Reaction of ethyl (2-cyanoacetyl)carbamate (1) with ethyl orthoformate in the presence of acetic anhydride is highly stereoselective and only E-ethyl (2-cyano-3-ethoxyacryloyl)carbamate (E-2) is isolated. The reaction is thermodynamic control and the product population depends on relative stability of E-2 and Z-2. Forty percent of E-2 was isomerized to Z-2 after 2 hr irradiation at 254 nm. All the Z-2 is isomerized back to E-2 spontaneously with Ea = 19.6 kcal/mole. Relative stability of E-2 and Z-2 is studied by analysis of second-order perturbation energies of the donor-acceptor interactions using the NBO method at level of HF/6-311++G (3df,3pd)//B3LYP/6-31+G*. Very high transelectron delocalization through lone pair of ethoxy oxygen, C=C double bond, and C=O double bond in E-2 is the key point why the reaction of 1 with ethyl orthoformate and acetic anhydride is highly stereoselective. This is an abstract of a paper presented at the 229th ACS National Meeting (San Diego, CA 3/13-17/2005).
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)