Efficient synthesis of 19–31 membered macrocyclic tetralactones via ring closing metathesis in ionic liquids

The ring closing metathesis reaction in the presence of Grubbs catalyst was demonstrated using several ionic liquids to synthesize a range of macrocyclic tetralactones having ring size of 19 to 31 membered with different spacers. The ionic liquid [mmim][PF6] was found to be an excellent solvent and the recovery of the catalyst was demonstrated. X-ray analysis of a representative macrocyclic tetralactone was also reported.