GREEN CHEMISTRY
a b formation . This indicates improved recyclability and applicability to oxidation reactions .
MTHP is also stable in acids and basic media , and can be used in various reactions and work-up processes . Another interesting feature is that n-butyl lithium ( n-BuLi ) is relatively stable in MTHP , making it a good solvent for various organometallic reactions . c
< Esterification >
� C02H + <:r OH z nc 12 0 _ . 1 m _ ol 0 Yo ___
V V MTHP
Yield (%) 97
< Acetalisation >
V
Yield (%) 99
CHO + azeotropic anhydration 25h
Impurity of hydrolysis Not detected
TsOH 1mol %
MTHP azeotropic anhydration 2h
Impurity of hydrolysis Not detected
0
Purity of recovery MTHP > 99.9 %
Purity of recovery MTHP > 99.9 % azeotrope ( oc ) composition
MTHP 85 81 / 19 ( water )
Toluene 85 80 / 2o ( water )
Figure 5 – Grignard reaction ( a ), oxidation ( b ) & esterification & acetalisation ( c ): MTHP v alternative solvents
Applications of MTHP
MTHP not only has excellent stability but is also applicable to various different reactions . Figure 5a shows an example of Grignard reagent preparation using chlorohexane as a substrate .
THF is widely used as a solvent in the preparation of Grignards , but it has a boiling point of 66 ° C . Therefore , the temperature cannot be raised any higher at atmospheric pressure . In this example , the reaction did not proceed at 66 ° C because the temperature was not high enough .
MTHP has a boiling point of 105 ° C , allowing reactions to be conducted at higher temperatures than with THF . Grignard reagent preparation from chlorohexane proceeded by performing the reaction at 90 ° C in MTHP and
Figure 6 – Process improvements using MHTP the target product was obtained at a high yield .
As mentioned above , MTHP has high oxidation stability and can be used as a solvent in oxidation reactions . As shown in Figure 5b , the target product is obtained at a good yield . Halogenated solvents such as dichloromethane are often used in oxidation reactions , but their toxicological profile is an issue , making MTHP an obvious alternative
Due to its high stability in acidic mediums , MTHP can be used in reactions involving azeotropic dehydration in the presence of acids , such as esterification and acetalisation ( Figure 5c ). Toluene is often used for azeotropic dehydration , but it is highly toxic . MTHP has a similar azeotropic temperature and azeotropic
composition with water to toluene , so it can be a good alternative
All of these series of reactions can also be carried out with MTHP as the only solvent in the entire process . Figure 6 shows model test results . In the conventional method , the solvent used in each process is different , so solvent substitution is necessary and can result in complicated operations . Fortunately , MTHP can be used as the solvent for all three processes . The target product is obtained at high yield without solvent substitution , which is a significant process improvement .
Conclusion
Kuraray is committed to developing new fields of business using pioneering technology that improves the environment and enhances the quality of life throughout the world . MTHP is one of the company ’ s products that can greatly contribute , as a solvent , to achieving greener chemistry . ●
Yuusuke Saitou
KURARAY k + 81 254 43 5190 J yuusuke . saitou @ kuraray . com j www . kuraray . com
32 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981