title: E- or Z-Selective synthesis of 4-fluorovinyl-1,2,3-triazoles with fluorinated second-generation Julia-Kocienski reagents.
abstract: A highly modular approach to N-substituted 4-(1-fluorovinyl)triazoles is described. In situ desilylation and Cu-catalyzed ligation reaction of TMS-protected α-fluoropropargyl benzothiazole sulfone with aryl, alkyl, and metallocenyl azides furnished second-generation Julia-Kocienski reagents in good to excellent yields. Condensation reactions of these reagents with aldehydes can be tuned to yield E or Z-alkenes selectively. Under mild conditions with DBU as the base, reactions of aldehydes furnished E-alkenes as the major isomer. On the other hand, in condensation reactions with LHMDS as the base and in appropriate solvents, both aldehydes and ketones reacted to yield fluoroalkenes with Z-selectivity. Stereochemical assignment of E/Z olefins obtained in the reaction of a ketone with two Julia reagents was performed via X-ray crystallographic analysis and comparisons of NMR data. The method allows efficient and ready diversification of the N1-substituent and substituents at the double bond.
authors.affiliation: Department of Chemistry, The City College and The City University of New York, 160 Convent Avenue, New York, NY 10031, USA.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kumar
authors.forename: Govindra
authors.initials: G
authors.lastname: Singh
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Todaro
authors.forename: Lijia
authors.initials: L
authors.lastname: Yang
authors.forename: Barbara
authors.initials: B
authors.lastname: Zajc
mesh_terms: D060326:Chemistry Techniques, Synthetic; D054879:Halogenation; D007202:Indicators and Reagents / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism; D014230:Triazoles / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D007202:Indicators and Reagents; D014230:Triazoles