Hindered Ureas as Masked Isocyanates: Facile Carbamoylation of Nucleophiles under Neutral Conditions

Carbolithiation of N-alkenyl ureas and N-alkenyl carbamates

“…In principle, the urea products 2 , 4 and 6 could be solvolysed to liberate free amines, as has been demonstrated for related compounds [4,15,20]. However, we reasoned that the related tert -butyloxycarbonyl-substituted carbamates would give more readily manipulated carbamate products bearing a standard Boc protecting group, providing they too could be carbolithiated and trapped without rearrangement.…”

Spontaneous and Direct Transformation of <i>N</i>,<i>O</i>-Diaryl Carbamates into <i>N</i>,<i>N</i>′-Diarylureas

“…1 H-NMR and mp were consistent with reported data. 29,30) 4-Methoxyphenyl N-(4-Methylphenyl)carbamate (3g) mp 164.5-165.0°C; 1 H-NMR (300 MHz, CDCl 3 ) 2.32 (s, 3H), 3.80 (s, 3H), 6.90 (d, J=9.0 Hz, 2H), 7.08-7.14 (m, 4H), 7.32 (m, 2H).…”

(Tosylimino)phenyl-λ3-iodane as a Reagent for the Synthesis of Methyl Carbamates via Hofmann Rearrangement of Aromatic and Aliphatic Carboxamides

“…20 Reaction of hexanamide 2s (9 mg, 0.075 mmol) according to the general procedure afforded 10 mg (92%) of product 4s, isolated as a colorless oil: 1 Methyl N-tert-Butylcarbamate (4u). 21 Reaction of trimethylacetamide 2u (15 mg, 0.15 mmol) according to the general procedure afforded 14 mg (72%) of product 4u, isolated as a colorless oil: 1 p-Isocyanatotoluene (3a). N-(4-Methylphenylsulfonyl)-iminophenyl-λ 3 -iodane 1 (34 mg, 0.09 mmol) was added to a solution of p-toluamide 2a (10 mg, 0.075 mmol) in dichloromethane (1.5 mL) and stirred at room temperature for 0.5 h. After completion of the reaction, the mixture was concentrated and separated by preparative TLC (hexane−ethyl acetate = 2: 1) to afford 8 mg (80%) of pisocyanatotoluene 3a, isolated as a brown oil: 1 H NMR (500 MHz, CDCl 3 ) δ 7.22 (d, J = 8.5 Hz, 2H), 7.14 (d, J = 8.5 Hz, 2H), 2.33 (s, 3H).…”