Issue 16, 2023

A palladium complex of a macrocyclic selenium ligand: catalyst for the dehydroxymethylation of dihydroxy compounds

Abstract

This report describes the synthesis of a seventeen-membered macrocyclic ring containing ligand (L1) by the reaction of 1,8-bis(2-(chloromethyl)phenoxy)octane with selenium powder. The trans-palladium dichloride complex (C1) of the macrocyclic selenium ligand was synthesized from its reaction with the Pd(CH3CN)2Cl2 precursor. The formation of the ligand and complex was authenticated with the help of various analytical techniques like 1H and 13C{1H} NMR, HRMS, FTIR, UV-visible spectroscopy, and elemental analysis. The structure of the ligand and its coordination mode with the palladium precursor were authenticated with the help of single crystal X-ray diffraction. The complex possesses a distorted square planar geometry around the palladium center. The new ligand and complex are air and moisture insensitive and stable at room temperature for over three months. The variable temperature NMR data and computational studies suggest selenium inversion in the palladium complex (C1) with an inversion barrier of ∼22.6 kcal mol−1. The palladium complex C1 was used as a catalyst for the dehydroxymethylation of long alkyl chain containing dihydroxy compounds. Generally, two separate catalysts are used for dehydroxymethylation (one for the oxidation of the alcohol and the other for the decarbonylation of the aldehyde). Here a single catalyst shows the dual action of dehydroxymethylation with up to 91% yield under only 5.0 mol% catalyst loading. A broad substrate scope can be achieved with good functional group tolerance. The PPh3 and Hg poisoning tests suggest the homogeneous nature of the reaction. Interestingly, the same long alkyl chain containing dihydroxy compounds were reported to undergo macrolactonization when reacted with a ruthenium catalyst.

Graphical abstract: A palladium complex of a macrocyclic selenium ligand: catalyst for the dehydroxymethylation of dihydroxy compounds

Supplementary files

Article information

Article type
Paper
Submitted
06 Feb 2023
Accepted
07 Mar 2023
First published
08 Mar 2023

Dalton Trans., 2023,52, 5110-5118

A palladium complex of a macrocyclic selenium ligand: catalyst for the dehydroxymethylation of dihydroxy compounds

S. Kumar, S. Singh, S. Mahala, P. Janjani, S. Rajagopala Reddy, T. Rom, A. K. Paul, P. Roy and H. Joshi, Dalton Trans., 2023, 52, 5110 DOI: 10.1039/D3DT00375B

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