Development of catalytic reactions via π-allyl iridium intermediate

点击翻译按钮获取中文摘要

Iridium complexes have been used as a hydrogenation catalyst. Much less attention has been paid to iridium complex-catalyzed carbon-carbon bond formation. We first showed that [Ir(cod)Cl]_2/4P(Oph)_3 is an efficient catalyst for allylic alkylation. The reaction proceeds via π-allyl iridium intermediate, which is formed by oxidative addition of allylic esters to an iridium complex. The chemistry of π-allyl iridium intermediate should be useful for organic synthesis. The aim of this research project is to develop catalytic reactions via π-allyl iridium intermediate.1. Allylic animationWe found that an iridium complex is an efficient catalyst for allylic animation. The solvent strongly affected the catalytic activity. The use of a polar solvent such as EtOH is essential for obtaining the products in high yield. The reaction of (E)-3-substituted-2-propenyl carbonate and 1-substituted-2-propenyl carbonate with pyrrolidine in the presence of a catalytic amount of [Ir(cod)Cl]_2/4P(Oph)_3 gave … More a branched amine with up to 99 % selectivity. Both secondary and primary amines could be used. When a primary amine was used, selective monoallylation occurred. No diallylation product was obtained. The reaction of 1,1-disubstituted-2-propenyl acetate with amines exclusively gave an α,α-disubstituted allylic amine. This reaction provides an alternative route to the addition of an organometallic reagent to ketimines for preparation of such amines. The reaction of (Ζ)-3-substituted-2-propenyl carbonate with amines gave (Ζ)-linear amines with up to 100 % selectivity. In all cases, no (Ε)-linear amine was obtained. The selectivities described here have not been achieved in similar palladium complex-catalyzed reactions.2. Allylic alkylation of enynyl acetatesWe examined allylic alkylation of enynyl acetates. The reaction of 2-ethenyl-2-heptynyl acetate with diethyl sodiomalonate in the presence of a catalytic amount of [Ir(cod)Cl]_2 and P(Oet)_3 (P/Ir = 2) gave a branched product in 92 % selectivity. The reaction proceeds via 1-(1-alkynyl)-π-allyl iridium intermediate. We achieved a highly regioselective alkylation at 1-(1-alkynyl)-substituted allylic terminus. Less