Efficient Synthesis of 6-(1H-1,2,4-Triazol-1-yl)-thieno[2,3-d]pyrimidin-4(3H)-ones via an Iminophosphorane

Abstract

Ethyl 2-amino-4-methyl-5-(1H-1,2,4-triazol-1-yl)thiophene-3-carboxylate 2, obtained from Gewald reaction of 1-(1H-1,2,4-triazol-1-yl)acetone 1 with ethyl cyanoacetate and sulfur, was transferred into iminophosphorane 3. Further reaction of 3 with aromatic isocyanates gave carbodiimides 4, which were treated subsequently with a secondary amine to give 6-(1H-1,2,4-triazol-1-yl)-thieno[2,3-d]pyrimidin-4(3H)-ones 6 in good yields in the presence of a catalytic amount of sodium ethoxide.

Keywords:

• Aza-Wittig reaction
• Gewald reaction
• iminophosphorane
• thieno[2,3-d]pyrimidin-4(3H)-one
• 1,2,4-triazole

ACKNOWLEDGMENTS

We gratefully acknowledge financial support of this work by the National Natural Science Foundation of China (Project Nos. 20672041 and 20772041), the Key Project of Chinese Ministry of Education (No. 107082), and the Science Foundation of Hubei Education Commission of China (Project No. Q20086001).

Notes

^a Isolated yields based on iminophosphorane 3.