[reaction: see text] A new allylstannane reagent on non-cross-linked polystyrene was developed for the first time. This support differs markedly from standard cross-linked polymers because it is completely soluble in organic solvents; moreover, the reactions can be conveniently monitored directly by standard 1H NMR methods. The allylstannane underwent a free radical reaction with an alkyl halide to form a new allyl appendage. Tin byproducts can be easily recovered from cold methanol as white crystalline solids.
Introduction of a halogen (F, Cl, Br, I) or a chalcogen (O, S, Se, Te) via the intermediacy of an aryllithium or hetaryllithium is reviewed. Representative examples are presented to demonstrate the range of substituted aromatic compounds accessible via formation of the lithio-intermediate followed by treatment with an appropriate derivatizing agent. Where possible, the merits and the limitations of the various reagents utilized for introduction of a specific halogen or chalcogen are discussed.
New physical evidence to support a ketyl radical-anion mechanism for the [3,3]-sigmatropic rearrangement is presented. With use of EPR spectroscopy, spectra are observed that can be attributed to 8, an acyl radical-anion species resulting from a [3,3]-rearrangement; this also functions as a key intermediate in the process. The spectrum of an additional paramagnetic species resulting from further addition of tin-centered radicals to the reaction product was also observed.
reactions of organo-metal compounds reactions of organo-metal compounds O 0350
-069Radical Reactions of Enones with Electrophilic Allylstannanes.α,β-Unsaturated ketones undergo radical addition reaction with the allylstannane (II) to give the corresponding β-adducts. -(ENHOLM, E. J.; MORAN, K. M.; WHITLEY, P. E.; Tetrahedron Lett. 39 (1998) 9, 971-974; Dep. Chem., Univ. Fla., Gainesville, FL 32611, USA; EN)
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