[reaction: see text] This Mg-TiCl4-promoted CH2-transfer reaction of CH2Cl2 represents an extremely simple, practical, and efficient methylenation of a variety of ketones and aldehydes, especially in enolizable or sterically hindered ketones such as 2,2-dimethylcyclohexanone, camphor, and fenchone.
Lewis acid catalysis of the ene addition of chloral and bromal to olefins; stereochemical and mechanistic studies
作者:Jill P. Benner、G. Bryon Gill、Stephen J. Parrott、Brian Wallace、Michael J. Begley
DOI:10.1039/p19840000315
日期:——
the additions to olefins of moderate reactivity) indicating the participation of Friedel-Crafts type dipolar intermediates. The ene adducts themselves could be formed via dipolar intermediates or in competing ‘concerted’ reactions; the stepwise mechanism must operate in some reactions because of the observation of Wagner-Meerwein rearrangements. Olefin reactivity over the series, measured by the competitive
Reactions of 1,1-disubstituted olefins with oxone and ammonium thiocyanate in methanol gave the corresponding 1-methoxy-2-thiocyano adducts in various yields.
Wittig-type Reaction of Dimetallated Carbodianion Species as Produced by Zinc Reduction of<i>gem</i>-Polyhalogen Compounds in the Presence of Lewis Acids
Treatment of R1COR2 with a suspension prepared from diiodomethane, trimethylaluminum and excess zinc in tetrahydrofuran at room temperature affords olefins R1R2C=CH2 in fair (R1,R2=alkyl) to good (R1=alkyl, R2=H) yields. The ketone methylenation is better carried with another system consisting of CH2Br2–Zn–TiCl4. Ketones and aldehydes are transformed into α-chloro α,β-unsaturated esters or α,β-unsaturated
Rhodium(II) acetate catalyzed intermolecular cyclopropanationreactions of cyclic diazoamides with exocyclic olefins are describedto furnish an assortment of stable strained dispirocyclic cyclopropanesystems in good yields under mild experimental conditions.