The final answer probably depends on requirements/limitations for the solvent (under reduced pressure?) you are looking for. Alkyl derivatives of quinoline, for example, should have higher b.p. (less harmful?), fit your similarity criteria, but may not be available (commercially).

I had similar problems in solvent search regarding b.p. and viscosity. The ThermoML Archive is a rich open-access resource with solvent and solvent-mixture properties (pressure-temperature data) ready to be screened and filtered. However, I haven't found any good software interface that specifically target such tasks in connection with ThermoML. Further, ThermoML doesn't use SMILES yet (no molecular similarity search possible), although included in the ThermoML Schema. I also would be interested to know, if there is something out there? (For my own work, I have a few crude algorithms.)

Thank you very much for your answer. I will look at that web of ThermoML. Also the derivatization of quinoline is an interesting approach I hadn't considered... I will try to do a search of possibilities.

I have found some oligoethylenethers with b.p. over 200ºC and could be easily removed by washing with with water (since my product is not polar) but I should check if the reaction could work in this solvents.

Maybe a silicon oil (with or without phenyl functional groups) could match the target. These oils are stable at temperature up to 300°C. I used them as solvents for some organic reaction of polyurethane polymerization where these oils matched also as flowing agent

It’s well known that the ionic liquids have the highest boiling points with no hazards. So you have to select the suitable ionic liquid for your reaction in order to make it faster and get an excellent yield. Because the right selected ion liquid gives no byproducts as well as it is work as a catalyst.

Dear Mr. Diaz-Moscoso

You may use ehtylene glycol as that is a good heat convecting medium and boiling point is quite high. You may see my papers also.

Article Synthesis of Cu1.8S and CuS from Copper-Thiourea Containing ...

Thank you very much everybody for all these valuable information.

I didn't mention that y reaction involve strong bases apart from the high temperature. For that reason some solvents commented here couldn't be used (protic solvents as alcohols or solvents with carbonil groups should be avoided because they could react and remove the base from the reaction).

I think that the oligo methylethers (like diglyme or longer analogues) is still the best option.

For your applicationI suggest you to try something similar to a solvent that is used in polymers as flowing agents, common name is plasticizers as i.e Dioctylphtalate http://chemicalland21.com/industrialchem/plasticizer/DOP.htm

these have high boiling point and are often viscous liquids.

Here a list from wikipedia of common plasticizers used in polymers technology

Dicarboxylic/tricarboxylic ester-based plasticizers

Phthalate-based plasticizers are used in situations where good resistance to water and oils is required. Some common phthalate plasticizers are:

Bis(2-ethylhexyl) phthalate (DEHP), used in construction materials and medical devices

Diisononyl phthalate (DINP), found in garden hoses, shoes, toys, and building materials

Bis(n-butyl)phthalate (DnBP, DBP), used for cellulose plastics, food wraps, adhesives, perfumes, and cosmetics - about a third of nail polishes, glosses, enamels, and hardeners contain it, together with some shampoos, sunscreens, skin emollients, and insect repellents

Butyl benzyl phthalate (BBzP) is found in vinyl tiles, traffic cones, food conveyor belts, artificial leather, and plastic foams

Diisodecyl phthalate (DIDP), used for insulation of wires and cables, car undercoating, shoes, carpets, pool liners

Di-n-octyl phthalate (DOP or DnOP), used in flooring materials, carpets, notebook covers, and high explosives, such as Semtex. Together with DEHP it was the most common plasticizers, but now is suspected of causing cancer

Diisooctyl phthalate (DIOP), all-purpose plasticizer for polyvinyl chloride, polyvinyl acetate, rubbers, cellulose plastics, and polyurethane.

Diethyl phthalate (DEP)

Diisobutyl phthalate (DIBP)

Di-n-hexyl phthalate, used in flooring materials, tool handles, and automobile parts

Trimellitates are used in automobile interiors and other applications where resistance to high temperature is required. They have extremely low volatility.

Trimethyl trimellitate (TMTM)

Tri-(2-ethylhexyl) trimellitate (TEHTM-MG)

Tri-(n-octyl,n-decyl) trimellitate (ATM)

Tri-(heptyl,nonyl) trimellitate (LTM)

n-octyl trimellitate (OTM)

Adipate-based plasticizers are used for low-temperature or resistance to ultraviolet light. Some examples are:

Bis(2-ethylhexyl)adipate (DEHA)

Dimethyl adipate (DMAD)

Monomethyl adipate (MMAD)

Dioctyl adipate (DOA)

Sebacate-based plasticiser

Dibutyl sebacate (DBS)

Maleates

Dibutyl maleate (DBM)

Diisobutyl maleate (DIBM)

[edit]Other plasticizers

Benzoates

Epoxidized vegetable oils

Sulfonamides

N-ethyl toluene sulfonamide (o/p ETSA), ortho and para isomers

N-(2-hydroxypropyl) benzene sulfonamide (HP BSA)

N-(n-butyl) benzene sulfonamide (BBSA-NBBS)

Organophosphates

Tricresyl phosphate (TCP)

Tributyl phosphate (TBP)

Glycols/polyethers

Triethylene glycol dihexanoate (3G6, 3GH)

Tetraethylene glycol diheptanoate (4G7)

Polymeric plasticizers

Polybutene

Some other chemicals working as plasticizers are nitrobenzene, carbon disulfide and β-naphthyl salicylate. Plasticizers, such as DEHP and DOA, were found to be carcinogens and endocrine disruptors.

[edit]Safer plasticizers

Safer plasticizers with better biodegradability and fewer biochemical effects are being developed. Some such plasticizers are:

Acetylated monoglycerides; these can be used as food additives

Alkyl citrates, used in food packagings, medical products, cosmetics and children toys

Triethyl citrate (TEC)

Acetyl triethyl citrate (ATEC), higher boiling point and lower volatility than TEC

Tributyl citrate (TBC)

Acetyl tributyl citrate (ATBC), compatible with PVC and vinyl chloride copolymers

Trioctyl citrate (TOC), also used for gums and controlled release medicines

Acetyl trioctyl citrate (ATOC), also used for printing ink

Trihexyl citrate (THC), compatible with PVC, also used for controlled release medicines

Acetyl trihexyl citrate (ATHC), compatible with PVC

Butyryl trihexyl citrate (BTHC, trihexyl o-butyryl citrate), compatible with PVC

Trimethyl citrate (TMC), compatible with PVC

alkyl sulphonic acid phenyl ester (ASE), compatible with PVC , vinyl chloride copolymers, TPU, NBR etc.

1,2-Cyclohexane dicarboxylic acid diisononyl ester (BASF trademark: DINCH) is used in food packaging, medical devices, toy and childcare articles. It is compatible with a wide range of polymers including PVC.

• Triphenylmethan, 519-73-3, bp 358; 1 €/g

• Biphenyl 92-52-4, bp 255 °C, 0.05 €/g, reizend

These two have both a very high boiling point and have no functional groups, which could be attacked. Furthermore they can be detected very easily due to the aromats.

Depending on what polarity you need is another consideration. diphenyl ether (bp~257 C) or octadecene (bp 315 C) are some suggestions.