3-Chloro-4-dimethylamino-5-[(1R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy]furan-2(5H)-one

The title compound, C16H26ClNO3 contains one almost planar furanone ring [maximum deviation of 0.021 (2) Å for the O atom] with a stereogenic center (S) and one cyclohexane ring which displays a chair conformation and has three stereogenic centers [S at the C atom bearing the isopropyl group, R at the C atom attached to the O atom and R at the C atom bearing the methyl group].

The title compound, C 16 H 26 ClNO 3 contains one almost planar furanone ring [maximum deviation of 0.021 (2) Å for the O atom] with a stereogenic center (S) and one cyclohexane ring which displays a chair conformation and has three stereogenic centers [S at the C atom bearing the isopropyl group, R at the C atom attached to the O atom and R at the C atom bearing the methyl group].
In the title compound ( Fig. 1), the cyclohexane ring displays a chair conformation and has three stereogenic centers (C2(S), C3(R), C5(R)), and the planar core structure subunit, the furanone ring exhibits a C16(S) center with a maximum deviation of 0.021 (2) Å of O2 from the mean plane of the five atoms defining the plane, r.m.s deviation is 0.0158 Å.
At the same time, N1 is only 0.034 (5) Å from the furanone ring plane. This is one manifestation of the extensive conjugation of the N1 lone pair, the C13═C14 double bond and the C15 carbonyl bond. The geometrical consequence is a shortening of the N1-C13 bond to an value of 1.331 (3) Å, which might be compared with the average value of 1.355 (14) Å for the C-N bond in C═C-N-(C) 2 system (Orpen et al., 1989;Gawronski et al., 1997). The shortening of the N1-C13 bond is accompanied by the lengthening of the formally C13═C14 double bond to an value of 1.354 (3) Å, as compared with the value of 1.323 (13) Å quoted for cyclopentene and with 1.340 (13) Å in conjugated systems (Orpen et al., 1989).
And the most striking geometrical change due to conjugation is found in the furanone ring. Comparison with the non-fused furanones which contain oxygen function at C(4) (22 observations subtracted from the Cambridge Structural Database 14) (Allen, 2002) reveals significant shortening of the formally single C(sp 2 )-C(sp 2 ) bond to an value of 1.428 (4) Å and simultaneous lengthening of the C(carbonyl)-O bond to an value of 1.373 (3) Å. In non-fused furanones the two bonds have the mean values of 1.466 (26) Å and 1.362 (16) Å, respectively (Allen et al., 1987;Gawronski et al., 1997). This might indicate that the essential part of the electron delocalization is concentrated in the N1, C13, C14, C15 and O3 region, and takes place at the expense of delocalization within the ester function.

Refinement
All H atoms were positioned in calculated positions (C-H = 0.96 Å or 0.97 Å or 0.98 Å) and were refined using a riding model, with U iso (H) = 1.2 U eq (C) for methylene or methine H atoms and U iso (H) = 1.5 U eq (C) for methyl H atoms. Fig. 1. The molecular structure of the title compound. Displacement ellipsoids drawn at the 30% probability level, hydrogen atoms have been omitted for clarity. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.