Homolytic carbocyclization by use of a heterogeneous supported organotin catalyst. A new synthetic route to 2-alkoxytetrahydrofurans and .gamma.-butyrolactones
gallium hydride reagent, HGaCl2, was found to act as a radical mediator, like tributyltin hydride. Treatment of alkyl halides with the gallium hydride reagent, generated from gallium trichloride and sodium bis(2-methoxyethoxy)aluminum hydride, provided the corresponding reduced products in excellent yields. Radicalcyclization of halo acetals was also successful with not only the stoichiometric gallium
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
A new strategy for the preparation of an active Mn(0) and its use for radical cyclization reactions
作者:Jun Tang、Hiroshi Shinokubo、Koichiro Oshima
DOI:10.1016/s0040-4020(98)01205-8
日期:1999.2
Reduction of Li2MnCl4 with magnesium in THF afforded a fairly active manganese species which readily initiated radical cyclization of 2-iodoethanal allylic acetals at room temperature. The corresponding 2-bromoethanal acetals also provided the same cyclized products upon treatment with the activated manganese reagent at reflux in THF. This reagent can also be used to induce tandem radical cyclizations
A gallium hydride reagent, HGaCl2, was found to act as a radical mediator. Treatment of alkyl halides with the gallium hydride reagent, generated from gallium trichloride and sodium bis(2-methoxyethoxy)aluminum hydride, provided the corresponding reduced products in excellent yields. Radicalcyclization of halo acetals was also successful with not only the stoichiometric gallium reagent but also a
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.