cis-6-Bromo-4-(1-methyl-1H-indol-3-yl)-10,10a-dihydro-1H,4H-2,9-dioxa-3-azabenz[f]azulene

In the title compound, C20H17BrN2O2, the seven-membered oxepine ring adopts a chair conformation. The indole moiety is essentially planar with a maximum deviation of 0.031 (3)Å. The indole ring system forms a dihedral angle of 21.87 (8)° with the mean plane of the 10-membered heterobicycle. The crystal packing is stabilized by intermolecular C—H⋯O and C—H⋯π interactions.

In the title compound, C 20 H 17 BrN 2 O 2 , the seven-membered oxepine ring adopts a chair conformation. The indole moiety is essentially planar with a maximum deviation of 0.031 (3)Å . The indole ring system forms a dihedral angle of 21.87 (8) with the mean plane of the 10-membered heterobicycle. The crystal packing is stabilized by intermolecular C-HÁ Á ÁO and C-HÁ Á Á interactions.
Cg1and Cg2 are the centroids of the C1-C6 and C15-C20 rings, respectively.  azulene P. Narayanan, K. Sethusankar, K. Ramachandiran and P. T. Perumal Comment 1,3-Dipolar cycloaddition of nitrile oxide is regarded as a useful synthetic method in organic synthesis. The cycloaddition occurs in a stereospecific way to provide 4,5-dihydroisoxazoles (Caramella & Grunanger, 1984). The isoxazoline derivatives are known to exibit interesting biological activities in the agricultural field and possess medicinal properties including antiviral and anti-HIV activities (Ichiba & Scheuer, 1993). Intramolecular nitrile oxide cycloaddition (INOC) reaction offers a powerful strategy to construct carbo-or heterocyclic compounds and many reports on the stereoselective INOC reaction have been published in recent years (Scott et al., 2006). The nitro group is converted into nitrile oxide by Mukaiyama reaction (Mukaiyama & Hoshino, 1960). They successfully prepared five-and six-membered carbo-, oxa-, and thiocyclic compounds and one-pot conversion of nitroalkenes to bicyclic isoxazoles was utilized in some protocols.

cis
The molecular structure of the title compound C 20 H 17 BrN 2 O 2 , is shown at Fig. 1. In the compound, the indole bicycle is essentially planar. The maximum deviation of the atom C7 of the methyl group from the indole bicycle is 0.031 (3)Å.
In the benzene ring of indole moiety, the endo-cyclic angles at C5 and C2 are contracted to 117.8 (2)° and 118.9 (2)°, respectively, while those at C6, C4 and C3 are expanded to 121.9 (2)°, 121.6 (3)° and 121.2 (3)°, respectively. This would appear to be a real effect caused by the fusion of the smaller pyrrole ring to the six-membered benzene ring, and the strain is taken up by the angular distortion rather than by bond-length distortions (Allen, 1981).
Single crystals appeared from the same eluent mixture.

Refinement
All hydrogen atoms were placed in calculated positions with C-H = 0.93-0.98Å and refined in riding model with isotropic displacement parameters: U iso (H) = 1.5 U eq (C) for methyl group and U iso (H) = 1.2 U eq (C) for other groups.  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.