Imines, amines from rearrangement

The heteroatom version of the vinylcyclopropane rearrangement serves to facilitate alkaloid construction. Scheme 13 outlines a strategy for the pyrrolizidine alkaloid isoretronecanol 211 90). Use of a carboxaldehyde (i.e. 213) as a synthon for the primary alcohol provides an ability to adjust stereochemistry. It also sets up formation of the pyrrolidine ring bearing the aldehyde by an aldol-type condensation of an enol of the aldehyde onto an imine derived from 214. Because of the lability of such systems, introduction of X=PhS imparts stability. The resultant azacyclopentene translates to an imine 215 using the iminocyclopropane rearrangement methodology. Simple condensation of the primary amine 216 with aldehyde 37a then initiates this... 

Imines derived from ketones with an a-methylene group can react via their enamine tautomers, and mixtures of triazoles are also isolated from these systems. The triazoline adducts of the enamine tautomers are aromatized by treating with acid, and in these conditions the triazoline appears to undergo a Dimroth rearrangement before elimination of the amine, because two triazoles are obtained, one of which has... 

Other types of allylic amination reactions include a variety of indirect approaches such as reduction of a,P-unsaturated imines and oximes, rearrangement of aziridines, and elimination of water from vicinal amino alcohols. However, these reactions will not be considered in this chapter [2]. 

Prim, and sec. amines from oximes Reductive rearrangement s. 72, 411 Cyclic imines from alicyclic nitro compounds... 

Later on, Ren and Wulff [53] reported that a combination of the chiral catalyst VANOL-B3 29, derived from the reaction of binaphthol derivative VANOL with triphenyl-borate, also afforded good results in the asymmetric catalytic aminoallylation of a series of aromatic, aliphatic, and a,P-unsaturated aldehydes. Catalytic amounts of benzoic acid were required to ensure the formation of the intermediate imines, and the rearranged imines were hydrolyzed in situ to afford the homoaUylic amines (Scheme 40.44). 

Aliphatic c a -dibromo ketones, such as 2,4-dibromopentan-3-one (262), react with primary amines RNH2 (R = Me, Et, Pr, /-Pr or t-Bu) to give mixtures of imines 263 and lesser amounts of diimines 264. l,3-Dibromo-l-phenylpropan-2-one yields only the amide 265, the product of a Favorskii rearrangement. The nature of the products from aliphatic amines and cyclic a,a -dibromo ketones depends on ring size the cyclohexanone derivative 266 gave Favorskii amides 267 (R = Pr, /-Pr or t-Bu), while trans-2,5-dibromocyclopentanone afforded the enamines 268 (R = /-Pr or t-Bu) (equation 95)296. 

A related amination/rearrangement/cyclization tandem sequence had been introduced by Cossy [49]. Starting from cyclic epoxyketones 224 the reaction with propargylamines 225 caused an oxirane-opening condensation process to generate the enaminoketones 226. Upon heating in toluene to reflux, aza-Claisen rearrangement delivered the intermediate allenyl imines 227, which... 

Reed and Lwowski (38) have done the photolysis of 1-azidonor-bornane (84) in MeOH and obtained two amines (85 and 86) in 54 and 24% yields, respectively. In the course of intramolecular nitrene rearrangements, an anti-Bredt s rule imine, 2-azabicyclo[3.2.1]oct-l-ene (87), can be regarded as a plausible intermediate from which the amine 85 is produced. On the other hand, a biradical 88 has been... 

The effect of substituents on C(2) of vinyl bromide and on the amine of the palladium catalyst in the. S n reaction with secondary amines was examined. The catalyst formed from the reaction of Pd2(dba)3 with proazaphosphatrane (12) gave the best yields (>91%) of enamine.16 The. S n product formed with primary amines rearranged to give the imine as the product in yields of >86%. 

N-Heterocyclics. The reaction of primary amines with the carbonyl products derived from lipid oxidation is a major pathway in lipid-protein interactions. Formation of Schiff s base intermediates followed by cyclization and rearrangement can yield imines, pyridines and pyrroles (5,15,30,31). For example, 2-pentylpyridine may result from the reaction of ammonia with 2,4-decadienal, one of the principle aldehydes from the autoxidation of linoleate (5). 

The —N=C— bond in imines, especially Schiff bases formed from aromatic aldehydes and amines, can be epoxidized by peracids to form oxaziridines [N(0)C].326 Unlike epoxides, oxaziridines will oxygen-transfer.327 Chiral oxaziridines have been used to carry out enantioselective epoxidations,328 although these compounds are often prepared by non-peroxygen routes.329 Oxaziridines can also be rearranged to oximes or nitrones (Figure 3.85).330... 

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