Supplementary Information Insights into conformational and packing features in a series of aryl substituted ethyl-6-methyl-4-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidine- 5-carboxylates. 5 Susanta K. Nayak, a K. N. Venugopala, a Deepak Chopra, b* T. N. Guru Row a a Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 56001, INDIA. b Indian Institute of Science Education and Research, ITI (Gas Rahat Building), Govindpura, Bhopal 462023, INDIA. Fax: 0755-4092392 Tel: 0755-4092321; E-mail: dchopra@iiserbhopal.ac.in 10 Table S1: Melting points and relevant details about the synthesized compounds (PYR 1-8) Compound code Mol. Formulae Mol. Weight Yield (%) M.P ( 0 C) PYRO1 (-o-F) C 14 H 15 FN 2 O 3 278 58 258-260 PYRO2 (-p-F) C 14 H 15 FN 2 O 3 278 57 178-182 PYRO3 (-p-Cl) C 14 H 15 ClN 2 O 3 294 68 210-212 PYRO4 (-p-Br) C 14 H 15 BrN 2 O 3 338 62 231-233 PYRO5 (-p-Me) C 15 H 18 N 2 O 3 274 60 214-216 PYRO6 (-p-OMe) C 15 H 18 N 2 O 4 290 59 202-204 PYRO7 (-m-OMe) C 15 H 18 N 2 O 4 290 60 222-224 PYRO8 (m-(OMe) p-OH) C 15 H 18 N 2 O 5 306 54 186-188 Table S2: Relevant Bond Lengths (Å) and Bond Angles (°). Geometrical Parameter PYRO1 PYRO2A PYRO2B A/B PYRO3 A/B PYRO4 PYRO5 A/B PYRO6 A/B PYRO7 PYRO8 C1-O1 1.230(3) 1.244(2) 1.237(3)/1.236(3) 1.232(2)/1.234(2) 1.232(4) 1.243(2)/1.241(2) 1.243(2)/1.245(2) 1.243(2)) 1.240(2 C1-N1 1.367(2) 1.379(3) 1.375(3)/1.382(4) 1.340(2)/1.337(2) 1.363(6) 1.374(2)/1.370(3) 1.370(2)/1.376(2) 1.373(1) 1.374(3) C1-N2 1.339(2) 1.330(3) 1.333(5)/1.340(4) 1.370(2)/1.373(2) 1.340(4) 1.337(2)/1.334(3) 1.339(2)/1.325(2) 1.326(2) 1.335(3) C5-O2 1.211(2) 1.206(3) 1.220(4)/1.207(4) 1.215(1)/1.208(1) 1.198(6) 1.213(2)/1.207(3) 1.206(2)/1.209(3) 1.203(2) 1.204(2) O3-C6 1.447(2) 1.455(3) 1.511)2)/1.449(2) 1.457(1)/1.456(3) 1.448(5) 1.4621(2)/1.451(3) 1.455(3)/1 .475(3) 1.453(2) 1.462(2) C3-C2 1.345(2) 1.346(3) 1.342(2)/1.344(2) 1.345(2)/1.347(3) 1.3404(7) 1.348(2)/1.351(3) 1.346(2)/1.345(2) 1.342(2) 1.338(3) C2-N1 1.380(2) 1.390(2) 1.390(3)/1.393(3) 1.395(2)1.391(2) 1.391(6) 1.395(2)/1.309(2) 1.393(2)/1.401(2) 1.391(2) 1.398(2) N2-C1-O1 123.5(1) 124.1(2) 123.7(2)/124.4(3) 123.2(1)/123.9(1) 123.8(3) 123.3(2)/124.2(3) 124.0(2)/123.4(2) 123.4(1) 123.2(3) N1-C2-C8 112.8(1) 114.4(2) 112.0(2)/112.8(2) 112.9(2)/112.9(1) 113.05(5) 112.5/(2)113.3(2) 113.2(2)/113.5(2) 113.7(2) 113.7(2) C4-C3-C5 117.9(1) 119.9(1) 119.0(2)/119.69(2) 118.8(2)/119.5(2) 117.8(5) 118.9(2)/119.7(3) 119.4(2)/119.6(2) 118.9(1) 118.9(2) 15 Table S3: Cremer and Pople ring puckering parameters for the six membered tetrahydropyrimidine ring [N1-N2/C1-C4] Compound name Q (Å) Thetha (°) Phi (°) PYRO1 0.430(2) 74.0(3) 171.2(3) PYRO2A 0.430(2) 74.0(3) 171.2(3) PYRO2B (Molecule A/B) 0.355(2)/0.364(3) 72.7(5)/71.2(5) 169.1(5)/169.5(4) PYRO3 (Molecule A/B) 0.343(2)/0.380(2) 108.4(3)/110.0(3) 131.4(3)/132.3(3) PYRO4 0.213(5) 71.0(13) 155.2(14) PYRO5 (Molecule A/B) 0.349(2)/0.380(2) 71.4(3)/70.2(3) 167.5(4)/166.8(4) PYRO6 (Molecule A/B) 0.364(2)/0.359(2) 70.6(3)/72.8(3) 162.1(3)/175.6(4)