Unconventional solvents

Grieco P. A. Organic Chemistry in Unconventional Solvents Aldrichimica Acta 1991 24 59-66... 

Further progress in stabilizing highly charged anions was achieved by the appK-cation of unconventional solvents such as ammonia or dimethylamine at low temperatures. Using these solvents it was possible to observe the reversible generation of supercharged anions at low scan rates in voltammetric experiments [34, 35]. 

Grieco, P.A., Organic chemistry in unconventional solvents, Aldrichim. Acta, 1991, 24, 59. 

Polycondensation of diethyl 1,8-octanoic diacid and 1,4-butanediol at room temperature and at 60°C was carried out in l-butyl-3-methylimidazolium hex-afhrorophosphate ionic liquid (see also Chapter 13 for enzymatic polymerizations in unconventional solvents), using lipase PS-C as catalyst [42]. The highest molecular weight polymer (M = 4300 M , = 5400) was obtained at 60 °C for 7 days. 

Less environmentally-damaging solvents range from wisely-chosen conventional solvents to extremely unconventional solvents. Most of the environmental impact reduction that has been achieved in industry from solvent substitution has been by switching to greener conventional solvents. 

Unconventional solvents include supercritical CO2 (scCOiX CO2-expanded liquids, " ionic liquids, fluorous liquids, and liquid polymers. The advantages and disadvantages of each are summarized in Table I. 

Table I. Advantages and Disadvantages of Green Unconventional Solvents...

Y. Gu, Green Chem. 2012, 14, 2091-2128. Multicomponent reactions in unconventional solvents state of the art. 

A greater awareness of the origin of solvents, and why they are suitable for some reactions but not others, will be an essential quality of the future medicinal chemist. They will also need to embrace unconventional solvents in order to continue practicing the reactions familiar to medicinal chem-istiy. Computational tools such as COSMO-RS are available for solvent selection that can improve the understanding and uptake of bio-based solvents. For example, limonene and p-cymene are bio-based solvent substitutes for traditional hydrocarbon solvents. 

This methodology afforded a suitable route to heterocycles, which were mainly prepared through multiple steps requiring long reaction times or harsh conditions. In addition to the use of unconventional solvents, microwave irradiation also allows the possibility of conducting reactions in the solid phase, that is, under solventless conditions. Dandia et al. (2006) reported a microwave promoted synthesis of... 

Similar concerns have also inhibited the adoption of unconventional solvents. Two good examples are supercritical carbon dioxide and two-phase aqueous systems. Supercritical carbon dioxide can be effectively used to decaffeinate coffee. However, its broad adoption has been inhibited by the major capital cost of the equipment. Two-phase... 

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