Contributions to the structure of some sulphonyl-benzamidines and -guanidines

Abstract

The solution spectra of some sulphonyl-benzamidines and -guanidines, in conjunction with the weakly acidic nature of these compounds, provide evidence for the predominance of the sulphonylimino-over the sulphonylamino-tautomers. As the iodomethylsulphonyl derivatives show the same structures in chloroform solution as those indicated by their capacity to ring-close in aqueous alkali, assignment of the configuration about the carbonnitrogen double bond has been possible.THE detailed structure of sulphonyl-amidines and -guanidines has received little study despite the doubt regarding the position of the equilibrium between the tautomers (I) and (11). The preliminary considerations of Barber and the empirical U.V. studies of Angyal and Warburton favoured the sulphonylimino-form for (I; R1 = 9-AcNH*C,H,, R2 = Ph, R3 = H), but no definitive studies have been made on the ' linear ' sulphonylamidine and sulphonylguanidine systems. Examination of the few

Formation of 5-aryl-5,6-dihydro-4H-1,2,4-thiadiazine 1,1-dioxides and N-trans-styrylamidines by base treatment of N-(trans-styrylsulfonyl) amidines

“…Water (100 ml) was added to the residue and the mixture was acidified with 3 N HC1. Insoluble solid was collected by filtration, washed with water, air dried, and crystallized from t-PrOAc to afford 8.5 g (76%) of la as white crystals: nmr (CDCI3) 7.84 (broad s, 1, NH), 7.64 (d, 2, J = 15.5 Hz, =CH), 7.45 (m, 5, ArH), 6.92 (d, 2, J = 15.5 Hz, =CH), 6.73 (broad s, 1, NH), 2.16 Other N-(styrylsulfonyl) amidines in Table I were prepared by similar procedures. Reaction of trans -2-nitrostyrylsulfonyl chloride with benzamidine, according to this procedure, failed to afford a solid product lj.…”

“…Evaporation of the solvent gave a yellow oil that formed a salt with ethanolic HC1. The crude salt was triturated with acetone and crystallized to afford 0.25 g (6.5%) of N-(transstyryl)benzamidine hydrochloride (3b): nmr (DMSO-d6) 12.03 (broad s, 1, NH), 10.33 (broad, 2, NH2), 8.25 (d, 1, J = 14.0 Hz, =CH), 8.0-7.1 (m, 10, ArH), 6.95 (d, 1, J = 14.0 Hz, =CH); ir (KBr) ~3050 (broad, NH), 1665 cm'1 (broad, C=N).…”

“…(m, 5, ArH), 7.70 (d, 2, J = 9.0 Hz, ArH), 6.97 (d, 1, J = 14.0 Hz, =CH); ir (KBr) 3020 (broad, NH), 1670 cm'1 (broad, C=N).…”

“…a Unreacted starting material was recovered (18%). 6 Compound 3e was obtained in 49% yield after 30 hr reaction time. c Reaction time was 24 hr.…”