Cyclizations of ω-Alkynyl Halides by Cr(II) Reduction
Reduction of halides of the types RCC(CH2)nX with Cr(II) in aqueous DMF containing ethylenediamine proceeds by way of the intermediate radicals which cyclize regioselectively in the n=4 and n=5 cases to give substituted methylenecycloalkanes.Experimental conditions which favor longer lifetimes for the intermediate radicals (low concentrations, slow addition times, and an inverse-addition mode) result in increased cyclization.The iodides curiously give more cyclic product than the corresponding bromides.These results are discussed.
Crandall, Jack. K.,Michaely, W. J.
p. 4244 - 4248
(2007/10/02)
-CYCLOADDITIONS OF CYCLOPENTYNE
Cyclopentyne, as generated from dibromomethylenecyclobutane, a formerly unknown cyclopentyne source, undergoes -cycloadditions with various substituted olefins yielding bicyclohept-1(5)-ene derivatives.
Fitjer, Lutz,Kliebisch, Ursula,Wehle, Detlef,Modaressi, Said
p. 1661 - 1664
(2007/10/02)
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