A process for producing an oligomer comprising contacting a dialkyl carbonate and a dihydroxy compound in a reaction zone in the presence of an oligomerization catalyst under oligomerization conditions to form the oligomer wherein the molar ratio of dihydroxy compound to dialkyl carbonate in the reaction zone is at least 2:1.

A process for producing an oligomer comprising contacting a dialkyl carbonate and a dihydroxy compound in a reaction zone in the presence of an oligomerization catalyst under oligomerization conditions to form the oligomer wherein the molar ratio of dihydroxy compound to dialkyl carbonate in the reaction zone is at least 2:1.

A process for producing polycarbonate comprising: a) contacting a dialkyl carbonate with a dihydroxy compound in an oligomerization zone in the presence of an oligomerization catalyst under oligomerization conditions to form a first intermediate; and b) contacting the first intermediate with a diaryl carbonate in a polymerization zone in the presence of a polymerization catalyst under polymerization conditions to produce the polycarbonate wherein the molar ratio of dihydroxy compound to dialkyl carbonate in the oligomerization zone is at least 2:1.

A process for producing polycarbonate comprising: a) contacting a dialkyl carbonate with a dihydroxy compound in an oligomerization zone in the presence of an oligomerization catalyst under oligomerization conditions to form a first intermediate; and b) contacting the first intermediate with a diaryl carbonate in a polymerization zone in the presence of a polymerization catalyst under polymerization conditions to produce the polycarbonate wherein the molar ratio of dihydroxy compound to dialkyl carbonate in the oligomerization zone is at least 2:1.

A process for producing an oligomer comprising contacting a alkylaryl carbonate and a dihydroxy compound in a reaction zone in the presence of an oligomerization catalyst under oligomerization conditions to form the oligomer wherein the molar ratio of dihydroxy compound to alkylaryl carbonate in the reaction zone is at least 2:1.

A process for producing an oligomer comprising contacting a alkylaryl carbonate and a dihydroxy compound in a reaction zone in the presence of an oligomerization catalyst under oligomerization conditions to form the oligomer wherein the molar ratio of dihydroxy compound to alkylaryl carbonate in the reaction zone is at least 2:1.

A process for producing an oligomer comprising contacting a alkylaryl carbonate and a dihydroxy compound in a reaction zone in the presence of an oligomerization catalyst under oligomerization conditions to form the oligomer wherein the molar ratio of dihydroxy compound to alkylaryl carbonate in the reaction zone is at least 2:1.

A process for preparing a diaryl carbonate from a dialkyl carbonate and an aryl alcohol is disclosed. The process takes place in apparatus comprising at least two distillation columns, and at least one of the distillation columns is operated at subatmospheric pressure which is achieved using vacuum equipment.

The present disclosure relates to a recycling method for producing dimethyl carbonate and dimethyl carbonate derivatives. The process is unique in that it produces a by-product that can be re-used in the process as a raw material for repeating the process. For example, when the process is directed to synthesizing dimethyl carbonate, glycerol is used as a starting material. Glycerol is also a by-product produced during formation of dimethyl carbonate, and therefore it can be re-used as starting material to generate more dimethyl carbonate.

A compound represented by a formula [1D] as shown below (wherein R.sup.1A, R.sup.1B, R.sup.2A, R.sup.2B, R.sup.3A and R.sup.3B represent a hydrogen atom, an optionally substituted C.sub.1-6 alkyl group, and the like) is useful as an intermediate for producing a thionucleoside, and the production method of the present invention is useful as a method for producing a thionucleoside.

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