A novel synthesis of isocyanates and ureas via β-elimination of haloform

Braverman, S.; Cherkinsky, M.; Kedrova, L. K.; Reiselman, A.

doi:10.1016/s0040-4039(99)00372-x

Cited by 42 publications

(24 citation statements)

References 11 publications

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“…Di-tert-butyldicarbonate 8, (BOC) 2 O, a useful protecting reagent for primary amines, has been used to give both symmetrical and unsymmetrical ureas, starting from primary amines, 14 in the presence of either a strong or mild base. 15 Trihalomethylacetyl chlorides, 9, 16 and phenyl chloroformate 10, 17 react with amines at the acylic position to give the corresponding phenylcarbamate and trihalomethylamide; both reagents establish their reactivity on the ease of elimination of phenoxide and haloform leaving groups, yielding the isocyanate reactive intermediate, which reacts with the second equivalent of amine. N,N 0 -Carbonyldiimidazole (13, CDI) 18 and N,N 0 -carbonyldibenzotriazole ( 14) 19 have been used in the synthesis of di-, tri-and tetra-symmetrical and unsymmetrical substituted ureas.…”

Section: Lorenzo Moscamentioning

confidence: 99%

Anion recognition by hydrogen bonding: urea-based receptors

2010

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Since 1992 a variety of urea-based anion receptors have been synthesised, of varying complexity and sophistication. This critical review will focus on some distinctive aspects of anion recognition by urea derivatives, with a special reference to: (i) design and synthesis, (ii) methodologies for the investigation of the receptor-anion interaction in solution, (iii) the interpretation of the solution behaviour on the basis of the structural interplay between the receptor and the anion. It will be shown that the efficiency of urea as a receptor subunit depends on the presence of two proximate polarised N-H fragments, capable (i) of chelating a spherical anion or (ii) of donating two parallel H-bonds to the oxygen atoms of a carboxylate or of an inorganic oxoanion, a property which is shared with other diamides, e.g. squaramide. The wide use of urea in the design of neutral anion receptors seems to depends on the ease of its synthesis, in particular through the reaction of a primary amine group with an isocyanate, which allows the high-yield preparation of symmetrically and unsymmetrically substituted derivatives (83 references).

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Section: Lorenzo Moscamentioning

confidence: 99%

Anion recognition by hydrogen bonding: urea-based receptors

2010

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“…Carbamates are common structural motifs in pharmaceuticals . For example, the herbicide Swep 3 db can be accessed directly in one step from dichlorobenzene and ethyl carbamate in a 65 % isolated yield. Other amides, such as benzamide and acetamide also gave satisfactory yields of the corresponding N‐arylated products.…”

Section: Methodsmentioning

confidence: 99%

Teaching Old Compounds New Tricks: DDQ‐Photocatalyzed C−H Amination of Arenes with Carbamates, Urea, and N‐Heterocycles

Das

Natarajan

König

2017

Chemistry A European J

108

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The C−H amination of benzene derivatives was achieved using DDQ as photocatalyst and BocNH2 as the amine source under aerobic conditions and visible light irradiation. Electron‐deficient and electron‐rich benzenes react as substrates with moderate to good product yields. The amine scope of the reaction comprises Boc‐amine, carbamates, pyrazoles, sulfonimides and urea. Preliminary mechanistic investigations indicate arene oxidation by the triplet of DDQ to radical cations with different electrophilicity and a charge transfer complex between the amine and DDQ as intermediate of the reaction.

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“…Most of the synthetic methods reported for urea derivatives use highly toxic, unstable and expensive chemicals viz., azide, carbamate, phosgene, isocyanate and carbonylimidazole derivatives . Other safe methods consist oxidative carbonylation of amines with CO and direct carbonylation of amines with carbon dioxide .…”

Section: Coupling Chemistrymentioning

confidence: 99%

“…[80,81] Most of the synthetic methods reported for urea derivatives use highly toxic, unstable and expensive chemicals viz., azide, carbamate, phosgene, isocyanate and carbonylimidazole derivatives. [30,[82][83][84][85] Other safe methods consist oxidative carbonylation of amines with CO [86,87] and direct carbonylation of amines with carbon dioxide. [88] The problems associated with other routes are harsh reaction conditions and metal catalysts used are expensive.…”

Section: Urea and Substituted Urea Synthesismentioning

confidence: 99%

Copper Catalyzed C−H Activation

Kantam

Gadipelly

Deshmukh

et al. 2018

The Chemical Record

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Activation of C−H bonds and their application in cross coupling chemistry has received a wider interest in recent years. The conventional strategy in cross coupling reaction involves the pre‐functionalization step of coupling reactants such as organic halides, pseudo‐halides and organometallic reagents. The C−H activation facilitates a simple and straight forward approach devoid of pre‐functionalization step. This approach also addresses the environmental and economical issues involved in several chemical reactions. In this account, we have reported C−H bond activation of small organic molecules, for example, formamide C−H bond can be activated and coupled with β‐dicarbonyl or 2‐carbonyl substituted phenols under oxidative conditions to yield carbamates using inexpensive copper catalysts. Phenyl carbamates were successfully synthesized in moderate to good yields by cross dehydrogenative coupling (CDC) of phenols with formamides using copper catalysts in presence of a ligand. We have also prepared unsymmetrical urea derivatives by oxidative cross coupling of formamides with amines using copper catalysts. Synthesis of N,N‐dimethyl substituted amides, 5‐substituted‐γ‐lactams and α‐acyloxy ethers was carried out from carboxylic acids using recyclable CuO nanoparticles. Copper nanoparticles afforded N‐aryl‐γ‐amino‐γ‐lactams by oxidative coupling of aromatic amines with 2‐pyrrolidinone. Reusable transition metal HT‐derived oxide catalyst was used for the synthesis of N,N‐dimethyl substituted amides by the oxidative cross‐coupling of carboxylic acids and substituted benzaldehydes. Overview of our work in this area is summarized.

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A novel synthesis of isocyanates and ureas via β-elimination of haloform

Cited by 42 publications

References 11 publications

Anion recognition by hydrogen bonding: urea-based receptors

Anion recognition by hydrogen bonding: urea-based receptors

Teaching Old Compounds New Tricks: DDQ‐Photocatalyzed C−H Amination of Arenes with Carbamates, Urea, and N‐Heterocycles

Copper Catalyzed C−H Activation

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