Catalytic Dealkylative Synthesis of Cyclic Carbamates and Ureas via Hydrogen Atom Transfer and Radical-Polar Crossover

Article abstract of DOI:10.1021/acs.orglett.0c01872

Guided by the transition-metal hydrogen atom transfer and radical-polar crossover concepts, we developed a functional-group-tolerant and scalable method for the synthesis of cyclic carbamates and ureas, which are found in the structures of bioactive compo

Full text of DOI:10.1021/acs.orglett.0c01872

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Letter
Catalytic Dealkylative Synthesis of Cyclic Carbamates and Ureas via
Hydrogen Atom Transfer and Radical-Polar Crossover
Takuya Nagai, Nao Mimata, Yoshihiro Terada, Chikayoshi Sebe, and Hiroki Shigehisa*
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ABSTRACT: Guided by the transition-metal hydrogen atom
transfer and radical-polar crossover concepts, we developed a
functional-group-tolerant and scalable method for the synthesis of
cyclic carbamates and ureas, which are found in the structures of
bioactive compounds. This method provides not only a common
five-membered ring but also six-to-eight-membered ring products.
The reaction proceeds through the intramolecular displacement of
an alkylcobalt(IV) intermediate and dealkylation by 2,4,6-collidine;
the activation energies of these steps were calculated by DFT.
HAT/RPC mechanism prompted us to design further
uch effort has been devoted in modern synthetic
Morganic chemistry to the development of diverse cyclization reactions that involve poorly nucleophilic species.
Herein, we report the dealkylative cyclizations of alkenyl
carbamates and alkenyl isoureas to afford cyclic carbamates
and cyclic ureas, respectively (Scheme 1C). Cyclic
carbamates and ureas are important structural motifs found
in pharmaceuticals and bioactive agents, such as linezolid
(antibiotic active against VRE and MRSA),9 efavirenz (anti-
HIV drug),10 biotin (cofactor),11 and aquiledine (natural
product).12 This observation encouraged synthetic chemists
to develop various preparative methods for cyclic carba-
mates13 and cyclic ureas.14 However, to the best of our
knowledge, the substrate scope of most reactions is limited to
only common five- and six-membered rings, and examples of
medium ring formation are rather rare.13g,14g On the other
hand, the method described here provides five- to eight-
membered ring compounds.
We commenced by determining an appropriate carbamate
structure using previously developed reaction conditions:
cobalt catalyst C1, N-fluoro-2,4,6-collidinium trifluorometha-
nesulfonate (3), and 1,1,3,3-tetramethyldisiloxane in benzotri-
fluoride at room temperature (Scheme 2). Although the
desired oxazolidinone 2 was obtained from all substrates 1a−
1c, we found that tert-butyl carbamate 1c gave the best
results. It should be noted that the methyl ester gave a better
methods for hydrofunctionalizing alkenes through transition-
metal hydrogen-atom-transfer (TM-HAT) processes.1
A
transition metal hydride generated in situ from a catalyst
and a hydrogen source reacts with the alkene unit to
chemoselectively generate a carbon-centered radical that then
becomes involved in diverse transformations (Scheme 1A).2
Recently, this mechanism has been shown to operate in
conjunction with other transition-metal catalysis mechanisms,
thereby expanding the scope of the transformation.3
Our group has independently shown that the addition of
an N-fluorocollidinium salt to a commonly used cobalt−Schiff
base catalyst and a silane facilitates radical-polar crossover
(RPC) to generate a cationic intermediate. To date, we have
disclosed that oxygen,4 nitrogen,5 carbon,6 and sulfur7
nucleophiles react with these cationic species in TM-HAT
chemistry. Among them, the formation of a lactone from an
alkenyl ester is a profound example for us (Scheme 1B).4b
Importantly, Shenvi investigated the mechanism of their
bimetallic coupling reaction in the presence of an N-
fluorocollidinium salt and suggested the involvement of an
alkylcobalt(IV) intermediate.3b In light of Shenvi and related
reports2u,w,7,8 for the lactone formation, it is plausible that the
sp2 oxygen atom of the carbonyl group attacks the reactive
cationic carbon of the alkylcobalt(IV) intermediate to release
a cobalt(II) complex, after which removal of the methyl
group by 2,4,6-collidine led to the lactone. Indeed, we
computed the activation energies for the steps involving TS-a
and TS-b to be only 11.0 and 14.1 kcal/mol, which suggests
that these two steps are possible. With the aim of expanding
the substrate scope, the promising reactivity of the TM-
Received: June 4, 2020
https://dx.doi.org/10.1021/acs.orglett.0c01872
© XXXX American Chemical Society
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A

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Scheme 1. TM-HAT and RPC Mechanisms
a
Scheme 2. Initial Attempt of Oxazolidine Synthesis
a
The reactions of 1a−1c (0.20 mmol) were performed in the presence of C1 (3 mol %), 3 (2.0 equiv), and 1,1,3,3-tetramethyldisiloxane (2.0
equiv) in benzotrifluoride (2.0 mL) at room temperature for 18 h under argon. Isolated yields are shown. DFT calculations were performed for the
synthesis of 5 to reduce calculational costs.
yield than the corresponding tert-butyl ester in the previously
reported dealkylative cyclization that affords lactones.4b We
also observed coproducts 4 in 98% yield (based on 3).
Therefore, the deprotonation of the tert-butyl group by 2,4,6-
collidine occurs after cyclization of the alkylcobalt(IV)
intermediate. The activation energies for the steps involving
TS-c and TS-d were calculated to be only 12.6 and 7.2 kcal/
mol (without the OMe group to reduce calculational costs),
which suggests that the mechanism shown in Scheme 2 is
feasible.
Encouraged by this result, we next examined the alkenyl
carbamate scope for the formation of oxazolidinones (Scheme
3). Starting materials bearing hydrogen (i.e., 5) or a methyl
group (i.e., 6) in the p-position of the aniline unit gave good
yields of the desired products. On the other hand, the
introduction of electron-withdrawing chloro, fluoro, and
trifluoromethyl groups (7−9) led to significantly lower yields
and the recovery of the alkenyl tert-butyl carbamate.
Fortunately, we solved this problem by replacing the
carbamate unit with a methyl group. Clearly, these results
contrast with those from the reaction that produces 2 with
the electron-donating methoxy group. These aryl substituents
would affect the rate of the intramolecular nucleophilic
displacement and subsequent dealkylation, although their
exact roles are not immediately clear. We also examined the
functional group tolerance of this reaction using substrate 10
bearing a methylthio group, acid-sensitive acetal 11, and
fluoride-sensitive silyl ether 12. The alkenyl tert-butylcarba-
mate bearing a disubstituted alkene, p-methoxybenzylamine,
or N-tosyl-tryptamine cyclized to afford the desired products
13−15. Moreover, amantadine derivative 16 was synthesized
from the corresponding methyl carbamate on the 5 mmol
B
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Scheme 3. Scope of Alkenyl Carbamates Affording Five-
Membered Ring Products
Scheme 4. Scope of Alkenyl Carbamates Affording
Products of Six-, Seven-, and Eight-Membered Rings
c
c
a
b
Methyl carbamate was used instead. 1.25 g (5 mmol) of starting
c
a
b
material was used. Conditions: alkenyl carbamate (0.2 mmol), C1 (3
mol %), 3 (2 equiv), 1,1,3,3-tetramethyldisiloxane (2 equiv),
benzotrifluoride (2.0 mL), room temperature, 18 h.
tert-Butyl carbamate was used instead. Methyl carbamate was used.
c
Conditions: alkenyl carbamate (0.2 mmol), C1 or C2 (3 mol %), 3
(2 equiv), 1,1,3,3-tetramethyldisiloxane (6 equiv), benzotrifluoride
(2.0 mL), room temperature, 18 h.
scale. The corresponding tert-butyl carbamate was not as
efficiently synthesized as the methyl carbamate (see SI).
We found that this method was able to form rings other
than five-membered. Various cyclic carbamates 17−19 were
prepared using the same reaction conditions from tert-butyl
carbamates bearing p-methoxyaniline units (Scheme 4). To
our great delight, these yields were improved by replacing the
catalyst with C2, which was previously developed for the
formation of medium rings by our group.4b Unfortunately,
the yield of 19 was unsatisfactory. The tert-butyl carbamates
bearing o-methoxyaniline were cyclized to afford the seven-
membered ring product 20 with C2. The methyl carbamate
bearing the p-choroaniline unit and the tert-butyl carbamate
bearing the p-methoxybenzylamine unit afforded the six-
membered ring products 21 and 23 in good yields. However,
we found that 22 and 24 were synthesized inefficiently using
this method, even though C2 was used.
We next applied the same concept to the preparation of
cyclic ureas from alkenyl isoureas. Alkenyl N-tosyl-O-
methylisoureas were synthesized from secondary amines in
three steps (see SI). We found that the p-toluenesulfonyl
group was required to produce cyclic ureas. Irrespective of
the electronic character of the substituent on the aniline unit,
the yields of imidazolidinones 25−30 were generally good to
excellent (Scheme 5). Alkenyl isoureas bearing a disubstitued
alkene or a p-methoxybenzylamine unit were also cyclized
efficiently to give 31 and 32. Six- and seven-membered cyclic
ureas 33 and 34 were also prepared by this method in good
yields. A complex product mixture was formed, and starting
material was recovered in experiments aimed at forming
eight-membered rings. We also investigated the cyclization of
an alkenyl urea with the aim of potentially producing a cyclic
urea.14b The cyclization of unpurified urea 36, synthesized
from N-allylaniline (35) and p-toluenesulfonyl isocyanate in
ethanol, afforded cyclic isourea 37 (without 26) in excellent
yield from 35. Therefore, it is clear that the dealkylative
cyclization approach is valuable from the perspective of O/N
selectivity.
With the aim of further extending synthetic utility, the p-
toluenesulfonyl group in the product needed to be removable
under mild conditions; however, we were unable to remove
this group from 39 under common reaction conditions
(Scheme 6). This observation prompted us to replace the p-
toluenesulfonyl group with other groups, such as o-nitro-
benzenesulfonyl and trifluoroacetyl. The yields of the cyclized
products from 40 and 42 were acceptable, and these
transformations were scalable (1.00 g). Both protecting
groups were removed to afford the same product 44 under
mild conditions. The seven-membered cyclic urea 47 was also
prepared by the same method. In a preliminary attempt, the
same reaction conditions were applied to the cyclization of
alkenyl phosphoramidate 48. Although there is much room
for improving both yield and selectivity, we obtained the
cyclic phosphoramidate 49, together with a complex product
mixture.
C
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Scheme 5. Scope of Alkenyl Isoureas Affording Cyclic
Ureas
Scheme 6. Additional Experiment for Cyclic Urea
Synthesis
b
a
b
C2 was used instead. (A) Conditions: alkenyl carbamate (0.2
mmol), C1 (3 mol%), 3 (2 equiv), 1,1,3,3-tetramethyldisiloxane (2
equiv), benzotrifluoride (2.0 mL), room temperature, 18 hours.
orcid.org/0000-0003-3034-1159; Email: cgehisa@
musashino-u.ac.jp
In summary, we developed a catalytic, Markovnikov-
selective, functional-group-tolerant, scalable method for the
synthesis of cyclic carbamates using a TM-HAT/RPC
approach. This reaction proceeds through the cyclization of
an alkylcobalt(IV) intermediate and dealkylation by 2,4,6-
collidine, and the mechanism was determined to be
reasonable by DFT calculations. Various cyclic carbamates
were efficiently synthesized under mild conditions. Cyclic
ureas and a cyclic phosphoramidate were also synthesized in
the same way. The HAT-initiated reaction developed here
enables the construction of medium ring carbamates and
ureas. We are currently investigating enantioselective versions
of these dealkylative cyclizations using a chiral cobalt catalyst.
Authors
Takuya Nagai − Faculty of Pharmacy, Musashino University,
Nishitokyo-shi, Tokyo 202-8585, Japan
Nao Mimata − Faculty of Pharmacy, Musashino University,
Nishitokyo-shi, Tokyo 202-8585, Japan
Yoshihiro Terada − Faculty of Pharmacy, Musashino
University, Nishitokyo-shi, Tokyo 202-8585, Japan
Chikayoshi Sebe − Faculty of Pharmacy, Musashino
University, Nishitokyo-shi, Tokyo 202-8585, Japan
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.0c01872
ASSOCIATED CONTENT
* Supporting Information
■
Notes
sı
The authors declare no competing financial interest.
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.0c01872.
ACKNOWLEDGMENTS
Experimental procedures and analytical data (1H and
■
13C NMR) for all new compounds (PDF)
We thank Prof. Kou Hiroya (Musashino University) for our
liberal research environment. We thank Dr. Yasunori Toda
(Shinshu University) for helpful advice on how to prepare
cyclic phosphoramidate. We thank Dr. Ryo Takita (Uni-
versity of Tokyo) for helpful advice on how to find TS-d.
This work was supported by JSPS KAKENHI Grant number
17K15426, the Takeda Science Foundation, and the Research
AUTHOR INFORMATION
Corresponding Author
■
Hiroki Shigehisa − Faculty of Pharmacy, Musashino
University, Nishitokyo-shi, Tokyo 202-8585, Japan;
D
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Crossover Reactions of Allylic Alcohols. J. Am. Chem. Soc. 2018,
140, 16982−16987. (v) Matos, J. L. M.; Vasquez-Cespedes, S.; Gu,
J.; Oguma, T.; Shenvi, R. A. Branch-Selective Addition of
Unactivated Olefins into Imines and Aldehydes. J. Am. Chem. Soc.
2018, 140, 16976−16981. (w) Discolo, C. A.; Touney, E. E.;
Pronin, S. V. Catalytic Asymmetric Radical−Polar Crossover
Hydroalkoxylation. J. Am. Chem. Soc. 2019, 141, 17527−17532.
(x) Green, S. A.; Huffman, T. R.; McCourt, R. O.; van der Puyl, V.;
Shenvi, R. A. Hydroalkylation of Olefins To Form Quaternary
Carbons. J. Am. Chem. Soc. 2019, 141, 7709−7714. (y) Sun, H.-L.;
Yang, F.; Ye, W.-T.; Wang, J.-J.; Zhu, R. Dual Cobalt and
Photoredox Catalysis Enabled Intermolecular Oxidative Hydro-
functionalization. ACS Catal. 2020, 10, 4983−4989. (z) Wu, B.;
Zhu, R. Radical Philicity Inversion in Co- and Fe-Catalyzed
Hydrogen-Atom-Transfer-Initiated Cyclizations of Unsaturated
Acylsilanes. ACS Catal. 2020, 10, 510−515. (aa) Zhou, X. L.;
Yang, F.; Sun, H. L.; Yin, Y. N.; Ye, W. T.; Zhu, R. Cobalt-
Catalyzed Intermolecular Hydrofunctionalization of Alkenes: Evi-
dence for a Bimetallic Pathway. J. Am. Chem. Soc. 2019, 141, 7250−
7255. (ab) Shen, X.; Chen, X.; Chen, J.; Sun, Y.; Cheng, Z.; Lu, Z.
Ligand-promoted cobalt-catalyzed radical hydroamination of alkenes.
Nat. Commun. 2020, 11, 783. (ac) Wang, Y. Y.; Bode, J. W. Olefin
Amine (OLA) Reagents for the Synthesis of Bridged Bicyclic and
Spirocyclic Saturated N-Heterocycles by Catalytic Hydrogen Atom
Transfer (HAT) Reactions. J. Am. Chem. Soc. 2019, 141, 9739−
9745. (ad) Jiang, H.; Lai, W.; Chen, H. Generation of Carbon
Radical from Iron-Hydride/Alkene: Exchange-Enhanced Reactivity
Selects the Reactive Spin State. ACS Catal. 2019, 9, 6080−6086.
(3) (a) Green, S. A.; Matos, J. L. M.; Yagi, A.; Shenvi, R. A.
Branch-Selective Hydroarylation: Iodoarene−Olefin Cross-Coupling.
J. Am. Chem. Soc. 2016, 138, 12779−12782. (b) Shevick, S. L.;
Obradors, C.; Shenvi, R. A. Mechanistic Interrogation of Co/Ni-
Dual Catalyzed Hydroarylation. J. Am. Chem. Soc. 2018, 140,
12056−12068.
(4) (a) Shigehisa, H.; Aoki, T.; Yamaguchi, S.; Shimizu, N.;
Hiroya, K. Hydroalkoxylation of Unactivated Olefins with Carbon
Radicals and Carbocation Species as Key Intermediates. J. Am.
Chem. Soc. 2013, 135, 10306−10309. (b) Shigehisa, H.; Hayashi,
M.; Ohkawa, H.; Suzuki, T.; Okayasu, H.; Mukai, M.; Yamazaki, A.;
Kawai, R.; Kikuchi, H.; Satoh, Y.; Fukuyama, A.; Hiroya, K.
Catalytic Synthesis of Saturated Oxygen Heterocycles by Hydro-
functionalization of Unactivated Olefins: Unprotected and Protected
Strategies. J. Am. Chem. Soc. 2016, 138, 10597−10604.
(5) Shigehisa, H.; Koseki, N.; Shimizu, N.; Fujisawa, M.; Niitsu,
M.; Hiroya, K. Catalytic Hydroamination of Unactivated Olefins
Using a Co Catalyst for Complex Molecule Synthesis. J. Am. Chem.
Soc. 2014, 136, 13534−13537.
(6) Shigehisa, H.; Ano, T.; Honma, H.; Ebisawa, K.; Hiroya, K.
Co-Catalyzed Hydroarylation of Unactivated Olefins. Org. Lett.
2016, 18, 3622−3625.
(7) Date, S.; Hamasaki, K.; Sunagawa, K.; Koyama, H.; Sebe, C.;
Hiroya, K.; Shigehisa, H. Catalytic Direct Cyclization of Alkenyl
Thioester. ACS Catal. 2020, 10, 2039−2045.
Foundation for Pharmaceutical Sciences. Computational
chemistry was carried out using the computer facilities at
the Research Institute for Information Technology, Kyushu
University.
REFERENCES
■
́
(1) (a) Green, S. A.; Crossley, S. W. M.; Matos, J. L. M.; Vasquez-
Cespedes, S.; Shevick, S. L.; Shenvi, R. A. The High Chemofidelity
́
of Metal-Catalyzed Hydrogen Atom Transfer. Acc. Chem. Res. 2018,
51, 2628−2640. (b) Crossley, S. W.; Obradors, C.; Martinez, R. M.;
Shenvi, R. A. Mn-, Fe-, and Co-Catalyzed Radical Hydro-
functionalizations of Olefins. Chem. Rev. 2016, 116, 8912−9000.
(2) (a) Waser, J.; Carreira, E. M. Convenient synthesis of
alkylhydrazides by the cobalt-catalyzed hydrohydrazination reaction
of olefins and azodicarboxylates. J. Am. Chem. Soc. 2004, 126, 5676−
5677. (b) Waser, J.; Nambu, H.; Carreira, E. M. Cobalt-Catalyzed
Hydroazidation of Olefins: Convenient Access to Alkyl Azides. J.
Am. Chem. Soc. 2005, 127, 8294−8295. (c) Waser, J.; Gaspar, B.;
Nambu, H.; Carreira, E. M. Hydrazines and Azides via the Metal-
catalyzed Hydrohydrazination and Hydroazidation of Olefins. J. Am.
Chem. Soc. 2006, 128, 11693−11712. (d) Gaspar, B.; Carreira, E. M.
Catalytic hydrochlorination of unactivated olefins with para-
toluenesulfonyl chloride. Angew. Chem., Int. Ed. 2008, 47, 5758−
5760. (e) Gaspar, B.; Carreira, E. M. Cobalt Catalyzed
Functionalization of Unactivated Alkenes: Regioselective Reductive
C-C Bond Forming Reactions. J. Am. Chem. Soc. 2009, 131, 13214−
13215. (f) Ishikawa, H.; Colby, D. A.; Seto, S.; Va, P.; Tam, A.;
Kakei, H.; Rayl, T. J.; Hwang, I.; Boger, D. L. Total Synthesis of
Vinblastine, Vincristine, Related Natural Products, and Key
Structural Analogues. J. Am. Chem. Soc. 2009, 131, 4904−4916.
(g) Barker, T. J.; Boger, D. L. Fe(III)/NaBH4-mediated free radical
hydrofluorination of unactivated alkenes. J. Am. Chem. Soc. 2012,
134, 13588−13591. (h) Leggans, E. K.; Barker, T. J.; Duncan, K. K.;
Boger, D. L. Iron(III)/NaBH4-mediated Additions to Unactivated
Alkenes: Synthesis of Novel 20’-vinblastine Analogues. Org. Lett.
2012, 14, 1428−1431. (i) Lo, J. C.; Gui, J.; Yabe, Y.; Pan, C. M.;
Baran, P. S. Functionalized Olefin Cross-coupling to Construct
Carbon-carbon Bonds. Nature 2014, 516, 343−348. (j) Lo, J. C.;
Yabe, Y.; Baran, P. S. A Practical and Catalytic Reductive Olefin
Coupling. J. Am. Chem. Soc. 2014, 136, 1304−1307. (k) King, S. M.;
Ma, X.; Herzon, S. B. A Method for the Selective Hydrogenation of
Alkenyl Halides to Alkyl Halides. J. Am. Chem. Soc. 2014, 136,
6884−6887. (l) Iwasaki, K.; Wan, K. K.; Oppedisano, A.; Crossley,
S. W. M.; Shenvi, R. A. Simple, Chemoselective Hydrogenation with
Thermodynamic Stereocontrol. J. Am. Chem. Soc. 2014, 136, 1300−
́
1303. (m) Crossley, S. W. M.; Barabe, F.; Shenvi, R. A. Simple,
Chemoselective, Catalytic Olefin Isomerization. J. Am. Chem. Soc.
2014, 136, 16788−16791. (n) Dao, H. T.; Li, C.; Michaudel, Q.;
Maxwell, B. D.; Baran, P. S. Hydromethylation of Unactivated
Olefins. J. Am. Chem. Soc. 2015, 137, 8046−8049. (o) Gui, J.; Pan,
C. M.; Jin, Y.; Qin, T.; Lo, J. C.; Lee, B. J.; Spergel, S. H.;
Mertzman, M. E.; Pitts, W. J.; La Cruz, T. E.; Schmidt, M. A.;
Darvatkar, N.; Natarajan, S. R.; Baran, P. S. Practical Olefin
Hydroamination with Nitroarenes. Science 2015, 348, 886−891.
(p) Ma, X.; Herzon, S. B. Non-classical Selectivities in the
Reduction of Alkenes by Cobalt-mediated Hydrogen Atom Transfer.
Chem. Sci. 2015, 6, 6250−6255. (q) Ma, X.; Herzon, S. B.
Intermolecular Hydropyridylation of Unactivated Alkenes. J. Am.
Chem. Soc. 2016, 138, 8718−8721. (r) Obradors, C.; Martinez, R.
M.; Shenvi, R. A. Ph(i-PrO)SiH2: An Exceptional Reductant for
Metal-Catalyzed Hydrogen Atom Transfers. J. Am. Chem. Soc. 2016,
138, 4962−4971. (s) Shen, Y.; Qi, J.; Mao, Z.; Cui, S. Fe-Catalyzed
Hydroalkylation of Olefins with para-Quinone Methides. Org. Lett.
2016, 18, 2722. (t) Lo, J. C.; Kim, D.; Pan, C. M.; Edwards, J. T.;
Yabe, Y.; Gui, J.; Qin, T.; Gutierrez, S.; Giacoboni, J.; Smith, M. W.;
Holland, P. L.; Baran, P. S. Fe-Catalyzed C-C Bond Construction
from Olefins via Radicals. J. Am. Chem. Soc. 2017, 139, 2484−2503.
(u) Touney, E. E.; Foy, N. J.; Pronin, S. V. Catalytic Radical-Polar
(8) (a) Anderson, S. N.; Ballard, D. H.; Chrzastowski, J. Z.; Dodd,
D.; Johnson, M. D. Inversion of Configuration in the Nucleophilic
Displacement of Cobalt from Alkylcobalt(IV) Complexes and Its
Relevance to the Halogenation of the Corresponding Alkylcobalt-
(III) Complexes. J. Chem. Soc., Chem. Commun. 1972, 685−686.
(b) Magnuson, R. H.; Halpern, J.; Levitin, I. Y.; Vol’pin, M. E.
Stereochemistry of the Nucleophilic Cleavage of Cobalt−carbon
Bonds in Organocobalt(IV) Compounds. J. Chem. Soc., Chem.
Commun. 1978, 44−46. (c) Vol’pin, M. E.; Levitin, I. Y.; Sigan, A.
L.; Halpern, J.; Tom, G. M. Reactivity of Organocobalt(IV) Chelate
Complexes Toward Nucleophiles: Diversity of Mechanisms. Inorg.
Chim. Acta 1980, 41, 271−277.
(9) Mukhtar, T. A.; Wright, G. D. Streptogramins, Oxazolidinones,
and Other Inhibitors of Bacterial Protein Synthesis. Chem. Rev.
2005, 105, 529−542.
E
https://dx.doi.org/10.1021/acs.orglett.0c01872
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Organic Letters
pubs.acs.org/OrgLett
Letter
(10) Young, S. D.; Britcher, S. F.; Tran, L. O.; Payne, L. S.;
Lumma, W. C.; Lyle, T. A.; Huff, J. R.; Anderson, P. S.; Olsen, D.
B.; Carroll, S. S. L-743, 726 (DMP-266): a novel, highly potent
nonnucleoside inhibitor of the human immunodeficiency virus type
1 reverse transcriptase. Antimicrob. Agents Chemother. 1995, 39,
2602−2605.
11926−11931. (g) Zhang, H.; Tian, P.; Ma, L.; Zhou, Y.; Jiang, C.;
Lin, X.; Xiao, X. Remote Directed Isocyanation of Unactivated
C(sp3)−H Bonds: Forging Seven-Membered Cyclic Ureas Enabled
by Copper Catalysis. Org. Lett. 2020, 22, 997−1002.
(11) Cronan, J. E. Advances in synthesis of biotin and assembly of
lipoic acid. Curr. Opin. Chem. Biol. 2018, 47, 60−66.
(12) Chen, S.-B.; Gao, G.-Y.; Leung, H.-W.; Yeung, H.-W.; Yang,
J.-S.; Xiao, P.-G. Aquiledine and Isoaquiledine, Novel Flavonoid
Alkaloids from Aquilegia ecalcarata. J. Nat. Prod. 2001, 64, 85−87.
(13) (a) Robles-Machín, R.; Adrio, J.; Carretero, J. C. Gold-
Catalyzed Synthesis of Alkylidene 2-Oxazolidinones and 1,3-Oxazin-
2-ones. J. Org. Chem. 2006, 71, 5023−5026. (b) Jagtap, S. R.; Patil,
Y. P.; Fujita, S.-I.; Arai, M.; Bhanage, B. M. Heterogeneous base
catalyzed synthesis of 2-oxazolidinones/2-imidiazolidinones via
transesterification of ethylene carbonate with β-aminoalcohols/1,2-
diamines. Appl. Catal., A 2008, 341, 133−138. (c) Ishida, T.;
Kobayashi, R.; Yamada, T. Novel Method of Tetramic Acid
Synthesis: Silver-Catalyzed Carbon Dioxide Incorporation into
Propargylic Amine and Intramolecular Rearrangement. Org. Lett.
2014, 16, 2430−2433. (d) Paddock, R. L.; Adhikari, D.; Lord, R. L.;
Baik, M.-H.; Nguyen, S. T. [(Salcen)CrIII + Lewis base]-catalyzed
synthesis of N-aryl-substituted oxazolidinones from epoxides and
aryl isocyanates. Chem. Commun. 2014, 50, 15187−15190.
̈
(e) Zhang, Y.; Zhang, Y.; Ren, Y.; Ramstrom, O. Synthesis of
chiral oxazolidinone derivatives through lipase-catalyzed kinetic
resolution. J. Mol. Catal. B: Enzym. 2015, 122, 29−34. (f) Wang,
P.; Qin, J.; Yuan, D.; Wang, Y.; Yao, Y. Synthesis of Oxazolidinones
from Epoxides and Isocyanates Catalyzed by Rare-Earth-Metal
Complexes. ChemCatChem 2015, 7, 1145−1151. (g) Niemi, T.;
́
Perea-Buceta, J. E.; Fernandez, I.; Hiltunen, O.-M.; Salo, V.;
̈
̈
Rautiainen, S.; Raisanen, M. T.; Repo, T. A One-Pot Synthesis of N-
Aryl-2-Oxazolidinones and Cyclic Urethanes by the Lewis Base
Catalyzed Fixation of Carbon Dioxide into Anilines and
Bromoalkanes. Chem.
- Eur. J. 2016, 22, 10355−10359.
̈
(h) Zhang, Y.; Zhang, Y.; Xie, S.; Yan, M.; Ramstrom, O. Lipase-
catalyzed kinetic resolution of 3-phenyloxazolidin-2-one derivatives:
Cascade O- and N-alkoxycarbonylations. Catal. Commun. 2016, 82,
11−15. (i) Toda, Y.; Gomyou, S.; Tanaka, S.; Komiyama, Y.;
Kikuchi, A.; Suga, H. Tetraarylphosphonium Salt-Catalyzed Syn-
thesis of Oxazolidinones from Isocyanates and Epoxides. Org. Lett.
́
2017, 19, 5786−5789. (j) Niemi, T.; Fernandez, I.; Steadman, B.;
Mannisto, J. K.; Repo, T. Carbon dioxide-based facile synthesis of
cyclic carbamates from amino alcohols. Chem. Commun. 2018, 54,
3166−3169. (k) Yousefi, R.; Struble, T. J.; Payne, J. L.; Vishe, M.;
Schley, N. D.; Johnston, J. N. Catalytic, Enantioselective Synthesis of
Cyclic Carbamates from Dialkyl Amines by CO2-Capture:
Discovery, Development, and Mechanism. J. Am. Chem. Soc. 2019,
141, 618−625.
̈
̃
(14) (a) Streuff, J.; Hovelmann, C. H.; Nieger, M.; Muniz, K.
Palladium(II)-Catalyzed Intramolecular Diamination of Unfunction-
alized Alkenes. J. Am. Chem. Soc. 2005, 127, 14586−14587. (b) Rao,
W.-H.; Yin, X.-S.; Shi, B.-F. Catalyst-Controlled Amino- versus Oxy-
Acetoxylation of Urea-Tethered Alkenes: Efficient Synthesis of
Cyclic Ureas and Isoureas. Org. Lett. 2015, 17, 3758−3761.
(c) Kondoh, A.; Kamata, Y.; Terada, M. Synthesis of Enantioen-
riched γ-Amino-α,β-unsaturated Esters Utilizing Palladium-Catalyzed
Rearrangement of Allylic Carbamates for Direct Application to
Formal [3 + 2] Cycloaddition. Org. Lett. 2017, 19, 1682−1685.
(d) Hinds, E. M.; Wolfe, J. P. A Cross-Metathesis/Aza-Michael
Reaction Strategy for the Synthesis of Cyclic and Bicyclic Ureas. J.
Org. Chem. 2018, 83, 10668−10676. (e) Wu, M.-S.; Fan, T.; Chen,
S.-S.; Han, Z.-Y.; Gong, L.-Z. Pd(II)-Catalyzed Asymmetric
Oxidative 1,2-Diamination of Conjugated Dienes with Ureas. Org.
Lett. 2018, 20, 2485−2489. (f) Struble, T. J.; Lankswert, H. M.;
Pink, M.; Johnston, J. N. Enantioselective Organocatalytic Amine-
Isocyanate Capture-Cyclization: Regioselective Alkene Iodoamina-
tion for the Synthesis of Chiral Cyclic Ureas. ACS Catal. 2018, 8,
F
https://dx.doi.org/10.1021/acs.orglett.0c01872
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