Dimethyl carbonate butylamine with

The occurrence of nucleophilic catalysis has been reported in the reactions of dimethyl carbonate with carboxylic acids and indoles under the presence of tertiary amines such as l,8-diazabicyc/o[5.4.0]undec-7-ene (DBU) and DABCO. However, it remained unclear why tertiary amines such as Af-methyl-morpholine and tertiary butylamine revealed almost zero catalytic efficiency. 

When Schiff s bases (242), derived from ketones and tm-butylamine, were reacted with dimethyl methoxymethylenemalonate in diphenyl ether at 80-130°C for 1-15 hr, then at 190-250°C for 1-3 hr, 2-hydroxy-3-pyridinecarboxylates (243) were obtained by a one-pot procedure. In the first step of the reaction, the beta-carbon of the enamine moiety was involved instead of the amino group (89JHC773). 

The intermediates M1-M5 were prepared according to the procedure described in Chap. 2. IIJ could be obtained by the treatment of 0,0-dimethyl l-(substimted phenoxyacetoxy)aIkylphosphonates IC with an excess of t-butylamine. In this reaction, t-butylamine could selectively and quantitatively eliminate one methyl from two MeO groups which attached to phosphorus in IC. The possible reaction mechanism for forming r-butylaminium 0-methyl phosphonate IIJ is outlined in Scheme 3.13. t-Butylamine first attacks the methyl carbon, forming intermediateiV-t-butyl-A-methyl ammonium salt, which is then deprotonated by another f-butyl-amine to form t-butylaminium and iV-methyl-Al-r-butylamine. Finally, the cation of t-butylaminium binds with the anion of phosphonate to form the IIJ. 

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