Michael additions of dihydropyrimidines and 2-amino-1,3,4-thiadiazoles to α,β-ethylenic compounds: using polyethylene glycols as a green reaction media

Polyethylene glycol (PEG) was found to be an inexpensive, non-toxic, and effective medium for the Michael additions of 3,4-dihydropyrimidines to α,β-ethylenic compounds to provide N3-functionalized dihydropyrimidines in the presence of K2CO3 as the catalyst. Under similar reaction conditions, 2-amino-5-aryloxymethyl-1,3,4-thiadiazoles reacted with methyl acrylate to give unexpected products 5H,6H-[1,3,4]thiadiazolo[1,2-a]pyrimidine-7-ones through tandem Michael addition and intramolecular cyclization.