Cyclic stereocontrol via organobismetallic reagents. Part V. Diastereoselective synthesis of substituted cyclopropyl zinc reagents by the metalla-claisen reaction

Carbozincation Reactions of Carbon–Carbon Multiple Bonds

“…Alkenes metalated at the internal carbon of the double bond may also be employed as illustrated in Scheme 130 156 and Scheme 131. 157 Of special interest in the latter reaction is the addition of a functionalized allylic zinc reagent such as [2-(methoxymethoxy)-2-propenyl]zinc bromide, since it allows a formal site-selective addition of an acetonyl moiety across the styrene double bond (Scheme 131).…”

Recent Advances in Synthesis of Cyclopropanes

“…Treatment of functionalized vinyllithium, 28, with allylmagnesium bromide in the presence of zinc bromide leads to a stereoselectively substituted, metallated cyclopropane, 29, via a tandem metalla-Claisen-cyclization reaction (equation 48) 64 . The produced cyclopropylzinc reagent serves as a unique nucleophilic reagent bearing a quaternary chiral (48) carbon, as exemplified by the conversion into the corresponding bromo-and iodocyclopropanes with bromine and iodine, respectively, and into a copper reagent, via metal-metal exchange, from which a variety of stereoselectively 1,1,2-trialkylated cyclopropanes are prepared.…”

“…Exploiting the chemoselectivity of this reagent, 2-alkylidenecyclopropanemethanols are prepared from α-allenic alcohols (equation 64) 98 . In addition to allylic alcohols, the (64) diiodomethane/samarium system is capable of cyclopropanating lithium enolates to produce cyclopropanols in a one-pot synthesis from ketones (equation 65) 99,100 . α-Halogenated ketones are directly and regioselectively converted into cyclopropanols via samarium enolates (equation 66) 100 .…”

Synthesis and Reactivity of sp3-Geminated Organodimetallics

“…147 The syn stereochemistry between the butenyl and butyl residues is explained by the W-shaped transition state. Then, in this case, the 1,3 steric interaction has no effect on the stereochemical outcome of this cyclization.…”

“…The tertiary cyclopropyl zinc halide can be also transmetalated to copper and then reacted with ethyl propiolate, allyl iodide, or an amino ether to give the corresponding functionalized cyclopropanes as a single diastereomer (one-pot creation of three carbon−carbon bonds) . The syn stereochemistry between the butenyl and butyl residues is explained by the W-shaped transition state.…”