N-alkyl bonds

We will demonstrate the synthesis of n-alkyl bonded silicas by chemical surface modification and their properties. 

Mass Spectrometry.—Mass spectral data have been tabulated for a number of aziridines, including cis- and rra j-2-aroylaziridines in which a simple fission of the N—alkyl bond appears to take place. 

Sulfonium ylides may be added to C N double bonds to yield aziridines in a formal [1 -t-2]-cycloaddition. Alkyl azides are decomposed upon heating or irradiating to yield ni-trenes, which may also undergo [ 1 + 2 -cycloaddition reactions to yield highly strained hetero-cycles (A.G. Hortmann, 1972). 

Oxidative Ring Closure Reactions 4.03.4.1.1 C—N bond formation N—N bond formation C—S bond formation N—S bond formation O—C bond formation O—N bond formation S—S, S—Se and Se—Se bond formation Electrophilic Ring Closures via Acylium Ions and Related Intermediates Ring Closures via Intramolecular Alkylations... 

Among unsaturated C—N—N three-membered rings only the 3H-diazirines (3) are known. IH-Diazirines with a C=N double bond were never obtained. Diazirines with one or two alkyl groups at carbon were prepared in many cases, aryldiazirines only in some cases. An important role is played by difluorodiazirine as well as by diazirines containing chlorine or bromine (9). 

The general rule has been formulated (P) that the less substituted enamine is formed from unsymmetrical ketones such as the 2-alkylcyclohexanones. In enamine 21 the R, group and the N-alkyl groups would interfere with one another if overlap is to be maintained between the nitrogen unshared electrons and the double bond. There would be less repulsion if the isomeric enamine (22) were formed. 2-Phenylcyclohexanone and pyrrolidine with p-toluenesulfonic acid as catalyst in refluxing benzene gave enamine... 

The course of alkylation is also influenced by the steric arrangement of the enamine. 1-Pyrrolidino-l-cycloheptene gave approximately equal quantities of the C- and N-alkylated products in dioxane, while 1-pyrroli-dino-l-cyclooctene, and 1-pyrrolidino-l-cyclononene afforded N-alkylated products exclusively under similar eonditions (29). The reason for N alkylation in the eight- and nine-membered ring compounds is to be found in the conformation of these rings, which prevents full interaction of the unshared electrons on nitrogen with the n eleetrons of the double bond. 

The alkaloids cotamine (259), hydrastinine (261), and berberinal (260), each possessing a grouping formed by interaction of an aldehyde with a secondary amino group in their molecule, are unusual. The Grignard reaction of free base 166 does not occur as readily as that of the corresponding salt 167. Both reactions lead to the alkylated product 168. For example, only 50% of hydrastinine reacts and 50% is regenerated, whereas hydrastinine hydrochloride reacts almost quantitatively (261). The salt undoubtedly contains a C=N double bond. In the case of the free base, the presence of a C=N double bond was not proven, and the reaction probably occurs by direct cleavage of the C—OH bond. 

Carbamates are formed from an amine with a wide variety of reagents, the chlo-roformate being the most common amides are formed from the acid chloride. n-Alkyl carbamates are cleaved by acid-catalyzed hydrolysis A-alkylamides are cleaved by acidic or basic hydrolysis at reflux and by ammonolysis, conditions that cleave peptide bonds. 

There has as yet been no systematic work on the mass spectra of cyclic hydroxamic acids, but from the limited information available the direct loss of 0 or OH from the molecular ion is to be expected. The fragmentation behavior of the 0-alkyl derivatives is rather unpredictable, although again processes involving fission of the N—0 bond are generally important. Table II shows the prominent first-generation fragment ions from a few hydroxamic acids and their ethers. 

Following the radical pathway" the next step is a homolytical cleavage of the N-R bond. The rearrangement to yield the tertiary amine 3 then proceeds via an intermediate radical-pair 4a. The order of migration is propargyl > allyl > benzyl > alkyl ... 

A series of bonded poly(alkyl aspartamide) coatings was prepared on silica by analogy to the method described above. Poly(succinimide) coating was reacted with n-alkyl- and arylalkylamines in dimethylformamide to yield a series of hydrophobic adsorbents. Poly(propyl aspartamide)-silica (PolyPROPYL A) showed the maximal reversible hydrophobic binding of hemoglobin among the Cl -C5... 

Kim and coworkers introduced silyl radical mediated addition of alkyl radical to silyloxy enamine 76. The silyloxy enamine moiety is readily accessible from a variety of functionalities. The mechanistic concept is illustrated in the Scheme 12 and involves the addition of R radical to 76 to give the radical adduct 77 and the subsequent homolytic cleavage of N-O bond to yield the desired product 78 and a silyloxy radical 79. The latter undergoes 1,2-phenyl migration to give the silyl radical 80 that abstracts halogen from the alkyl halide to regenerate the R radical. 

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