The disclosure provides, inter alia, safe and environmentally-friendly methods, such as flow chemistry, to synthesize isocyanates, such as methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and tetramethylxylene diisocyanate.

The present invention provides bio-based aromatic diisocyanate of formula (I). [Formula should be inserted here] wherein X is OCH.sub.3, Y is selected from —H or OCH.sub.3, and m=0-12. The present invention further provides a method for preparation of aromatic diisocyanate of formula (I) useful for preparation of polyurethane.

##STR00001##

The present invention provides bio-based aromatic diisocyanate of formula (I). [Formula should be inserted here] wherein X is OCH.sub.3, Y is selected from —H or OCH.sub.3, and m=0-12. The present invention further provides a method for preparation of aromatic diisocyanate of formula (I) useful for preparation of polyurethane.

##STR00001##

A difunctional biphenyl compounds corresponding to formula (I) ##STR00001##
wherein Alk, Alk′ and R are as defined in the description. These compounds are suitable as hardeners for thermosetting resins, especially epoxy resins.

A synthesis method for a candesartan cilexetil intermediate represented by formula (II) is provided. The method includes (1) dissolving a compound represented by formula (IV) to an aprotic solvent to obtain a first mixed solution, and dissolving a phase transfer catalyst and an azidation reagent to water to obtain a second mixed solution; (2) dropping the first mixed solution to the second mixed solution for azidation reaction, and after the reaction is ended, standing and layering same to obtain an organic phase containing a compound represented by formula (V); (3) dropping the obtained organic phase containing the compound represented by formula (V) to tertiary butyl alcohol for rearrangement reaction, and after the reaction is ended, concentrating same to obtain a solid or oily material, then adding a crystallizing solvent to the obtained solid or oily material for recrystallization, and separating same to obtain a crystal.

A difunctional biphenyl compounds corresponding to formula (I)

##STR00001##

wherein Alk, Alk and R are as defined in the description. These compounds are suitable as hardeners for thermosetting resins, especially epoxy resins.

The present invention provides bio-based aromatic diisocyanate of formula (I). [Formula should be inserted here] wherein X is OCH.sub.3, Y is selected from H or OCH.sub.3, and m=0-12. The present invention further provides a method for preparation of aromatic diisocyanate of formula (I) useful for preparation of polyurethane. ##STR00001##

The present invention provides bio-based aromatic diisocyanate of formula (I). [Formula should be inserted here] wherein X is OCH.sub.3, Y is selected from H or OCH.sub.3, and m=0-12. The present invention further provides a method for preparation of aromatic diisocyanate of formula (I) useful for preparation of polyurethane. ##STR00001##