Cyrene, a bio-based solvent as replacement for NMP, DMF & DMAc

The biobased solvent Cyrene was previous discussed in an article regarding solvents but deserves a little more attention for its unique characteristics. Cyrene is developed by the Australian based Circa group and originates from their platform molecule: Levoglucosanone.

Synthesis and properties of Cyrene

This molecule is produced in a patented process from cellulosic waste material originated from paper production. Currently, the subsequent reduction of the LGO is still done via metal catalysis, although enzymatic options are being explored and seem certain to be used in the future.

 

 

 

 

 

 

Since 2018 Will & Co is supporting the Circa group in distributing this biobased solvent across Europe and recently plans to build a >1000 mt flag-ship plant have been initiated. End of 2022 this plant is fully operational with large quantities of Cyrene becoming available to the market.

Based on its Hansen parameters, Cyrene shows a lot of similarities to reprotoxic solvents such as NMP, DMF and DMAc. For many applications, these solvents already have been banned and it is expected that these can only be used in exceptional circumstances. Opposed to these three reprotoxic solvents, Cyrene has little labelling and is not reprotoxic.

 

	Cyrene	NMP	DMF	DMAc
δD (MPa)1/2	18.8	18.4	17.4	16.8
δP (MPa)1/2	10.6	12.3	13.7	11.5
δH (MPa)1/2	6.9	7.2	11.3	10.2
b.p. (°C)	227	202	153	165
η (mPa·s)*	14.5	1.9	0.9	1.0

 

Already Cyrene has proven itself in replacing these labelled solvents in many applications such as nutraceutical extractions, pharmaceutical synthesis, graphene, polyurethane dispersions and dissolving dyes for example.

Stability of Cyrene

Cyrene is a cyclic ketone and as such is poorly resistant to strong bases. In their presence, it will quickly dimerize, ultimately forming insoluble polymers. Against moderate acids it is stable, observing now effects in trifluoroacetic acid, while strong acids such as 2M HCl result in Cyrene forming a complex mixture of derivatives. Cyrene reacts violently with a 30% hydrogen peroxide solution.

Applications of Cyrene

As a new biobased solvent Cyrene chemistries have not been fully explored yet. It has however shown useful as a drug precursor, a solvent in many chemical reactions such as Sonagashira and Suzuki couplings as well as in amide formations amongst others, as an excellent solvent for graphene dispersions and dye dispersions and in various coating applications.