Arylidene imines

Compounds of the general formula 69 are prepared by cycloaddition of N-methyl- or A(-arylmaleimides with arylidene imines of AAs and in the presence of an aromatic aldehyde. Stabilized azomethine ylides are formed as intermediates, which then afford the cycloadducts. Several isomers are formed, and the influence of various metal salts and solvents was investigated (87BCJ4067 88T557). Similar transformations have been performed with A-ailyl glycine esters (91TL1359). 

Grigg and co-workers (383) found that chiral cobalt and manganese complexes are capable of inducing enantioselectivity in 1,3-dipolar cycloadditions of azomethine ylides derived from arylidene imines of glycine (Scheme 12.91). This work was published in 1991 and is the first example of a metal-catalyzed asymmetric 1,3-dipolar cycloaddition. The reaction of the azomethine yhde 284a with methyl acrylate 285 required a stoichiometric amount of cobalt and 2 equiv of the chiral ephedrine ligand. Up to 96% ee was obtained for the 1,3-dipolar cycloaddition product 286a. 

Decarboxylative condensations of this type are sometimes carried out in pyridine, which cannot form an imine intermediate, but has been shown to catalyze the decarboxylation of arylidene malonic acids.215 The decarboxylation occurs by concerted decomposition of the adduct of pyridine to the a, 3-unsaturated diacid. 

A method that makes available aromatic and aliphatic aldehyde derived sulfin-imines 47, for the first time, was recently introduced by Davis and co-workers.23,36 This one-pot procedure entails treatment of the Andersen reagent 40 with LiHMDS to generate 44 which subsequently reacts with the lithium methoxide by-product to produce silyl sulfinamide anion 46. Reaction of 46 with the aldehyde in a Peterson-type olefination reaction affords the sulfinimine 47 in >96% ee. This method was highly effective for the preparation of arylidene sulfmamides 47 (R = aryl) which were usually obtained in 60-76% yield although the alkyl counterparts... 

Durch Michael-Addition von 5-Amino-lH-pyrazolen an 2-Aryliden-3-oxo-butansaure-cstcrn und Cyclokondensation sind 5-Alkoxycarbonyl-4-aryl-4,7-dihydro-lH- (75-85%) zuganglich als Nebenprodukt bilden sich durch Aryliden-Ubertragung die Imine der 5-Amino-lH-pyrazole, die chromatographisch abgetrennt wer-... 

There has been interest in the functionalization of thioindoxyl in the 2-position. 2-Arylidene derivatives are readily formed by reaction with ArCHO2,85 treatment of thioindoxyl with CS2-NaOH, followed by methylation, gives mainly the 2-CS SMe derivative277 reductive acetylation of the 2-nitroso derivative gives 2-acetamidothioindoxyl278 and reaction of thioindoxyl with HCN-HC1 gives the 2-carboxaldehyde, via the imine.279... 

This fragmentation mode was minor or absent under the following conditions (a) in the absence of an ortho-nitro group on the S-aryl ring, as in compounds 169b, k, 1 (b) when the AT-arylidene group was replaced by a iV-alkylidene, as in compounds 170 and 171 (c) when the imine functional group was saturated, as in compound 172. 

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