Acyl iodides RCOI (R = Me, Ph) reacted with morpholine and piperidine to give the corresponding N-acyl derivatives and morpholine or piperidine hydroiodides. Reactions of acyl iodides with N-methyl-and N-ethylpiperidines involved cleavage of the exocyclic R-N bond with formation of N-acylpiperidine and alkyl iodide and were accompanied (to insignificant extent) by cleavage of the endocyclic N-C bond, leading to N-alkyl-N-(5-iodopentyl)acylamides. In the reaction of acetyl iodide with N-phenylpiperidine, the main process was cleavage of just endocyclic N-C bond to produce N-(5-iodopentyl)-N-phenylacetamide and its dehydroiodination product, N-(pent-4-en-1-yl)-N-phenylacetamide. Analogous reaction with benzoyl iodide afforded N-(5-iodopentyl)-N-phenylbenzamide in a poor yield.We previously showed [1] that acyl iodides react with excess primary and secondary amines in a way similar to acyl chlorides (but considerably more readily) to give the corresponding carboxylic acid amides and initial amine hydroiodides. In contrast, reactions of acyl iodides with tertiary amines occur under mild conditions in the absence of a catalyst via cleavage of N-C bond in the amine and formation of the corresponding N,N-disubstituted carboxylic acid amides and alkyl iodides (Scheme 1).Acetyl and benzoyl iodides RCOI (R = Me, Ph) reacted with 2 equiv of morpholine or piperidine in methylene chloride at room temperature to give the corresponding N-acylated amines and amine hydroiodides (Scheme 2); analogous products were formed in the reactions with acyclic secondary amines. It should be noted that, unlike ethers [2], the C-O-C fragment in morpholine molecule remained intact under the given conditions.
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