Why is the reaction of ethyl (2-cyanoacetyl)carbamate with ethyl orthoformate highly stereoselective?

Kinetic and mechanistic studies of NEt3-catalyzed intramolecular aminolysis of carbamate

The mechanism of the NEt 3-catalyzed intramolecular aminolysis of Z- 1 in acetonitrile or aqueous acetonitrile solutions is suggested to involve rate-determining collapse of T (+/-) through simultaneous H-abstraction and ethoxide expulsion of E2 process. The evidence for that includes the primary isotope effect of k H/ k D = 1.66 in acetonitrile, general-base catalysis in aqueous buffer solutions, salt effect, and the proposed water-stabilized rate-determining transition states (TS1 and TS2) in the water-titration experiments.

A multi-component reaction to 5-cyanouracils: Synthesis and mechanistic study

Acetonitrile as a solvent, excess of primary amines as general bases, and a reflux condition make the multi-component reactions of (2-cyanoacetyl) carbamate 1, ethyl orthoformate, and primary amines form 5-cyanouracils 4a-c feasibly. Mechanistic studies of the multi-component reaction were carried out by proton NMR spectrometer. Acetonitrile as a solvent makes the reaction of 1 with ethyl orthoformate produce E-ethyl (2-cyano-3-ethoxyacryloyl) carbamate E-2 without a catalyst of acetic anhydride. The reactions of E-2 with primary amines produce the corresponding Z-3a-c as the only stable isomers eventually in CDCl3 or CD3CN. General-base-catalyzed intramolecular cyclizations of Z-3a-c at a reflux condition in CD3CN generated the corresponding 5-cyanouracils 4a-c.