1′,1′′-Dimethyl-4′-phenyldispiro[11H-indeno[1,2-b]quinoxaline-11,2′-pyrrolidine-3′,3′′-piperidin]-4′′-one

In the title compound, C30H28N4O, the central pyrrolidine ring adopts an envelope conformation with the CH2 C atom as the flap. The quinoxaline and indene ring systems are planar, with r.m.s. deviations of 0.0165 and 0.0181 Å, respectively. The pyrrolidine ring mean plane forms dihedral angles of 88.84 (1) and 86.14 (1)° with the quinoxaline and indene ring systems, respectively. A weak intramolecular C—H⋯N interaction is observed. In the crystal, C—H⋯O interactions lead to helical supramolecular chains along the b axis having a C(9) motif.

In the title compound, C 30 H 28 N 4 O, the central pyrrolidine ring adopts an envelope conformation with the CH 2 C atom as the flap. The quinoxaline and indene ring systems are planar, with r.m.s. deviations of 0.0165 and 0.0181 Å , respectively. The pyrrolidine ring mean plane forms dihedral angles of 88.84 (1) and 86.14 (1) with the quinoxaline and indene ring systems, respectively. A weak intramolecular C-HÁ Á ÁN interaction is observed. In the crystal, C-HÁ Á ÁO interactions lead to helical supramolecular chains along the b axis having a C(9) motif.

Comment
Spiro compounds are a particular class of naturally occurring substances characterized by highly pronounced biological properties (Kobayashi et al., 1991;James et al., 1991). Pyrrolidine derivatives are found to have anti-convulsant, antimicrobial and anti-fungal activities against various pathogens (Amal Raj et al., 2003). Our interest in preparing pharmacologically active pyrrolidines led us to the title compound, and we have undertaken X-ray crystal structure determination in order to establish its conformation.
The sum of bond angles around N1 (341.8°) and N2 (339.7°) indicate the atoms N1 and N2 are each in a trigonal geometry. A weak intramolecular C-H···N interaction is observed (Table 1).
In the crystal structure, a C-H···O interaction leads to helical chains generating a C 2 2 (9) motif (Bernstein et al., 1995).

Experimental
enediamine (1 mmol) and sarcosine (1 mmol) in methanol was refluxed for 3-4 h. After completion of the reaction, as indicated by TLC, the reaction mixture was poured into cold water. The solid precipitate obtained was filtered and dried.
The product was purified by column chromatography using petroleum ether:ethylacetate mixture (90:10 v/v). Suitable crystals for the single crystal X-ray studies were obtained by recrystallizing the product from methanol. Yield: 45%, M.pt: 510-511 K.

Refinement
H atoms were placed at calculated positions and allowed to ride on their carrier atoms with C-H = 0.93-0.98Å. U iso = 1.2U eq (C) for CH 2 and CH groups and U iso = 1.5U eq (C) for CH 3 groups. The reflections (1 0 0)     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 > 2sigma(F 2 ) is used only for calculating R-factors (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.