4-Chloro-2-((1R)-1-{[(R)-(2-chlorophenyl)(cyclopentyl)methyl]amino}ethyl)phenol

The title compound, C20H23Cl2NO, was prepared by condensation of (R)-1-(2-chlorophenyl)-1-cyclopentylmethanamine with 1-(5-chloro-2-hydroxyphenyl)ethanone, resulting in the formation of a new chiral center. The structural analysis confirms the absolute configuration of the title compound and the formation of the (R,R) diastereoisomer. There is an intramolecular O—H⋯N hydrogen bond which stabilizes the conformation of the molecule. The molecules are linked to each other through weak C—H⋯π interactions.

The title compound, C 20 H 23 Cl 2 NO, was prepared by condensation of (R)-1-(2-chlorophenyl)-1-cyclopentylmethanamine with 1-(5-chloro-2-hydroxyphenyl)ethanone, resulting in the formation of a new chiral center. The structural analysis confirms the absolute configuration of the title compound and the formation of the (R,R) diastereoisomer. There is an intramolecular O-HÁ Á ÁN hydrogen bond which stabilizes the conformation of the molecule. The molecules are linked to each other through weak C-HÁ Á Á interactions.

Comment
The synthesis of enantiopure amine alcohols with a variety of functionalities is an important subject of research because this class of compounds has found widespread application in biological systems showing pharmacological activity. These compounds are used as resolving agents, chiral bases and auxiliaries in asymmetric synthesis (Cimarelli et al.,2002), and most have been derived from new readily available natural products (Ager et al.,1996). Chiral aminophenols, which are similar to aminoalcohols, are important building blocks in organic synthesis, and have attracted increasing attention in recent years owing to their effects in asymmetric synthesis and asymmetric induction (Cimarelli et al.,2001;Palmieri, 1999Palmieri, , 2000Xu & Pu, 2004;Berrisford et al., 1995;Cimarelli & Palmieri, 1998;Hayase et al., 1997;Nakano et al.,1997;Soai et al., 1992;Watanabe et al., 1991).
As part of our continuing studies of chiral aminophenols, we have established the molecular structure of the title compound which was intially synthesized to test its asymmetric catalytic activity. The compound has been prepared by conventional condensation of (R)-1-(2-chlorophenyl)-1-cyclopentylmethanamine with 1-(5-chloro-2-hydroxyphenyl)ethanone, resulting in the formation of a new chiral center as shown in Fig. 1.
The structural analyses confirms the absolute configuration of the title compound and the formation of the (R,R) diastereoisomer. There is an intramolecular O-H···N hydrogen bond which stabilizes the conformation of the molecule. The molecules are linked to each other through weak C-H···π interaction involving the C15-C20 benzene ring (Table 1).

Experimental
The title compound were prepared according to the procedure of Yang et al.(2005). (R)-1-(2-chlorophenyl)-1-cyclopentylmethanamine (0.9 mmol) and 1-(5-chloro-2-hydroxyphenyl)ethanone (0.9 mmol) were dissolved in methanol (10 ml) and reacted at room temperature for 48 h. After removal of the solvent, NaBH 4 (4.5 mmol) was added to the solution in THF/ethanol (1:1 v/v, 20 ml) and stirred at 273 K until the solution became colourless. The solvent was then removed under reduced pressure. Water (10 ml)was added to the residue and 1 N HCl was added dropwise until hydrogen production ceased. The mixture was neutralized with aqueous Na 2 CO 3 , then extracted with CHCl 3, and the organic layer was dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure. Further purification was carried out by thin-layer silicagel chromatography (chloroform) to give a colourless solid (yield 83.5%). Crystals of (I) were grown from a n-hexane.