Facile 5-endo electrophilic cyclization of unsaturated amides with tBuOCl/I2
摘要:
5-Endo iodocyclization of various beta,gamma-unsaturated amides proceeded smoothly to give the corresponding conjugated imino-lactones exclusively in satisfactory yields with the use of (BuOCl)-Bu-1 and I-2 as the reagents, which proved to be much advantageous over the conventional I-2/NaHCO3. (c) 2006 Elsevier Ltd. All rights reserved.
The reaction of 4-alkyl-4-hydroxy-2-alkynenitrites with hydrogen halides (HCl and HI) in dioxane is accompanied by intramolecular cyclization with formation of 5,5-dialkyl-4-halo-2-imino-2,5-dihydrofuran hydrohalides. Treatment of the latter with K2CO3 in ethanol yields 5,5-dialkyl-4-halo-2-imino-2,5-diliydrofurans.