Ethyldiazoacetate reacts as a carbene precursor in presence of copper exchanged bentonite. Reaction with excess nitrile gave oxazole derivatives. Their formation is explained by intramolecular 1,5-cyclisation of alkoxycarbonyl substituted nitrile ylide intermediate. Scheme 2 Scheme 3 JOURNAL OF CHEMICAL RESEARCH 2012 151 5-Ethoxy-2-isopropyl-1,3-oxazole (7c): 17 Yield: 67%, translucent liquid, b.p. 85 °C/20 mmHg. 1 H NMR: δ = 1.30 (d,(CH 3 ) 2 CH, 6H, 3 J H-H = 7.0), 1.41 (t, OCH 2 -CH 3 , 3H, 3 J H-H = 7.0), 2.94 (m, 1H), 4.08 (q, OCH 2 -CH 3 , 2H, 3 J H-H = 7.0), 5.94 (s, 1H). 13 C NMR: δ = 14.4, 20.1, 28.3, 67.6, 98.2, 159.25, 159.5; HRMS, m/z (found/calcd): 155.0943/ 155. 0946 (M+ . , C 8 H 13 N O 2 ). 2-Benzyl-5-ethoxy-1,3-oxazole (7d): 18 Yield: 80%, white solid, b.p. 65-70 °C/0.02 mmHg. 1 H NMR: δ = 1.38 (t, OCH 2 -CH 3 , 3H, 3 J H-H = 7.0), 3.97 (s, Ph-CH 2 , 2H), 4.05 (q, OCH 2 -CH 3 , 2H, 3 J H-H = 7.0), 5.97 (s, 1H), 7.22-7.35 (m, 5H). 13 C NMR: δ = 14.4, 34.8, 67.8, 98.9, 126.9, 128.6, 128.7, 135.6, 153.6, 159.7; HRMS, m/z (found/ calcd): 203.0954 / 203.0946 (M+ . , C 12 H 13 N O 2 ). Ethyl acetamidoacetate (8a): 19 Yield: 10%, hygroscopic white solid, b.p. 65-70 °C/0.02 mmHg. 1 H NMR: δ = 1.28 (t, OCH 2 -CH 3 , 3H, 3 J H-H = 7.1), 2.04 (s, 3H), 3.99 (d, 2H, 3 J H-H =5.5), 4.19 (q, 2H, 3 J H-H = 7.1), 7.23 (br s, 1H, NH). 13 C NMR: δ = 13.6, 22.5, 41.2, 61.2 171.0, 170.1. Ethyl 2-(propionamido)acetate (8b): Yield: 5%, light yellow liquid, b.p. 100 °C/0,1 mmHg. 1 H NMR: δ = 1.14 (t, CH 3 -CH 2 , 3H, 3 J H-H = 7.2), 1.29 (t, OCH 2 -CH 3 , 3H, 3 J H-H = 7.1), 2.34 (q, 2H, 3 J H-H = 7.3), 4.02 (d, 2H, 3 J H-H =5.2), 4.19 (q, OCH 2 -CH 3 , 2H, 3 J H-H = 7.1), 6.28 (br s, 1H, NH). 13 C NMR: δ = 9.0, 14.1, 26.0, 48.0, 61.2, 169.5, 174.3. HRMS, m/z (found/calcd): 159.0902 / 159.0895 (M+ . , C 7 H 13 N O 3 ).