N-Indolyltriethylborate: A Useful Reagent for Synthesis of C3-Quaternary Indolenines
摘要:
N-Indolyltriethylborate was found to be a useful reagent for dearomatizing C3-alkylation of 3-substituted indoles with both activated and nonactivated alkyl halides to give C3-quaternary indolenines, pyrroloindolines, furoindoline, and hexahydropyridoindoline under mild reaction conditions. The utility of these reagents was demonstrated in the syntheses of a pyrroloindoline-4-cholestene hybrid and debromoflustramine B.
Pyrrole and indoles react smoothly with alkyl halides such as allyl bromide, prenyl bromide, crotyl bromide and propargyl bromide in the presence of zinc metal in THF to afford the corresponding 3- and 2-alkyl pyrrole and 3-alkyl indole derivatives in good yields with high regioselectivity.
Palladium-Catalyzed Enantioselective C-3 Allylation of 3-Substituted-1<i>H</i>-Indoles Using Trialkylboranes
作者:Barry M. Trost、Jean Quancard
DOI:10.1021/ja0608139
日期:2006.5.1
We have developed a new enantioselective C-3 allylation of 3-substituted indoles using allyl alcohol and trialkylboranes. Asymmetric syntheses of 3,3-disubstituted indolines and indolenines in enantiomeric excesses up to 90% have been achieved using the bulky borane 9-BBN-C6H13 as the promoter of the reaction. The dependence of the selectivity on the nature of the borane suggests that the boron reagent has a role beyond promoting ionization of the allyl alcohol. A protocol for oxidation of indolenines to oxindoles has also been developed and led to a formal synthesis of (-)-phenserine.