1,720,996 research outputs found
Phosgene substitution. Selective carbomethoxylation of aliphatic amines via Sc(OTf)3-promoted activation of dimethylcarbonate
No full textCarbomethoxylating reactivity of methylphenylcarbonate toward aromatic amines in the presence of Group 3 metal (sc, La) triflate catalysts
No full text“Highly selective carbamation of aliphatic diamines under mild conditions using Sc(OTf)3 as catalyst and dimethyl carbonate as a phosgene substitute” , 2006, 66(1-2), 72-80
No full textSc(OTf)3 is an effective catalyst for bis-carbomethoxylation of aliphatic diamines with dimethyl carbonate (DMC) under very mild
conditions. At ambient temperature (293 K), in the presence of Sc(OTf)3, aliphatic diamines, such as 1,6-diaminohexane (1), 1,4-diaminobutane
(2), 1,3-diaminopropane (3), meta-xylylenediamine (4) and para-xylylenediamine (5), react with DMC to afford the corresponding dicarbamates
in high yields. The carbomethoxylation reaction is highly selective (100%). Under the used working conditions, side-reactions,
such as formation of ureas and/or N-methyl derivatives, are repressed. The starting catalyst, Sc(OTf)3, modifies during the catalytic process and
converts into Sc-methoxo species by losing OTf groups, as the isolation of unprecedented mono-urethane triflic salts, (MeO(O)CNH–R–
NH3)O3SCF3 (R = –(CH2)6–, meta-C6H4(CH2)2–), also indicates. The modified catalyst can be recovered at the end of the reaction and
recycled
Group 3 metal (Sc, La) triflates as catalysts for amine carbomethoxylation under mild conditions
No full text“Phosgene-free synthesis of carbamate esters under mild conditions: Carbomethoxylation of amines promoted by group 3 metal triflates”
No full text
Sc(OTf)3-catalyzed carbomethoxylation of aliphatic amines with dimethyl carbonate (DMC): DMC activation by η1-O(C=O) coordination to Sc(III) and its relevance to catalysis
No full textThe role of metal center in the Sc(OTf)3-catalyzed carbomethoxylation of aliphatic amines with DMC has been investigated. We have shown
that the catalytic formation of carbamate ester is promoted by coordination of DMC to scandium(III) ion through the carbonyl oxygen atom. The
ability of DMC to coordinate to Sc(III) has been proved by IR and NMR spectroscopy and fully demonstrated also by the isolation, for the first
time, of a DMC–metal complex characterized as (η1-O(C=O)–DMC)Sc(OTf)3. A relationship has been shown between the coordination mode
of DMC to Sc(III) and the reactivity of coordinated organic carbonate: coordination of DMC to Sc(III) activates both carbonyl group and O–CH3
moieties of the carbonic acid diester and enhances not only the carbomethoxylating but also the methylating activity of the ambident electrophile
(DMC), as documented by the different selectivity exhibited by the catalyst in the aminolysis reaction of DMC with benzylamine and aniline,
respectively
Methylphenylcarbonate as carbomethoxylating agent of aromatic amines in the presence of Group 3 metal (Sc, La) triflate catalysts??
No full textSuperbase promoted direct N-Carbonylation of pyrrole with carbonic acid diesters
No full textCarbonic acid diesters have been investigated as carbonylating agents in the direct reaction with pyrrole (HetNH). In the presence of
superbases (DBU, P1-t-Bu, BTPP) as catalysts, the heteroaromatic substrate can be N-carbonylated by direct reaction with carbonic acid
diesters under not-severe experimental conditions. The carbonylation reaction makes accessible pyrrole N-carbonyl derivatives (Het-
NC(O)OR, (HetN)2CO) selectively through a simple straightforward way, which offers a safe eco-friendly alternative to the traditional
synthetic methods based on hazardous phosgene or phosgene-derivatives
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