Imine salts from amides

Dai and coworkers have investigated the addition of ylides derived from allylic sulfonium salts to IV-sulfonyl imines derived from aromatic aldehydes to produce 2-vinyl aziridines [98]. The general reaction studied is shown in Eq. (69), where a sulfonium salt 285 can be converted to its ylide in situ under either phase transfer conditions, or by use of a strong amides base, and then combined with an N-sulfonyl imine to provide a 2-vinyl aziridine 286. In gene-... 

The cycloaddition of keteniminium triflates 195, formed from tertiary amides by the action of triflic anhydride, with imines formed the azetidine iminium salts 196 (Equation 51) <1996JOC8480>. 

As described above, the reduction of imines often proceeds via iminium ions particularly in acidic media, since protonation enhances the electrophilicity of the imine carbon. Thus, as expected, preformed iminium salts generated from carbonyls and secondary amines are also readily reduced by most hydride reagents. Several examples of synthetic applications with a variety of reagents are illustrated in Table 4. Entries 9-12 illustrate the use of iminium intermediates for the reductive removal of amide carbonyls. Thus, treatment of amides with POCI3 affords the iminium derivatives (e.g. 9 Scheme 3), which are reduced by NaBHt to the corresponding amines (Table 4, entries 9, 10). Likewise, reaction of amides witii trialkyloxonium salts to give imidic esters (entry 12) or thioamides with methyl iodide to give... 

Low-valent metal salts have been used to bring about reductive cleavage of oximes. Corey and Rich-man used chromium(II) acetate to convert O-acetyl ketoximes into imines, which were hydrolyzed to ketones. " Aqueous titanium(III) chloride and vanadium(II) salts also reduce oximes again, the imines are usually hydrolyzed in situ, but some hindered imines, such as compound (37), are isolable." A method of preventing hydrolysis is to carry out the reduction in anhydrous conditions in the presence of an acylating agent. The products of such reactions, when applied to oximes of enolizable ketones, are en-amides. For example, these ketoximes are converted into A/-formylenamines when heated in acetonitrile with anhydrous titanium(III) acetate and acetic formic anhydride cyclohexanone oxime gives the en-amide (38 97% Scheme 22)." This type of reduction has been used by Barton and coworkers to prepare enamides from steroidal oximes. They reported that the reaction could be performed by acetic... 

Amino-l,2-dithiolium salts are obtained from either / -oxocarbox-amides or ) -oxocarbonitriles by reaction with phosphorus penta-sulfide, followed by addition of perchloric acid (Scheme 6). These cations, which may also be considered as iminium salts, are deprotonated to the corresponding l,2-dithiol-3-imine by ammonia. ... 

Discussed in this chapter, for the most part, are documented cases where complexes derived from (one or more equivalents of) a Grignard or organolithium reagent, in combination with a copperfl) salt, have been used to add to an aldehyde, ketone, imine, amide or nitrile moiety. In the majority of examples, the key issue is one of stereocontrol. Hence, where available, data within the organocopper manifold versus those for other organometallic reagents are provided for comparison. 

Sonn-Miiller method The reduction of an aromatic amide to an aldehyde, in which the intermediate HC1 salt of the imine is formed from the amide and PC15. This salt is then reduced to... 

Phosphoranylideneaminoquinones, e.g. (20), have been prepared in good to excellent yields by the reaction of phosphines with [2,l]benzisoxazole-4,7-quinones, e.g. (19)." A safer alternative to the vinyl azide-based synthesis of (N-vinylimino)phosphoranes (21) has been reported (Scheme 1)." N-(AlkyIthiomethyl)iminophosphoranes (23) have been synthesised from the benzotriazole-substituted iminophosphorane (22) and used without isolation to provide routes to N-alkylthiomethyl-imines, -amides, and -ureas. Tetraazolyl-substituted ylides (25) and (26) are the products of the reaction of vinylphosphonium salts (24) with excess sodium azide." The novel 1,2-1 -azaphosphete (28), which is potentially antiaromatic, has been prepared by the reaction of the azide... 

Sulphonedi-imines are sufficiently nucleophilic to displace halogen from reactive halides. Thus, reaction with CICN in the presence of triethylamine afforded the mono- or bis-cyano-derivative depending on the molar ratio of reactants used. The bis-cyano-derivative (119) was not sufficiently nucleophilic to form salts in the presence of acid. Acid hydrolysis afforded the bis-amide, and treatment with acetyl chloride in aqueous acetonitrile... 

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