A highly efficient Ti-catalyst for the deoxygenative reduction of esters under ambient conditions: experimental and mechanistic insights from DFT studies

Bhattacharjee, Jayeeta and Das, Suman and Panda, Tarun K and et al, . (2022) A highly efficient Ti-catalyst for the deoxygenative reduction of esters under ambient conditions: experimental and mechanistic insights from DFT studies. Dalton Transactions, 51 (15). pp. 5859-5867. ISSN 1477-9226

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Abstract

In this paper, we report the synthesis of dianionic amidophosphineborane-supported titanium chloride [{Ph2P(BH3)N}2C6H4TiCl2] (1) and TiIV alkyl complex [{Ph2P(BH3)N}2C6H4Ti(CH2SiMe3)2] (2) using a salt metathesis reaction. TiIV complex 1 was obtained by the reaction of the bis-borane ligand [{Ph2P(BH3)NH}2C6H4] and TiCl4 in toluene followed by the addition of 2 equivalents of [LiN(SiMe3)2] at ambient temperature. TiIV bis-alkyl complex 2 was isolated from the reaction of complex 1 with 2.5 equivalents of LiCH2SiMe3 in toluene. The solid-state structure of complex 1 is established by single-crystal X-ray diffraction analysis. TiIV bis-alkyl complex 2 has proved to be a competent catalyst in the deoxygenative reduction of aliphatic and aromatic esters with pinacolborane (HBpin) to afford corresponding boryl ethers at room temperature under solvent-free conditions. Catalyst 2 exhibits chemoselectivity toward ester functionalities over halides, heteroatoms, olefins, and amino functional groups. DFT studies demonstrate that the active form of catalyst 2 is capable of easily transferring its hydrides to ester substrates at room temperature. The studies further reveal that the rate-limiting step (RLS) in an ester-to-boryl ether conversion is the cleavage of the C-O bond of an ester. In brief, the titanium-catalysed ester-to-boryl ether conversions are found to be downhill processes having small activation barriers along all mechanistic steps. © 2022 The Royal Society of Chemistry.

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IITH Creators:

IITH Creators	ORCiD
Panda, Tarun K	http://orcid.org/0000-0003-0975-0118

Item Type:

Article

Additional Information:

Financial support for this work was given by the Science and Engineering Research Board (SERB), India, under project no. EMR/2016/005150. J. B. thanks the UGC and A. H. thanks the CSIR India for their respective Ph.D. fellowships. The authors thank the Department of Chemistry, Indian Institute of Technology (IIT) Hyderabad for the equipment facility. PR thanks the CSIR for the SRF fellowship (09/143(1001)/2019-EMRI). PG acknowledges the SERB (CRG/2021/000759) for financial support and the IIT Roorkee for computational lab facility.

Uncontrolled Keywords:

% reductions; Alkyl complexes; Ambient conditions; Complex 1; DFT study; Mechanistics; Metathesis reactions; Salt metathesis; Solid-state structures; ]+ catalyst

Subjects:

Chemistry

Divisions:

Department of Chemistry

Depositing User:

. LibTrainee 2021

Date Deposited:

22 Jul 2022 06:51

Last Modified:

22 Jul 2022 06:51

URI:

http://raiithold.iith.ac.in/id/eprint/9561