An efficient protocol is reported for the one‐pot three‐component Bignelli synthesis of a series of 3,4‐dihydropyrimidine‐2(1H)‐ones and thiones in good yields (66–90%) from the aldehydes (4‐benzyloxybenzaldehyde, 5‐bromovanilin, 4‐formyl‐1‐cyclohexene, and trans‐cinnamaldehyde), β‐keto esters (ethyl acetoacetate, allyl acetoacetate, and t‐butyl acetoacetate), and urea/thiourea in ethanol, using nickel chloride hexahydrate as a catalyst.
The advanced organic chemistry experiments
describe the preparation
of fused six-membered lactams to isoxazole and isoxazoline by employing
Ugi four-component reaction (U-4CR) and intramolecular nitrile oxide
cyclization (INOC) synthetic sequence. The experiments were carried
out in 28 h (overnight for U-4CR) and 2 h (for INOC) using commercially
available starting materials. The two-step reaction involves the in situ imine formation in the one-pot multicomponent reaction
and in situ nitrile oxide formation in the INOC.
The experiments are useful in the organic chemistry curriculum for
the introduction of a one-pot multicomponent reaction and 1,3-dipolar
cycloaddition reactions.
Biologically important 12 new important 3,4‐dihydropyrimidin‐2‐(1H)‐ones (‐thiones) were synthesized with in one‐pot three‐component Biginelli reaction from the corresponding aromatic aldehydes (5‐methyl‐2‐thiophenecarboxaldehyde and 2‐chloro‐5‐nitrobenzaldehyde), β‐keto esters (ethylacetoacetate, allylacetoacetate, and t‐butylacetoacetate), and urea/thiourea in the presence of catalytic amount of magnesium bromide and magnesium chloride hexahydrate as nontoxic, inexpensive, and easily available catalysts under solvent‐free conditions at 80 and 100°C. Compared with the catalyst‐free three‐component Biginelli reaction conditions, this method consistently has the advantage of short reaction time (45–100 min) and good to excellent yields (75–91%).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.