- Electronic Activity Tuning of Acyclic Guanidines for Lactide Polymerization
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Novel aromatic guanidine-based organocatalysts for the ring-opening of l-lactide were synthesized and applied in comprehensive polymerization experiments and kinetic studies. The introduction of electronically active substituents led to a significant chan
- Eisenreich, Fabian,Viehmann, Philipp,Müller, Fabian,Hecht, Stefan
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- Lanthanum(III) Trifluoromethanesulfonate Catalyzed Direct Synthesis of Ureas from N-Benzyloxycarbonyl-, N -Allyloxycarbonyl-, and N -2,2,2-Trichloroethoxycarbonyl-Protected Amines
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A novel lanthanum triflate mediated conversion of N -benzyloxycarbonyl-, N -allyloxycarbonyl-, and N -trichloroethoxycarbonyl-protected amines into nonsymmetric ureas was discovered. In this study, lanthanum triflate was found to be an effective catalyst for preparing various nonsymmetric ureas from protected amines. A variety of protected aromatic and aliphatic carbamates reacted readily with various amines in the presence of lanthanum triflate to generate the desired ureas in high yields. This result demonstrated that this novel lanthanum triflate catalyzed preparation of ureas from Cbz, Alloc, and Troc carbamates can be employed for the formation of various urea structures.
- Bui, Tien Tan,Kim, Hee-Kwon
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supporting information
p. 997 - 1002
(2020/06/17)
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- Chemoselective isocyanide insertion into the N-H bond using iodine-DMSO: Metal-free access to substituted ureas
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Insertion of isocyanides into the N-H bond gives access to many medicinally important and structurally diverse complex nitrogen-containing heterocycles. Although the transition metal catalyzed isocyanide insertion into the N-H bond is very common, polymerization of isocyanides in the presence of a transition metal and their strong coordination with metals are the common drawbacks. On the other hand, the inertness of most of the isocyanides towards amines in the absence of a metal catalyst has stymied the growth of the metal-free approach for isocyanide insertion into amines. As a result, only a handful of metal catalysed methods with limited substrate scopes have been reported for the synthesis of ureas via isocyanide insertion into amines and no metal-free version has been reported yet. Interestingly, chemoselective isocyanide insertion into amines has not been reported in the literature. We employed the I2-DMSO reagent system for the chemoselective synthesis of ureas, where isocyanides react with aliphatic amines only, while aromatic amines need a nucleophilic activator (DABCO) to facilitate the formation of ureas. This method gave direct and chemoselective access to ureas by evading the commonly used yet toxic isocyanates.
- Bora, Porag,Bez, Ghanashyam
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supporting information
p. 8363 - 8366
(2018/08/03)
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- A high yielding, one-pot synthesis of substituted ureas from the corresponding amines using Mitsunobu's reagent
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A Mitsunobu-based protocol has been developed for the synthesis of symmetrically and unsymmetrically substituted ureas from a variety of primary and secondary amines using gaseous carbon dioxide, in good to excellent yields. This protocol is mild and efficient compared to other reported methods.
- Chaturvedi, Devdutt,Mishra, Nisha,Mishra, Virendra
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experimental part
p. 267 - 270
(2009/05/26)
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- Super fast cobalt carbonyl-mediated synthesis of ureas
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Fast cobalt carbonyl-mediated generation of ureas from primary amines was performed using high-density microwave irradiation. This enhanced method permitted the preparation of symmetrical ureas in good yields and unsymmetrical ureas in moderate yields. Th
- Enquist, Per-Anders,Nilsson, Peter,Edin, Johan,Larhed, Mats
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p. 3335 - 3339
(2007/10/03)
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