(3aR,6S,7aR)-7a-Chloro-6-methyl-2-(4-nitrophenylsulfonyl)-1,2,3,6,7,7a-hexahydro-3a,6-epoxyisoindole

In the title compound, C15H15ClN2O5S, the tetrahydrofuran ring adopts an envelope conformation with the O atom as the flap. The pyrrolidine ring adopts an envelope conformation with the chlorine-substituted C atom as the flap. In the crystal, two types of C—H⋯O hydrogen bonds generate R 2 2(20) and R 4 4(26) rings, with adjacent rings running parallel to ac plane. Further C—H⋯O hydrogen bonds form a C(6) chain, linking the molecules in the b-axis direction.


Comment
The use of protective groups has been popular in synthetic pathways (Romanski et al., 2012;Chan & White, 2004;Yasushi and Higuchi, 2006;Blanc and Bochet, 2007). Many protective groups have been, developed to block other reactive sites of a molecule like NH, OH, SH, aldehyde etc. They should be easily removable (Greene & Wuts, 1999).
We have been working on intramolecular Diels Alder reaction (IMDAF) of compounds with a furan core using different side chains containing a heteroatom like oxygen, sulfur and nitrogen. Isoindole derivatives have been often synthesized and analyzed in our group using bulky protective groups (Büyükgüngör et al., 2005;Koşar et al., 2006a;Koşar et al., 2006b;Karaarslan et al., 2007;Demircan et al., 2011). Tosyl and mesyl groups have been previously used and reported in a series of sulfonamides (Temel et al., 2012;Temel et al., 2011). We now here report our further finding that cycloadduct, 3 with p-nosyl group was generated at the intermediate via, 2 in aqueous condition without any other solvent system.

Figure 1
Synthesis of the title compound.

Figure 2
The molecular structure of the title compound, with displacement ellipsoids drawn at the 30% probability level.   Part of the crystal structure of the title compound, showing the formation of R 2 2 (10) and R 4 4 (26) rings.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. 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 > 2σ(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.