Synthesis of Di- and Tri-Substituted Imidazole-4-carboxylates via PBu₃-Mediated [3 + 2] Cycloaddition

Abstract

Some new di- and trisubstituted imidazole-4-carboxylates were prepared from amidoacetic acids 3 in the present report. The key step to establish such imidazole-4-carboxylates stemmed from the PBu₃-mediated [3 + 2] cycloaddition between in situ–generated Δ2-oxazolinone 4 and ethyl cyanoformate6. Our results indicated that trisubstituted imidazoles 7–20 were afforded in better yields than those of disubstituted imidazoles 21–27.

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GRAPHICAL ABSTRACT

Keywords:

• [3 + 2] Cycloaddition
• cyclo-dehydration
• dehydrating agent
• imidazole-4-carboxylate
• Δ2-oxazolinone

ACKNOWLEDGMENT

Financial support from the National Science Council of the Republic of China to A. Y. S. is gratefully acknowledged.

Notes

^a Yield refers to two-step isolated 7 from amidoacetic acid 3a.

^b The product was not found.

^a One-pot, two-step isolated yield.