| 摘要 |
This invention is directed to a process for the synthesis of 2,2-dialkoxy cyclic ortho esters derived from lactones which comprises reacting trialkyl orthoformate with boron trifluoride to give dialkoxymethylium tetrafluoroborate; reacting dialkoxymethylium tetrafluoroborate with a lactone to give the corresponding O-alkyllactonium tetrafluoroborate; and reacting the O-alkyllactonium tetrafluoroborate with an alkoxide, or alternatively with an alkanol in the presence of a base; wherein the first two steps of the process of the invention are conducted in the absence of solvents, other than the reactants themselves. The third step may also optionally be run without solvents. The invention is also directed to the preparation of the O-alkyllactonium tetrafluoroborate in one reaction vessel; that is, the boron trifluoride is added to the trialkyl orthoformate and the lactone in a single reaction vessel. As the intermediate dialkoxymethylium tetrafluoroborate is formed, it reacts in situ with the lactone in the reaction mixture, thus avoiding the additional steps of separating the dialkoxymethylium tetrafluoroborate and then reacting it with the lactone in a separate step and vessel.
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