Gel capsules make reactions with organolithiums simpler and safer
Low-cost gels have improved the stability of organolithium reagents, making manipulation simple and safe. Thanks to this innovative encapsulation method, these reactive compounds – usually sensitive to moisture and air – survive storage under ambient conditions for over 25 days. Moreover, these gel capsules work with other organometallic reagents, such as Grignards, hinting at additional attractive applications protecting pyrophoric compounds and hazardous chemicals.
Organic chemists have used organolithium reagents for over a century. Versatile and highly reactive, these organometallic species have become a fundamental tool for synthesis across different disciplines. However, handling them presents problems – organolithiums often need controlled conditions, such as inert atmospheres and cryogenic temperatures. ‘For many years, I had seen [my colleague] Peter O’Brien working with organolithiums, and had been impressed by the high levels of technical skill involved,’ explains David Smith, from the University of York, who co-led this study. ‘After attending a fascinating seminar from Eva Hevia, [who had used deep eutectic solvents] to stabilise organolithium reagents, I wondered whether we could do something similar with our gels,’ he says.
Gels are three-dimensional polymers. In contact with solvents, they become soft, jelly-like materials that retain their cross-linked structure, offering different functionalities. In this case, the team used a cheap hexatriacontane (C36H74) organogel. ‘We took a standard solution of the organolithium reagent in a mould, and added the gelator,’ explains Smith. After gentle heating and cooling, the gel is ready to unmould and use. Among the advantages, researchers can cut the organolithium gels into smaller pieces with scissors or razorblades, which could speed up screening studies. ‘The homogeneous distribution of the organolithium within the gel simply results from the [production] process,’ says Smith. ‘[Scientists] elsewhere have reproduced the methods, and they found the gels stable and easy to handle.’
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