alcohols was
tested and the results are summarized in Table 4. For
substrates bearing alkyl substituents such as methyl,
ethyl, and tert-butyl groups, the reaction also worked
as well as with 3a, affording the desired imidazolidin-
2-ones especially for multi-substituted ones in good to
excellent yields (Table 4, entries 1–7). It should be no-
ticed that there was no deleterious influence on the
imidazolidin-2-one yield even though a bulky group
like tert-butyl group was close to the tosylamido
group (entry 4 vs. entry 1). Two substrates bearing
ester and amide functional groups were well tolerated
under the present reaction conditions as indicated by
the successful transformation of 3h and 3i to the prod-
[a]
The reaction was run with 1 mmol of 1,3-diol com-
pounds.
Isolated yield.
5.0 equivalents of PhICl2 and 10.0 equivalents of NaN3
were used.
The data in the parentheses are the chemical yields
based on the recovered 1,3-diol.
[b]
[c]
[d]
[e]
45% of 1-hydroxy-4,4-dimethylpentan-3-one was ob-
tained.
nitrobenzenesulfonyl (p-Ns), methanesulfonyl (Ms), ucts 4h and 4i (entries 8 and 9). As for the substrates
acetyl (Ac), tert-butoxycarbonyl (Boc), and trifluoro- whose tosylamido group and the hydroxymethyl
ACHTUNGTRENNUNGacetyl (CF3CO) were also checked, however, none of group were joined to the vicinal carbon on the ring,
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Tian He et al.
Table 4. Intramolecular cyclization of 3-amino alcohols to
imidazolidin-2-ones with the PhICl2-NaN3 system.[a]
Scheme 1. Proposed mechanism.
on the ring were tested, the reactions also worked
well, yielding the desired spiro-imidazolidin-2-one 4l
and 4m in, respectively, 78% and 71% yields (en-
tries 12 and 13).
On the basis of our previous works disclosing that
primary alcohols can be converted into the corre-
sponding carbamoyl azides via multiple steps includ-
ing alcohols!aldehydes!acyl azides!isocyanates!
carbamoyl azides,[21,22] a step-wise mechanism for the
transformation of 1,3-diols and N-Ts protected 3-
amino alcohols to oxazolidin-2-ones and imidazolidin-
2-ones was proposed (Scheme 1). The primary alcohol
of the starting 1,3-diols or N-Ts protected 3-amino al-
cohols was transformed into the corresponding isocya-
nate functionality via the same pathway as the above
mentioned, then an intramolecular cyclization reac-
tion occurred due to the inherent nucleophilic proper-
ty of the hydroxyl- and tosyl-protected amino groups
to generate the product oxazolidin-2-ones and imida-
zolidin-2-ones, respectively.[24]
In summary, we have presented here a general,
metal-free, and efficient method for the facile access
to oxazolidin-2-ones and imidazolidin-2-ones directly
from 1,3-diols and 3-amino alcohols with the com-
bined reagent PhICl2-NaN3. The ready availability of
[25]
PhICl2
which was quickly and quantitatively pre-
pared from iodobenzene using bleach in acidic aque-
ous media and low-cost nitrogen source compound
NaN3, the simple work-up, and the broad substrate
generality make the present protocol an attractive
way to synthesize oxazolidin-2-ones and imidazolidin-
2-ones.
[a]
The reactions were run with 0.5 mmol of substrates.
Isolated yield.
The reaction was run on a 0.15 mmol scale.
The reaction was run on a 0.1 mmol scale.
[b]
[c]
[d]
Experimental Section
Caution! Although no explosion occurred in our laboratory
during our investigation of the applications of the com-
bined reagent system of PhICl2-NaN3, azido compounds are
hazardous and may explode when heated. A safety shield,
their corresponding fused imidazolidin-2-ones 4j and
4k were produced in good yields (entries 10 and 11).
When the substrates whose tosylamido group and hy-
droxymethyl group were attached at the same carbon gloves, and eye protection are highly recommended.
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UPDATES
Synthesis of Oxazolidin-2-ones and Imidazolidin-2-ones
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Typical Procedure for the Synthesis of Oxazolidin-2-
ones
To a solution of 1a (104 mg, 1 mmol) in EtOAc (10 mL)
were added PhICl2 (1.1 g, 4 mmol) and NaN3 (520 mg,
8 mmol) under an N2 atmosphere at 08C, and the reaction
mixture was stirred at 08C for 4 h. Subsequently, the reac-
tion mixture was heated to 808C for 8 h. Then, the reaction
mixture was cooled to room temperature and diluted with
EtOAc (50 mL). The resulting mixture was quenched with
saturated Na2S2O3 (15 mL) and extracted with EtOAc (2ꢂ
20 mL). The combined organic layer was washed with brine
(20 mL), dried over anhydrous Na2SO4, and concentrated
under reduced pressure to afford the crude product. Pure 2a
was obtained in 89% yield after the flash column chroma-
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Typical Procedure for the Synthesis of imidazolidin-2-
ones
To a solution of 3a (115 mg, 0.5 mmol) in EtOAc (8 mL)
were added PhICl2 (688 mg, 2.5 mmol) and NaN3 (325 mg,
5 mmol) under an N2 atmosphere at 08C, and the reaction
mixture was stirred at 08C for 4 h. Subsequently, the reac-
tion mixture was heated to 808C for 8 h. Then, the reaction
mixture was cooled to room temperature and diluted with
EtOAc (50 mL). The resulting mixture was quenched with
saturated Na2S2O3 (15 mL), and extracted with EtOAc (2ꢂ
20 mL). The combined organic layer was washed with brine
(20 mL), dried over anhydrous Na2SO4, and concentrated to
afford the crude product. Pure 4a was obtained in 76% yield
after the flash column chromatography.
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Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (21172110 and 21121002).
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