ChemInform Abstract: Stereoisomerism in the Adducts of Appel′s Salt with Activated Methylenes.

Abstract

stereochemistry stereochemistry (general, optical resolution) O 0030 -043Stereoisomerism in the Adducts of Appel's Salt with Activated Methylenes.-Reaction of Appel's salt (I) with activated methylene compounds provides adducts, of which some of them display an interesting equilibrium between two stereoisomers, e.g. (V) and (VI), which have either a S···O or a S···N interaction. -(D'HOOGE, B.; DEHAEN, W.; Bull. Soc.

Synthesis of 2-Mercapto-(2-Oxoindolin-3-Ylidene)Acetonitriles from 3-(4-Chloro-5H-1,2,3-Dithiazol-5-Ylidene)Indolin-2-ones

“…The stereoselectivity depends on steric hindrance between the chlorine atom at the C4 position of the dithiazole ring, and the oxygen atom on the carbonyl lactame of the indolin-2-one moiety. Additionally, an attractive interaction, already described by Rees et al, could also be established between this oxygen atom and the sulfur atom at the S1 position of the dithiazole moiety, in light of the mesomer forms ( Figure 3 ) [ 45 , 46 , 47 , 48 , 49 , 50 ].…”

“…It is well known that the reactive 5-chlorine atom of 4,5-dichloro-1,2,3-dithiazolium chloride ( Scheme 1 , 1 ) can be displaced by a variety of nucleophiles, such as primary aromatic amines, or phenols, allowing access to N -heteroimino-1,2,3-dithiazole derivatives ( Scheme 1 , Path a) [ 36 , 37 , 38 , 39 , 40 ]. Several studies described the reactivity of Appel’s salt with active methylene compounds, using mainly malononitrile, tetracyanoethylene oxide (TCNEO), halo-substituted malononitriles and dimethylsulfonium dicyano-methylide, and malonate to afford 5-alkylidene-4-chloro-5 H -1,2,3-dithiazole derivatives ( Scheme 1 , Path b) [ 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ].…”

“…From the 1 H-NMR spectral data displayed, with only one set of aromatic signals in each case, it appeared that only one stereoisomer of each 3-(1,2,3-dithiazol-5-ylidene)indololin-2-one derivative ( Table 1 , 3a – 3d ) was obtained. According to the work of Jeon et al on several alpha-carbonylated 5-alkylidene-1,2,3-dithiazoles, we assumed that the ( Z )-stereoisomers were obtained [ 45 , 46 , 47 , 48 , 49 , 50 ]. The stereoselectivity depends on steric hindrance between the chlorine atom at the C4 position of the dithiazole ring, and the oxygen atom on the carbonyl lactame of the indolin-2-one moiety.…”