title: Inverse neighboring group participation: explanation of an unusual S→N alkyl migration of isothiuronium salts containing a lactone group.
abstract: A detailed experimental and DFT study of the S to N alkyl migration of substituted S-(1(3H)-isobenzofuranon-3-yl)isothiuronium bromide to N,N'-dimethyl-N-(3-oxo-1,3-dihydro-2-benzofuran-1-yl)thiourea provided evidence for the existence of an unusual double displacement mechanism involving two consecutive back-side S(N)2 reactions where a carboxylate anion has a crucial role both as a leaving group as well as an internal nucleophile. The thiazetidine zwitterionic species that is involved in this mechanism as an intermediate was characterized by infrared multiphoton dissociation spectroscopy and was trapped with methyl iodide. It was found that the intermediate has a structure of a free ion pair. The double-displacement mechanism can be considered as a new type of inverse lactone neighboring group participation.
authors.affiliation: Faculty of Chemical Technology, Institute of Organic Chemistry and Technology, University of Pardubice, Studentská 573, CZ-532 10 Pardubice, The Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Váňa
authors.forename: Miloš
authors.initials: M
authors.lastname: Sedlák
authors.forename: Richard
authors.initials: R
authors.lastname: Kammel
authors.forename: Jana
authors.initials: J
authors.lastname: Roithová
authors.forename: Anton
authors.initials: A
authors.lastname: Škríba
authors.forename: Juraj
authors.initials: J
authors.lastname: Jašík
authors.forename: Jiří
authors.initials: J
authors.lastname: Hanusek
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D002384:Catalysis; D007550:Isothiuronium / Q000138:chemical synthesis* / Q000737:chemistry; D007783:Lactones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013055:Spectrophotometry, Infrared; D013455:Sulfur / Q000737:chemistry*
chemical_list: D000473:Alkanes; D007783:Lactones; D007550:Isothiuronium; D013455:Sulfur; D009584:Nitrogen