Direct synthesis of N-methylurethanes from primary amines with dimethyl carbonate

Tundo, Pietro; Bressanello, S.; Loris, Alessandro; Sathicq, Ángel Gabriel

doi:10.1351/pac200577101719

Cited by 35 publications

(34 citation statements)

References 6 publications

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“…As observed with primary amines and anilines, 4 phenylhydrazine reacts in a similar manner; however, in this case there is the equivalent of both a primary and a secondary amine. When KO-t-Bu is used, there are two likely explanations for the initial key reaction, which produces 6 (Scheme 2, step i).…”

Section: Scheme 3 Formation Of Carbazatesupporting

confidence: 55%

“…4 Base catalysts such as potassium tert-butoxide, sodium methoxide, and cesium carbonate effected carboxymethylation of the phenyl-substituted nitrogen to produce 6 (Scheme 2, i), albeit at different rates and selectivity. The rate of the reactions proceeded in order of base strength, i.e., KO-t-Bu > NaOMe > Cs 2 CO 3 > K 2 CO 3 (no reaction).…”

Section: Tundop@univeit Received August 31 2007mentioning

confidence: 99%

“…When Ti(O-t-Bu) 4 was used, the reaction took considerably more time and the selectivity toward carbazate 11 over carbazate 6 was 80% after complete conversion of phenylhydrazine (Table 1, entry 7). In either case, apparently these metal complexes activated phenylhydrazine for attack as a hard nucleophile, more prominently at N-2, which is different from the activation by a Brönsted base.…”

Section: Scheme 3 Formation Of Carbazatementioning

confidence: 99%

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Reaction of the Ambident Electrophile Dimethyl Carbonate with the Ambident Nucleophile Phenylhydrazine

2008

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To explore the ambident electrophilic reactivity of dimethyl carbonate (DMC), reactions with the ambident nucleophile phenylhydrazine were investigated. When a Brönsted base was used, selective carboxymethylation occurred at N-1, after that several other compounds were produced selectively utilizing various conditions. Formation of these compounds was explained by using the Hard-Soft Acid-Base (HSAB) theory. Catalysis by some metal salts altered the reactivity of phenylhydrazine, which effected selective carboxymethylation at N-2 of phenylhydrazine instead.Dimethyl carbonate (DMC) is a well-known nontoxic reagent and solvent that has been used for many Green applications, namely the substitution of toxic reagents such as methyl halides and phosgene for the selective methylation and carboxymethylation, respectively, of numerous nucleophiles. 1 Both transformations are possible owing to the two nonequivalent electrophilic centers of DMC, making it an ambident electrophile. Selectivity toward either center can be attributed to the HardSoft Acid-Base (HSAB) theory, introduced by Pearson. 2 In the context of DMC, the theory can be simply applied by suggesting DMC will carboxymethylate (hard reaction) hard nucleophiles or methylate (soft reaction) soft nucleophiles. It should be pointed out that this classification is a relative assignment for the differing reactivities of the two electrophilic centers of DMC.A prime example that demonstrates both hard and soft nucleophilicity in a tandem reaction, and is also relevant to this report, is the reaction of arylacetonitriles with DMC. 3 From the starting material, e.g., phenylacetonitrile, an anion is generated with a Brönsted base; the anion is a hard nucleophile and thus reacts with DMC to produce the carboxymethylated arylacetonitrile 2. Bearing the carboxylate group, the reactive carbon anion is rendered a soft nucleophilic center and undergoes methylation to produce the methyl carboxymethylated arylacetonitrile 3. Reaction between MeOH and 3 results in the formation of 2-methyl-2-phenylacetonitrile (4), which does not readily undergo methylation because the loss of the carboxymethyl moiety renders the carbon a hard nucleophilic center, which only permits the carboxymethylation to reproduce 3. Significantly, the reaction was carried out with DMC as a solvent/reagent; after complete conversion the selectivity for the mono-methylated product 4 was >99%.DMC has also been shown to react analogously with other nucleophiles, such as amino compounds. 4 In an effort to explore this concept further, a more complex class of nucleophile was sought. In particular, ambident nucleophiles were of interest due to the appealing concept of exploring reactions of ambident nucleophiles with ambident electrophiles.Phenylhydrazine was our first choice for an ambident nucleophile. On face value, it is a relatively simple molecule. It possesses two adjacent nitrogens; however, they differ in reactivity due to the phenyl substituent at N-1. In the literature there are some reports of alkylati...

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Section: Scheme 3 Formation Of Carbazatesupporting

confidence: 55%

Section: Tundop@univeit Received August 31 2007mentioning

confidence: 99%

Section: Scheme 3 Formation Of Carbazatementioning

confidence: 99%

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Reaction of the Ambident Electrophile Dimethyl Carbonate with the Ambident Nucleophile Phenylhydrazine

2008

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“…The physical characteristics and NMR spectra of compounds 15 and 16 are coherent with data already reported in the literature [12]. The observed conversion of aniline into its cyclic derivative ( Table 2, entries 5 and 6) is lower than that of hydrazine or benzylamine as usually the aromatic amines are weaker nucleophiles than aliphatic ones and as such do not react as readily [37]. It should be noted that although the yields obtained are comparable to those already reported in the literature, the proposed synthetic pathway is greener, simpler, and faster, and it utilizes inexpensive, readily available starting materials [11,12].…”

Section: Reaction Of Benzylamine With Dimethyl-2-methyl-propane-13-dsupporting

confidence: 85%

“…In the last 20 years, dimethyl carbonate (DMC) and its derivatives have become well-known substitutes for phosgene and alkyl halides [25] and have been shown to effectively react with aliphatic [26,27] and aromatic [27,28] amines and hydrazines [29] to give a wide range of carbamates and methyl amines. DMC is a green reagent and solvent produced industrially by CO 2 insertion into an epoxide, followed by cleavage of the resulting cyclic carbonate with methanol [30].…”

Section: Introductionmentioning

confidence: 99%

Cyclization reaction of amines with dialkyl carbonates to yield 1,3-oxazinan-2-ones

McElroy

Aricò

Benetollo³

et al. 2011

Pure and Applied Chemistry

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A number of six-membered cyclic carbamates (oxazinanones) were synthesized from the reaction of a primary amine or hydrazine with a dicarbonate derivative of 1,3-diols in a one-pot reaction, in good yield, short time span, and in the absence of a solvent. The reaction proceeds in two steps: an intermolecular reaction to give a linear intermediate and an intramolecular cyclization to yield the cyclic carbamate. This is the first example of a carbonate reacting selectively and sequentially, firstly at the carbonyl center to form a linear carbamate and then as a leaving group to yield a cyclic carbamate.

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Diethyl Carbonate

Krapcho

Gorin

2015

Encyclopedia of Reagents for Organic Synthesis

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Direct synthesis of N-methylurethanes from primary amines with dimethyl carbonate

Cited by 35 publications

References 6 publications

Reaction of the Ambident Electrophile Dimethyl Carbonate with the Ambident Nucleophile Phenylhydrazine

Reaction of the Ambident Electrophile Dimethyl Carbonate with the Ambident Nucleophile Phenylhydrazine

Cyclization reaction of amines with dialkyl carbonates to yield 1,3-oxazinan-2-ones

Diethyl Carbonate

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