3Coumarin derivatives are a useful component for developing new materials, such as fluorescence materials and laser dyes; non-linear optical materials and reagents; photorefractive materials; photoresistors; intermediates for drug synthesis; analytical reagents, etc. 1,2Although the fluorescence of the coumarin, itself, is weak, the introduction of a substituent group into coumarin increases the fluorescence intensity. Recently, we reported the synthesis and fluorescence properties of 7-(diethylamino)coumarin derivatives as fluorophores accessible for analytical purposes in the fields of analytical and biological chemistry. 3 The crystal structures of 7-(diethylamino)coumarin,and 7-(diethylamino)-3-(4-ethoxycarbonylthiazol-2-yl)coumarin 5 have been reported. We now report on the crystal structure of 1 with the aim to contribute to a deeper understanding of the substituent effect at the 3-position of 7-(diethylamino)coumarin (Fig. 1) on the structure and crystal packing.Compound (1) was synthesized by the reaction of 7-(diethylamino)coumarin-3-calbaldehyde and bromoacetaldehyde in DMF as reported in a previous paper.3 The spectral data of 1 are as follows: mp 143 -144 C, Table 1. The H atoms were positioned with the idealized geometry, and were refined to be isotropic (Uiso(H) = 1.2Ueq(C)) using a riding model with C-H = 0.95 Å for aromatic H atoms, C-H = 0.98 Å for methyl H atoms, and 2018 © The Japan Society for Analytical Chemistry Crystal Structure of 7-(Diethylamino)-3-(2-oxazolyl)coumarinKanji KUBO,* † Taisuke MATSUMOTO,** and Haruko TAKECHI*** The structure of 7-(diethylamino)-3-(2-oxazolyl)coumarin (1) was determined by X-ray crystallography. It crystallizes in the space group C2/c (#15) with cell parameters a = 19.168(5)Å, b = 13.233(3)Å, c = 13.141(3)Å, β = 121.6625(9) , Z = 8, and V = 2837.1(12)Å 3 . The R1 (I > 2σ(I )) and wR2 (all data) values are 0.0603 and 0.1797, respectively. The coumarin ring of 1 makes an angle of 26.6(1) with the oxazole ring. Intermolecular C-H···O, C-H···N, C-H···π, and π···π interactions were observed in the crystal lattice.