Acyclic stereoselection in the reaction of nucleophilic reagents with chiral N-acyliminium ions generated from N- |
| |
Authors: | Giardina Mecozzi Petrini |
| |
Institution: | Dipartimento di Scienze Chimiche, Universita di Camerino, via S. Agostino, 1, I-62032 Camerino,Italy. |
| |
Abstract: | Optically active N-1-(phenylsulfonyl)alkyl]imidazolidin-2-ones react at low temperature in the presence of tin tetrachloride to give acyclic N-acyliminium ions. These electrophilic substrates give addition products upon reaction with pi-nucleophiles. Allyltrimethylsilane affords the corresponding allylated products in good yields and high diastereoselectivity. The stereochemical outcome of this process can be rationalized by taking into account the preference of the intermediate N-acyliminium ion for an E configuration that favors the attack of the nucleophile from the si-si face. Disappointing results are obtained using silyl ketene acetals; conversely trimethylsilyl enol ether of acetophenone gives the corresponding adducts in high diastereoselectivity. The utilization of trimethylsilyl enol ether of 2-acetylfuran is particularly interesting since the corresponding adducts are obtained with good diastereoselectivity and the furan ring could be amenable of further synthetic transformations. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|