- Facile direct synthesis of unsymmetrical ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines using DABAL-Me3
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A practical synthetic method for the direct synthesis of unsymmetrically substituted ureas from N-Alloc-, N-Cbz-, and N-Boc-protected amines is described. In this study, efficient direct conversion of the Alloc-, Cbz-, and Boc-carbamate compounds to ureas was achieved in the presence of DABAL-Me3, an air stable and easily handled reagent. Using this reaction method, both protected aromatic and aliphatic amines were successfully transformed into various trisubstituted and tetrasubstituted ureas with high yields without side product. Our findings offer promising guidelines for direct preparation of useful ureas from N-Alloc-, N-Cbz-, and N-Boc-carbamates.
- Kang, Soosung,Kim, Hee-Kwon
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p. 4036 - 4046
(2018/06/13)
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- Ruthenium-Catalyzed Urea Synthesis Using Methanol as the C1 Source
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An unprecedented protocol for urea synthesis directly from methanol and amine was accomplished. The reaction is highly atom-economical, producing hydrogen as the sole byproduct. Commercially available ruthenium pincer complexes were used as catalysts. In addition, no additive, such as a base, oxidant, or hydrogen acceptor, was required. Furthermore, unsymmetrical urea derivatives were successfully obtained via a one-pot, two-step reaction.
- Kim, Seung Hyo,Hong, Soon Hyeok
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supporting information
p. 212 - 215
(2016/02/03)
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- Palladium-mediated oxidative carbonylation reactions for the synthesis of 11C-radiolabelled ureas
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Palladium(II)-mediated oxidative carbonylation reactions have been used to synthesize 11C-radiolabelled ureas via the coupling of amines with [11C]carbon monoxide, in a one-pot process. Following trapping of 11CO in a solution of copper(I) tris(3,5-dimethylpyrazolyl)borate, homocoupling reactions of primary aliphatic amines proceed in the presence of Pd(PPh3)2Cl2 to give the corresponding N,N-disubstituted [11C]ureas. Secondary amines do not produce the corresponding N,N,N,N-tetrasubsituted [11C]ureas under these conditions. This difference in reactivity allows for the formation of unsymmetrical N,N',N'-trisubstituted [11C]ureas using a mixture of a primary amine and a reactive secondary amine. The potential use of this method in positron emission tomography (PET) was demonstrated by the synthesis of the M1 muscarinic acetylcholine receptor radiotracer, [11C-carbonyl] GSK1034702.
- Kealey, Steven,Husbands, Stephen M.,Bennacef, Idriss,Gee, Antony D.,Passchier, Jan
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p. 202 - 208
(2014/05/06)
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