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Formation of Intermediate and By-products in Synthesis of 4,4′-Methylenedimethyldiphenylcarbamate

“…Several studies have been devoted to exploring new catalyst and to optimizing reaction condition for the step [10][11][12][13][14], which are necessary to consummate the process. However, few reports have dealt with the research on formation of the intermediate and by-products in the reaction.…”

Important Green Chemistry and Catalysis: Non‐phosgene Syntheses of Isocyanates – Thermal Cracking Way

“…For example, the methoxycarbonylation of HDA proceeds at around 80 ℃, while that of TDA proceeds at around 180 ℃. Baba et al [25,26] reported that Zn(OAc) 2 was an effective catalyst for methoxycarbonylation of TDA by DMC. A yield as high as 98% of dimethyltoluene-2,4-dicarbamate (TDC) has been obtained at 180 ℃ for 2 h. Besides, Pb(OAc) 2 was also employed for methoxycarbonylation of TDA with DMC.…”

“…Similarly, zinc acetate and its hydrated derivative also showed excellent efficiency and selectivity in the methoxycarbonylation of MDA with DMC. [26,30,31] With a 25∶1 molar ratio of DMC to MDA, a temperature of 180 ℃, and 1 mol% Zn(OAc) 2 •2H 2 O, the desired dicarbamate was formed in 97% yield. Besides, aromatic amine substrates consistently gave high yields (up to 98%) with DMC or DEC using Zn 4 O(OAc) 6 as a catalyst, regardless of the electronic properties of the substituents or the ring substitution pattern.…”

Investigation of the By‐products Formed during the Catalytic Synthesis of 4,4′‐Methylenedimethyldiphenylcarbamate

“…(1)] has drawn a lot of attention recently. [1][2][3][4][5][6][7] Many kinds of by-products including mono-carbamate, N-methylated derivatives and ureas might be formed during the reaction [Eq. (1)], some of which are listed in Figure 1 in order to help identifying the structures of the by-products actually formed.…”

“…4,5 Thus it would be very important to identify the species and structures of the by-products to clarify the reaction mechanism. In this paper, MDC was synthesized by the reaction in Eq.…”