Novel substituted 1,2-oxathietanes from competing cyclizations of 2-chloroethyl sulfoxide precursors. Observation of vinylogous 1,4-halogen participation in 1,2-oxathietane generation

• Published in: Journal of organic chemistry Vol. 51; no. 11; pp. 2116 - 2122
• Main Authors: Lown, J. William, Koganty, R. Rao, Naghipur, Ali
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 01.05.1986; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Exact sciences and technology; Kinetics and mechanisms; Organic chemistry; Physical Sciences; Reactivity and mechanisms; Science & Technology; Oxygen sulfur heterocycle; Four membered ring; Aliphatic compound; Nitrosoureas; Benzaldehyde; Compounds; Cycloreversion; Diazotization; Chlorocarbon; Styrene; Aminosulfoxide; Benzenic compound; Chemical decomposition; Aqueous solution; Ethylenic compound
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo00361a035

Spontaneous ambient temperature decomposition of 1-[2-[(2-chloroethyl)sulfinyl]-threo-1,2-diphenylethyl]-3-tert-butyl-1-nitrosourea in aqueous buffer (pH 7.0) affords fragmentation products corresponding to the formation of 1,2-oxathietane and trans-3,4-diphenyl-1,2-oxathietane. The former is formed in a reaction involving 1,4-chlorine participation with migration of chlorine over three bonds, substitution, and concomitant formation of (E)-1-chlorostilbene. That the halogen is involved in a tightly bound intramolecular reaction is corroborated by the lack of exchange of chlorine in the presence of excess bromide ion. Aqueous diazotizations of 2-[(2-bromoethyl)thio]-1,2-threo-diphenylethylamine hydrobromide and 2-[(2-bromoethyl)sulfinyl]-1-phenylethylamine hydrobromide afford among their products of controlled decomposition, (Z)-1-bromostilbene and (E)- and (Z)-2-bromostyrenes, respectively. These examples confirm the tightly controlled nature of the 1,4-halogen-transfer process. Aqueous decomposition of sulfinylamine precursors, which are not subject to steric hindrance at the carbon .alpha. to the sulfinyl group, e.g., following diazotization of 2-[(2-chloroethyl)sulfinyl]-1-phenylethylamine hydrochloride, affords fragmentation products corresponding to the participation of three separate pathways. These involve the formation of 4-phenyl-1,2-oxathietane, 1,2-oxathietane, and 4-phenyl-1,2,3-oxadiazoline, respectively. These reactions provide further examples of 1,4-halogen participation with migration resulting in conformationally controlled formation of (E)- and (Z)-2-chlorostyrenes from the chloro precursor and (E)- and (Z)-2-bromostyrenes from the corresponding bromo compound.