Crystal structure of ethyl 5-chloro-2-indolecarboxylate, C11H10ClNO2

Abstract

Source of materialThe title compound was prepared following the reported procedure [1]. In a typical experiment 0.2 g (yield 89%) of the title compound was obtained. The single crystals were obtained by slow evaporation from an ethanol solution at room temperature. Experimental detailsHydrogen atoms bonded to carbon were positioned geometrically, with C-H = 0.95 to 0.99 Å, and constrained to ride on their parent atoms, with U iso (H) =1.2U eq (C). Positional parameters and the U iso value of the hydrogen atom H1N were refined freely. DiscussionThe indole moiety is a heterocycle found in a large array of natural products and pharmaceuticals possessing anti-allergic [2], central-nervous-system depressant [3], muscle relaxant [4], and anti-cancer [5,6] properties. Consequently, synthetic approaches toward indoles have long been a topic of fundamental interest to organic and medicinal chemists [7,8]. The Fischer indole synthesis is the most widely used method for the preparation of indole derivatives [9,10]. The crystal structure of methyl indole-3-carboxylate [11], as well as the structures of some esters of indole-2-carboxylic acid are known [12][13][14]. The title crystal structure is built by the C 11 H 10 ClNO 2 molecules, in which all bond lengths and angles are in normal ranges. The finding of a nearly planar molecule is in good agreement with the structure of methyl 5-chloro-1H-indole-2-carboxylate [15]. An examination of the deviations from the least-squares planes through individual rings shows that rings A (N1/C1/C2/C3/C8) and B (C3-C8) are each planar. The indole ring system is planar, with a puckering amplitude Q = 0.0069 Å [16]. The mean plane of the methoxy carbonyl group is s slightly twisted with a dihedral angle of 2.06(15)°with respect to the indole ring system. Intermolecular N-H···O hydrogen bonds between C=O and N1-H1N link the molecules, forming centrosymmetric dimers.