Reactions of the Lithium Salts of the Tribenzylidenemethane Dianion, Diphenylacetone Dianion, and Related Compounds
摘要:
Potentially synthetically useful reactions of the dilithium salts of the title dianions have been investigated, Electrophilic quenching with a variety of reagents usually leads to the expected products in good yield. Quenching the diphenylacetone dianion with 1 equiv of trimethylchlorosilane, however, gives a good yield of 1,3-diphenylallene obtained by formal elimination of a trimethylsiloxy anion from an intermediate monoquenched monoanion salt. NMR studies, however, do not reveal the intermediacy of the 1,3-diphenyl-2-(trimethylsiloxy)allyl anion but rather suggest that the initial reaction site is at carbon, rather than oxygen, Oxidation of the dianions leads either to ring closure or dimerization for the tribenzylidenemethane dianion and to dimerization for the diphenylacetone dianion. The dimerization reactions are stereospecific, both with respect to the two new stereocenters produced and for the double bonds of the bis-silyl enol ether products if the dimeric bis-enolate dianion products are quenched with trimethylchlorosilane.
We report here a C–H homoallylation reaction of aromaticketones with methylenecyclopropanes (MCPs) only using a catalytic amount of Fe(PMe3)4. A variety of aromaticketones and MCPs are applicable to the reaction to form ortho-homoallylated aromaticketones selectively via regioselective scission of the three-membered rings. The homoallylated products are amenable to further elaborations, providing
Unwringing the ring: Methylenecyclopropanes reacted with vinyl and aryl Grignard reagents in the presence of a nickel catalyst to afford vinyl‐ and arylmagnesation products, respectively, through a selective CC bondcleavage (see scheme). The reaction provides a new method for the preparation of substituted homoallyl and allyl Grignard reagents.
A Cu-catalyzed aminoboration of 1-methylenecyclopropanes with bis(pinacolato)diboron and O-benzoyl-N,N-dialkylhydroxylamines has been developed. The Cu catalysis provides a rapid and concise access to (borylmethyl)cyclopropylamines in a highly regio- and diastereoselective manner. The products obtained can be useful building blocks for the synthesis of potential antidepressants, trans-2-arylcyclopropylamine
A copper-catalyzed ring-opening hydroamination of methylenecyclopropanes with polymethylhydrosiloxane and O-benzoylhydroxylamines has been developed. The cyclopropane C–C bond cleavage occurs selectively at the more congested proximal position, and the corresponding homoallylamines are obtained in good to excellent yields. The umpolung electrophilic amination strategy with the hydroxylamine derivatives