title: Two novel 1,2,4,5-tetrazines that participate in inverse electron demand Diels-Alder reactions with an unexpected regioselectivity.
abstract: [reaction: see text] Two new unsymmetrical 1,2,4,5-tetrazines, 3-methylsulfinyl-6-methylthio-1,2,4,5-tetrazine (4) and 3-(benzyloxycarbonyl)amino-6-methylsulfinyl-1,2,4,5-tetrazine (5), were prepared, and the scope of their participation in intermolecular inverse electron demand Diels-Alder reactions was defined. As anticipated, sulfoxides 4 and 5 (4 > 5) display a reactivity that is substantially greater than that of their corresponding sulfides (2 and 3), being derived from their enhanced electron-deficient character and resulting in a wider range of potential dienophile choices or the use of milder reaction conditions. The cycloaddition reactions were expectedly regioselective, typically producing a single cycloadduct, ensuring their synthetic utility, but both were found to proceed with a regioselectivity opposite what would be anticipated and complementary to that observed with 2 and 3.
authors.affiliation: Department of Chemistry and Skaggs Institute for Chemical Biology, Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
authors.forename: Akiyuki
authors.initials: A
authors.lastname: Hamasaki
authors.forename: Richard
authors.initials: R
authors.lastname: Ducray
authors.forename: Dale L
authors.initials: DL
authors.lastname: Boger
mesh_terms: D001391:Azo Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D004583:Electrons; D015394:Molecular Structure
chemical_list: D001391:Azo Compounds