Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Diiodomethane, carbenoid generation from

Reactions of halogen-stabilized carbenoids with imines have been carried out using preformed lithium species e.g. equation or via a carbenoid generated from diiodomethane utilizing zinc-copper... [Pg.835]

Reactions of halogen-stabilized carbenoids with imines have been carried out using prefoimed lithium species (e.g. equation 36), or via a carbenoid generated from diiodomethane utilizing zinc-copper couple (Simmons-Smith conditions). A stereospecific ring closure is observed after the addition of lithiodichloromethane to a benzaldimine (equation 37).The addition of lithiochloro(phenylsulfon-yl)methane to aromatic imines affords 2-phenylsulfonyl-substituted aziridines, which can be deproton-ated and alkylated in excellent yield (Scheme 20). [Pg.835]

The carbenoid generated from diiodomethane/diethylzinc is often found to be more reactive than the conventional Simmons-Smith reagent. Thus, in the case of 1-alkenylboronic acid esters, where diazomethane failed to cyclopropanate trisubstituted derivatives (Section 1.2.1.1.1.) diiodomethane/diethylzinc gave good yields of the required products 16. ... [Pg.268]

A cyclopropanation of an alkene using the carbenoid reagent generated from diiodomethane and the zinc-copper couple, (p. 358)... [Pg.386]

Another reaction that builds a cyclopropane ring onto a carbon-carbon double bond is called the Simmons-Smith reaction. This reaction does not actually involve a car-bene, but rather a carbenoid, an organometallic species that reacts like a carbene. This species is generated by reaction of diiodomethane with zinc metal from a special alloy of zinc and copper ... [Pg.437]

Simmons—Smith Cyclopropanation. Simmons-Smith cyclopropana-tions have been known for many years as an efficient method for cyclopropanation via methylene transfer to olefinic substrates. Although a stoichiometric amount of reagent is mostly required, the superior reactivity and selectivity make the method inseparable from cyclopropanation. The classical Simmons-Smith cyclopropanation involves a zinc carbenoid reagent (IZnCH2l) generated by the oxidative addition of metallic zinc to diiodomethane by a copper metal as an activator (48). This somewhat cumbersome procedure was later replaced by other more easily accessible and reproducible methods. The benchmark replaces the... [Pg.880]


See other pages where Diiodomethane, carbenoid generation from is mentioned: [Pg.72]    [Pg.429]    [Pg.470]    [Pg.846]    [Pg.25]   
See also in sourсe #XX -- [ Pg.1108 ]

See also in sourсe #XX -- [ Pg.1108 ]




SEARCH



Carbenoid

Carbenoids

Diiodomethane

Generation from

© 2024 chempedia.info