Crystal structure of 2,3,6a,9-tetrahydro-1H-6,9-methanopyrrolo [2,1-i][2,1]benzisothiazol-10(6H)-one 5,5-dioxide, C11H13NO3S

Abstract

C 11 H 13 NO 3 S, monoclinic, P12 1 /c1(no. 14), a =11.564(2) Å, b =16.574(2) Å, c =12.152(2) Å, b =116.832(6)°, V =2078.4 Å 3 , Z =8,R(F) =0.034, wR ref (F 2 ) =0.094, T =173 K. N-[3-(2-hydroxyphenyl)propyl]ethylenesulfonamide (774 mg, 3.2 mmol) in toluene (20 ml) was slowly added over aperiod of 50 min (syringe pump) to acold (−78°C) solution of diacetoxyiodobenzene (1.3 g, 4.2 mmol, 1.3 eq.) and trifluoroacetic acid (712 mg, 6.3 mmol, 1.9 eq.) in toluene (20 ml) and dichloromethane (2 ml). At the end of the addition, the solution had become light yellow. The reaction mixture was stirred at −78°C for 20 min. and then slowly warmed to room temperature. Stirring was continued for another 30 min, then the mixture was heated to 100°C for 3 hours to promote Diel-Alder cyclization of the primary product. The progress of the reaction was monitored by 1 HNMR. Upon completion, the solution was concentrated and the residue was dried under high vacuum. Chromatography (50 %E tOAc/hexanes) gave 276 mg (1.16 mmol, 36 %) of pure 2,3,6a,9-tetrahydro-1H-6,9-methanopyrrolo[2,1-i][2,1]benzisothiazol-10(6H)-one-5,5-dioxide as an off-white powder. Acrystal suitable for Xray diffractometry was obtained by slow evaporation (two weeks) of asolution in (1:4, v/v)dichloromethane/hexanes. Source of material Experimental detailsAll hydrogen atoms were included in calculated positions with coordinates riding on their parent atom, with U iso(H) =1 .2 U eq (C). DiscussionThe title compound is an intermediate in an ongoing synthetic study on Himandrine and related alkaloids [1,2]. The lattice contains two crystallographically independent molecules in the asymmetric unit, however there are no significant geometric differences between the two molecules. The two independent molecules pack as dimers connected by two seperate C−H···O interactions (C8−H8···O27 and C23−H23B···O10). Any differences between the two independent molecules are very subtle, with no difference in bond lengths greater than 0.005 Å and no bond angle differences greater than 1.2°. The same can be said for any torsion angle differences, with none larger than 7.1°. Most of the significant differences occur around between the N12−C2− C3−C8−S9 and N28−C18−C19−C24−S25 fused-ring moieties.