Preparation of 3-aza-Cope rearrangement of N-alkyl-N-allyl enamines
摘要:
The [3,3] charge-accelerated rearrangement of N-allyl-N-isobutyl enamine substrates to gamma,delta-unsaturated imine products and subsequent reduction to the corresponding N-alkyl delta,epsilon-unsaturated amines is reported. Several routes to the N-allyl-N-isobutyl enamines were established for the enamine prepared from isobutyraldehyde. With use of the most efficient route developed, enamines derived from butanal, 2-phenylpropanal, cyclohexanone, and cyclopentanone were prepared in 58 to 92% overall yield in three steps from allylamine. In the case of butanal, the E isomer was formed exclusively, while the enamine from 2-phenylpropanal was prepared with an E to Z selectivity of 86:14. Heating these N-allyl-N-isobutyl enamines in refluxing dioxane with 0.5 equiv of HCl produced [3,3] rearrangement for substrates derived from isobutyraldehyde, 2-phenylpropanal, and cyclohexanone; the enamines of n-butanal and cyclopentanone were found to react through alternate pathways.
An Effective Method To Prepare Imines from Aldehyde, Bromide/Epoxide, and Aqueous Ammonia
作者:Jing-Mei Huang、Jue-Fei Zhang、Yi Dong、Wen Gong
DOI:10.1021/jo102455q
日期:2011.5.6
three-component reaction of aldehydes, alkyl bromides, and ammonia to form imines was studied. Aqueous ammonia was applied as the nitrogen source and solvent in the reaction. For the aromatic aldehyde, the product yields are good to excellent and the reaction conditions are mild to be compatible with a range of functional groups. The reaction of aldehydes and aqueous ammonia with epoxides was also studied and