Dimethylation and Hydrodechlorination ofgem-Dichlorocyclopropanes with Grignard Reagents Promoted by Fe(III) or Co(II) Catalyst

Abstract

Reactions of gem-dichlorocyclopropanes with MeMgBr or t-BuMgCl were examined in the presence of Fe, Co, and Ni (group VIIIA, first transition series) catalysts. The Fe(dbm) 3 catalyst promoted dimethylations of gem-dichlorocyclopropanes in the presence of 4methoxytoluene or p-xylene. In contrast, CoCl 2 (dppe) conducted their hydrodechlorination.Transformations of gem-dihalocyclopropanes into functionalized cyclopropanes are useful synthetic methods, 1 due to the preparative accessibility of gem-dihalocyclopropanes. A number of reductive hydrodehalogenations were extensively studied as a basic functionalization. 2 Several efficient methods have been exploited for the double carbon-elongations mediated by the ate transient complexes of Cu, 3 B, 4 Zn, 5 and Mn. 6 Giese-type sequential stereocontrolled couplings using Bu 3 SnH were also reported. 7

Hydrodehalogenation of 1,1-dibromocyclopropanes by Grignard reagents promoted by titanium compounds †

“…Since the publication of the preliminary results of the present work it has also been reported that Grignard reagents do reduce 1,1-dichlorocyclopropanes in the presence of either cobalt() chloride or Fe(dbm) 3 . 47 In order to try to determine the mechanism of the reaction in the presence of titanium isopropoxide, and to explain the apparent differences between methylmagnesium bromide and ethylmagnesium bromide, a series of control experiments has been carried out. It was first necessary to determine whether a range of alkylmagnesium bromides would react with a dibromocyclopropane in the absence of the titanium-based catalyst.…”

Transition Metal‐Catalyzed Carbon−Carbon Bond Formation with Grignard Reagents − Novel Reactions with a Classic Reagent

“…The reaction of gem-dichlorocyclopropanes with methylmagnesium bromide in the presence of an iron catalyst provided dimethylated cyclopropanes, although the reaction mechanism was not elucidated (Scheme 33). [41] Scheme 33 Highly regioselective coupling of allyl phosphates with Grignard reagents can be accomplished under iron catalysis (Scheme 34). [42] In the presence of a catalytic amount of Fe(acac) 3 , the reaction provides S N 2 substitution products with high selectivity over S N 2Ј products.…”

Regio‐ and Stereoselective Approach to 1,2‐Di‐ and 1,1,2‐Trisilylethenes by Cobalt‐Mediated Reaction of Silyl‐Substituted Dibromomethanes with Silylmethylmagnesium Reagents

“…This observation encouraged us to explore the potential of silylated dibromomethanes7 as precursors for multiply silylated ethenes (Scheme , bottom). Herein we report an inherently regioselective and, fortunately, stereoselective preparation of 1,2‐di‐ and 1,1,2‐trisilylethenes by means of a cobalt salt, thus creating a novel approach toward multiply silylated ethenes 8. 9 …”