The Effect of Alkyl Substituents on the Formation and Structure of Homochiral (<i>R</i>*,<i>R</i>*)-[R<sub>2</sub>Ga(<i>µ</i>-OCH(Me)CO<sub>2</sub>R′)]<sub>2</sub> Species—Towards the Factors Controlling the Stereoselectivity of Dialkylgallium Alkoxides in the Ring-Opening Polymerization of <i>rac</i>-Lactide

The Effect of Alkyl Substituents on the Formation and Structure of Homochiral (<i>R</i>,<i>R</i>)-[R<sub>2</sub>Ga(<i>µ</i>-OCH(Me)CO<sub>2</sub>R′)]<sub>2</sub> Species—Towards the Factors Controlling the Stereoselectivity of Dialkylgallium Alkoxides in the Ring-Opening Polymerization of <i>rac</i>-Lactide

Building on our previous studies, which have demonstrated that homochiral propagating species—(<i>R</i>*,<i>R</i>*)-[Me<sub>2</sub>Ga(<i>µ</i>-OCH(Me)CO<sub>2</sub>R)]<sub>2</sub>—were crucial for the heteroselectivity of [Me<...

Full description

Saved in:

Bibliographic Details
Main Authors:	Magdalena Kaźmierczak, Łukasz Dobrzycki, Maciej Dranka, Paweł Horeglad
Format:	Article
Language:	English
Published:	MDPI AG 2025-01-01
Series:	Molecules
Subjects:	biodegradable polyesters polylactide tacticity heterotactic dimers diastereomers
Online Access:	https://www.mdpi.com/1420-3049/30/1/190
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	Building on our previous studies, which have demonstrated that homochiral propagating species—(<i>R</i>,<i>R</i>)-[Me<sub>2</sub>Ga(<i>µ</i>-OCH(Me)CO<sub>2</sub>R)]<sub>2</sub>—were crucial for the heteroselectivity of [Me<sub>2</sub>Ga(<i>µ</i>-OCH(Me)CO<sub>2</sub>Me)]<sub>2</sub> in the ring-opening polymerization (ROP) of racemic lactide (<i>rac</i>-LA), we have investigated the effect of alkyl groups on the structure and catalytic properties of dialkylgallium alkoxides in the ROP of <i>rac</i>-LA. Therefore, we have isolated and characterized the <i>rac</i>-[R<sub>2</sub>Ga(<i>µ</i>-OCH(Me)CO<sub>2</sub>Me]<sub>2</sub> (R = Et (<b>1</b>), <i><sup>i</sup></i>Pr (<b>2</b>) and <i>rac</i>-[R<sub>2</sub>Ga(<i>µ</i>-OCH(Me)C<sub>5</sub>H<sub>4</sub>N]<sub>2</sub> (R = Et (<b>3</b>), <i><sup>i</sup></i>Pr (<b>4</b>)) complexes, to demonstrate the effect of alkyl groups on the chiral recognition induced the formation of the respective homochiaral species—(<i>R</i>,<i>R</i>)-[R<sub>2</sub>Ga(<i>µ</i>-OCH(Me)CO<sub>2</sub>Me)]<sub>2</sub> and (<i>R</i>,<i>R</i>)-[R<sub>2</sub>Ga(<i>µ</i>-OCH(Me)C<sub>5</sub>H<sub>4</sub>N]<sub>2</sub>. Moreover, we have investigated the structure of (<i>S</i>,<i>S</i>)-[R<sub>2</sub>Ga(<i>µ</i>-OCH(Me)CO<sub>2</sub>Me]<sub>2</sub> (R = Et ((<i>S</i>,<i>S</i>)-<b>1</b>, R = <i><sup>i</sup></i>Pr ((<i>S</i>,<i>S</i>)-<b>2</b>,) and their catalytic activity in the ROP of <i>rac</i>-LA. With an increase in the bulkiness of alkyl substituents on gallium the following can be observed: (a) the tendency for the formation of homochiral complexes decreased, (b) the symmetry of homochiral (<i>S</i>,<i>S</i>)-[R<sub>2</sub>Ga(<i>µ</i>-OCH(Me)CO<sub>2</sub>Me]<sub>2</sub> (M = Me, Et (<i>S</i>,<i>S</i>)-<b>1</b>), <i><sup>i</sup></i>Pr (<i>S</i>,<i>S</i>)-<b>2</b>) changed, and both have resulted in (c) lower or no heteroselectivtity across these complexes in the ROP of <i>rac</i>-LA. Importantly, the results have confirmed the crucial role of the chiral-induced formation of homochiral asymmetric dimers on the heteroselectivity of dialkylgallium alkoxides in the ROP of <i>rac</i>-LA.
ISSN:	1420-3049