Palladium on Poly(ethylenimine)

Pd/PEI

[7440-05-3]  · Pd  · Palladium on Poly(ethylenimine)  · (MW 106.42)

(catalyst used for the reduction of alkynes to cis- or trans-alkenes;1 hydrogenolysis of benzyloxycarbonyl protecting groups on peptides2)

Solubility: sol many organic solvents except when deposited on a support such as silica gel; insol water and alcohols.

Form Supplied in: commercially available as deposit on a porous silica support.

Analysis of Reagent Purity: atomic absorption.

Handling, Storage, and Precautions: nonpyrophoric and air stable.

Preparation and Properties.

The deposition of Pd on a minimally cross-linked poly(ethyleneimine) polymer has produced a new type of catalyst that features interesting characteristics.1 The catalyst is very active and also readily recyclable without loss of activity. Unlike Pd on other solid supports, this polymer is soluble in different solvent media and necessitates membrane separation technology for its removal after the desired synthetic conversion is completed. The catalyst is not soluble in water and alcoholic solvents and can be removed by filtration at the end of the reaction.

Hydrogenations.

The catalyst mediates the reduction of 2-pentyne at 20 °C and 0.1 mPa H2 pressure in 40 min to give cis-2-pentene with 98% stereoselectivity. The stereoselectivity and catalyst turnover were cited to be superior to the Lindlar catalyst (Palladium on Calcium Carbonate (Lead Poisoned)). By binding benzonitrile to the Pd on the support, a dramatic change in the reduction of 2-pentyne occurred. The result was the formation of trans-2-pentene selectively.2 The versatility of this catalyst in providing either cis- or trans-alkenes selectively from alkynes has never been demonstrated by any other heterogeneous catalyst. With formic acid as the hydrogen source, transfer hydrogenolysis of the benzyloxycarbonyl (Cbz) protecting group on polypeptides was readily carried out in a mixture of MeOH and H2O at rt.1a The catalyst used in this case was highly cross linked and was insoluble in the MeOH/H2O solvent mixture, and removal of the catalyst by a simple filtration was possible.


1. (a) Coleman, D. R.; Royer, G. P. JOC 1980, 45, 2268. (b) Behr, A. Fett. Wissenschaft Technol. 1990, 92, 375.
2. Bayer, E.; Schumann, W. CC 1986, 949.

Anthony O. King & Ichiro Shinkai

Merck Research Laboratories, Rahway, NJ, USA



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