Side-chain electrophilic aromatic substitution in 2-alkyloxa- and 2-alkylthiazolines initiated via σ-complex formation with super-electrophilic DNBF: a model proinsecticideElectronic supplementary information (ESI) available: the ABX analysis of the CH2-α and H2 proton region of the adduct 5-Oa. See http://www.rsc.org/suppdata/p2/b2/b201045n/
A 1H and 13C NMR study of the reaction of a series of 2-alkyloxa- and 2-alkylthiazolines 3-Xaâc with 4,6-dinitrobenzofuroxan (DNBF) in DMSO revealed the formation of the C-bonded Ï-adducts 5-Xaâc. Product isolation following addition of Et3N or KOAc, afforded the Et3NH+ or K+ salts of the DNBF adducts, respectively. The NMR results showed conclusively that coupling of the DNBF moiety with the oxazoline or thiazoline heterocycle occurred at the α position of the 2-alkyl side-chain. A most reasonable mechanism for this coupling involves initial formation of a transient N-bonded adduct between the N-heterocycle and DNBF, which subsequently rearranges through the action of base to the C-bonded adduct as the product of thermodynamic control. The relevance of this work to oxa- and thiazoline-based proinsecticide is emphasized.
Straightforward microwave-assisted synthesis of 2-thiazolines using Lawesson's reagent under solvent-free conditions
作者:Julio A. Seijas、M. Pilar Vázquez-Tato、José Crecente-Campo
DOI:10.1016/j.tet.2008.07.027
日期:2008.9
2-Thiazolines are synthesized from carboxylic acids and 1,2-aminoalcohols in the presence of Lawesson's reagent under solventless conditions. The developed method is valid for either substituted or unsubstituted aminoalcohols and a wide variety of aromatic, heteroaromatic and aliphatic carboxylic acids; thus it constitutes a general synthetic method for these kinds of compounds. The role of Lawesson's