Microwave-Accelerated Ruthenium-Catalyzed [2π + 2π] Cycloadditions of Dimethylacetylene Dicarboxylate with Norbornenes

Abstract

An efficient and convenient procedure has been developed for the ruthenium-catalyzed [2π + 2π] cycloadditions of dimethylacetylene dicarboxylate with norbornenes. Reaction is significantly accelerated in microwave conditions, while the commonly used benzene solvent was replaced by environmentally benign tetrahydrofuran.

Keywords:

• Acetylenes
• [2 + 2] cycloadditions
• microwave reaction
• norbornene derivatives

ACKNOWLEDGMENTS

This research was funded by grants from the Croatian Ministry of Science, Education, and Sport (Nos. 098-0982933-3218 and 098-0982933-2920) and the Croatian Academy of Arts and Sciences.

Notes

^a Standard reaction conditions: DMAD (1.2 equiv), Ru catalyst (0.1 equiv), dry THF (0.5 mL), 80 °C, 1 h. Literature procedure: DMAD (2–5 equiv), Ru catalyst (0.2–0.5 equiv), dry benzene, 80 °C, 24 h, 67%.

^b Variation of standard conditions.

^a Standard reaction conditions: DMAD (1.2 equiv), Ru catalyst (0.1 equiv), dry THF (0.5 mL), 80 °C, 1 h.

^b Variation of standard conditions.

^c Literature procedure: dry benzene, 80 °C, 1–4 days.

^d Yields for products 3/4/22.

^e Only product 3 was obtained.