We have demonstrated for the first time that carboxylic ortho esters could be used as an alkylating agent in the reductive alkylation of amines. A variety of amines, including amino acid esters, were alkylated affording mono‐alkylated products with high selectivity in practical to high yields using standard heterogeneous catalysts. By applying acyclic ortho esters alkylation was completed at room temperature.magnified image
The allylthio nitrones (IV) and (VIII), derived from mercaptoacetaldehyde (I) and allyl bromide (II) or from acrolein (VI) and allyl mercaptan (VII), undergo intramolecular cycloaddition, forming the fused isoxazolidines (V) or (X) and the bridged oxathiazine derivatives (IX).
087ChemInform Abstract The nitrones (III) are converted to the cyclized products (IV), whereas similar nitrones formed from aldehydes such as (V) under similar conditions are immediately cyclized, e.g. to (VI). In contrast, out of similarly formed nitrones such as (VII), only N-alkyl compounds, e.g. (VIIa), (VIIb) can be isolated affording subsequently products such as (VIII) and (IX) on heating, whereas N-aryl compounds, e.g. (VIIc), (VIId), are spontaneously dimerized (→ e.g. (X)). However, dimerization is reversible, and subsequent heating ikewise affords the product types (XI) and (XII). -In addition, some hydrogenation reactions of (XIa), (XIb) and (XIIb) are studied.
Oxidation of hydroxylamines (I) with excess PbO2 within an ESR tube at first affords nitroxides (II) which on further oxidation generate the vinyl nitroxides (IV) via nitrone intermediates (III).
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