Imines epoxidation

The use of SSL or lignosulphonates in other polymeric adhesive systems has also been examined [e.g., with polyacrylamide, proteins/aldehydes, polyethylene oxide, polyethylene imine, epoxides, melamine, styrene oxide, polyisocyanates (55)]. So far, these procedures, for different reasons, have not led to any major practical application (36). It would, however, be interesting to reexamine some of these processes using not crude spent sulphite liquors, but instead those purified by membrane filtration. 

Wasserman et al. utilized an intramolecular imine-epoxide ring opening/cyclization process <88TL4973> to synthesize heterotropanes and substituted piperidines (Scheme 20). This methodology has been applied to the total syntheses of piperidine-based alkaloids (+)-teneraic acid <89TL6077> and ( )-solenopsin-A <88TL4977>. 

Mutagen Substance capable of causing a heritable change in the genetic information stored in the DNA. Many chemicals, including imines, epoxides, acrolein, benzene, sulfur, and methylsulfonates, are mutagens. Mutagens can cause fertility... 

Wasserman, H.H., Rodriques, K., and Kucharczyk, R. (1989) The imine-epoxide rearrangement in the formation of trans-2,6-disubstituted piperidines. A stereoselective synthesis of ( )-teneraic... 

Primary and secondary amines also react with epoxides (or in situ produced episulfides )r aziridines)to /J-hydroxyamines (or /J-mercaptoamines or 1,2-diamines). The Michael type iddition of amines to activated C—C double bonds is also a useful synthetic reaction. Rnally unines react readily with. carbonyl compounds to form imines and enamines and with carbo-tylic acid chlorides or esters to give amides which can be reduced to amines with LiAlH (p. Ilf.). All these reactions are often applied in synthesis to produce polycyclic alkaloids with itrogen bridgeheads (J.W. Huffman, 1967) G. Stork, 1963 S.S. Klioze, 1975). 

Lithium aluminum hydride (LiAlH4) is the most powerful of the hydride reagents. It reduces acid chlorides, esters, lactones, acids, anhydrides, aldehydes, ketones and epoxides to alcohols amides, nitriles, imines and oximes to amines primary and secondary alkyl halides and toluenesulfonates to... 

The chapter is divided into three sections, devoted to the discussion of the synthesis of (1) oxiranes (epoxides), (2) aziridines (ethylene imines) and (3) thiiranes (episulfides). 

The Corey-Chaykovsky reaction entails the reaction of a sulfur ylide, either dimethylsulfoxonium methylide (1, Corey s ylide, sometimes known as DMSY) or dimethylsulfonium methylide (2), with electrophile 3 such as carbonyl, olefin, imine, or thiocarbonyl, to offer 4 as the corresponding epoxide, cyclopropane, aziridine, or thiirane. ... 

Fritsch-Bobbitt imine 34 was prepared by reacting amine 33 with chiral epoxide 32. 

The suggested reaction mechanism involves a nucleophilic attack of the imine nitrogen at the activated triple bond, followed by a proton exchange, to give a benzimidazolinium system which, by intramolecular attack at the carbonyl group, leads to an epoxide that ring opens to the observed product. For the ethyl derivative (R = Et) a tub conformation could be established by X-ray crystallographic analysis.33... 

This review summarizes the best asymmetric methods for preparing epoxides and aziridines from aldehydes (or ketones) and imines. 

Asymmetric Synthesis of Epoxides and Aziridines from Aldehydes and Imines... 

Asymmetric transformation of imines into chiral aziridines remains less well developed than the analogous transformation of aldehydes into epoxides [49, 50, 51]. The reported methods can be divided into three conceptual categories involving... 

The aza-Darzens reaction is analogous to the Darzens synthesis of epoxides (see Section 1.2.3.2) but employs imines in the place of aldehydes (Scheme 1.27). 

Of course, the key limitation of the ylide-mediated methods discussed so far is the use of stoichiometric amounts of the chiral reagent. Building on their success with catalytic asymmetric ylide-mediated epoxidation (see Section 1.2.1.2), Aggarwal and co-workers have reported an aza version that provides a highly efficient catalytic asymmetric synthesis of trans-aziridines from imines and diazo compounds or the corresponding tosylhydrazone salts (Scheme 1.43) [68-70]. 

The reactivity of epoxides can be modified by various proximal functionality. For example, 2,3-epoxy sulfides 118 are converted to the corresponding TMS-thiiranium species 119 upon treatment with TMS triflate. This intermediate reacts with O-silyl amides regiospecifically to form l-substituted-3-hydroxy-2-thioethers (e.g., 120). Simple primary amines undergo polyalkylation, but imines can be used as an indirect amine equivalent <96TET3609>. 

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