Treatment of various organic halides with phosphinic acid (hypophosphorous acid) in aqueous ethanol in the presence of a radical initiator and a base gave the corresponding reduced products in high yields. Addition of a base is indispensable for the reduction of halides by phosphinic acid. Allylic ether of o-iodophenol or 2-haloalkanal allylic acetal underwent radical cyclization under the same conditions
Tri-2-furylgermane proved to be an effective reagent for the radical reduction of organichalides. Treatment of 1-bromododecane with tri-2-furylgermane in THF at 25 °C in the presence of a catalytic amount of triethylborane afforded dodecane almost quantitatively. Radical cyclization of 2-iodoethanal allyl acetal afforded five-membered products under the same reaction conditions. These reactions proceeded
Catalytic amounts of cobalt complexes 2 and 3 are capable of generating alkyl radicals from the corresponding bromides under mild readion conditions, allowing the selective preparation of either saturated or unsaturatedradicalcyclization products.
Treatment of allylic ether of 2-iodophenol or 2-haloethanal allylic acetal with phosphinic acid, a base and a radical initiator (AIBN or triethylborane) in aqueous ethanol provided the corresponding radical cyclization product in excellent yield. An addition of a base is critical to employ phosphinic acid as a radical mediator.
Intramolecular Radical Cyclization of 2-Haloethanal Allyl Acetal and Allyl 2-Halophenyl Ether with a Grignard Reagent in the Presence of Iron(II) Chloride