Über die Bildung ysmmetrisch dialkylierter Harnstoffe durch Erhitzen der entsprechenden Carbaminate

Quantitative Determination of Alkaloids in Lotus Flower (Flower Buds of Nelumbo nucifera) and Their Melanogenesis Inhibitory Activity

“…It is well known that ammonia, primary amines, or secondary amines ( A ) absorb CO 2 to transform into the corresponding carbamic acids ( B ), which easily react with the original amines to produce stable carbamic acid ammonium salts and ( C ) as shown in Figure 4 [15,16,17,18,19,20,21,22,23,24]. Therefore, it is reasonable to anticipate that the product 2′′ forms via an acid-base reaction between original amine 2 and an unstable carbamic acid ( 2′ ), which was obtained by the CO 2 absorption reaction with the nitrogen atom of 2 .…”

Frustrated Lewis pair chemistry of carbon, nitrogen and sulfur oxides

“…16,17 Subsequent addition of borane results in binding of the CO 2 fragment to B affording complexes of the general formula (C 3 H 2 (NR) 2 ) CO 2 BR 3 . Interestingly, Tamm and co-workers have shown that the carbene-borane adduct C 3 H 2 (N t Bu) 2 /B(C 6 H 3 (CF 3 ) 2 ) 3 (22) behaves as an FLP reacting with CO 2 to give (C 3 H 2 (N t Bu) 2 ) CO 2 B(C 6 H 3 (CF 3 ) 2 ) 3 (23). 18 In a similar fashion, the FLPs, C 3 R 2 (N t Bu) 2 /B(C 6 F 5 ) 3 (R ¼ H (24), Me ( 25)) afford synthetic routes to the analogous species (C 3 R 2 (N t Bu) 2 )CO 2 B(C 6 F 5 ) 3 (R ¼ H (26), Me ( 27)) (Scheme 5).…”

“…In a similar sense, primary and secondary amines are known to react with CO 2 to generate carbamates, [20][21][22] though PhCH 2 NMe 2 is unreactive with CO 2 . [23][24][25] However, the FLP derived from the adduct (PhCH 2 NMe 2 )B(C 6 F 5 ) 3 (28) reacts with CO 2 to give the FLP adduct PhCH 2 NMe 2 (CO 2 )B(C 6 F 5 ) 3 (29). 26 The resulting N-C and B-O bond lengths are 1.545(2) and 1.550 (2) Å, respectively, and 29 gives rise to an IR ñ(C]O) stretching band of 1822 cm À1 , markedly lower than the corresponding band for free CO 2 (2345 cm À1 ).…”

Chemistry and heterocyclization of carbohydrazides

“…The interaction of phosgene and hydrazine hydrate in refluxing benzene afforded carbohydrazides as dihydrochloride [24]. Also, hydrazinolysis of carbazic acid [25] and cyanuric acid [26] gave carbohydrazides.…”