Synthesis of Bicyclo[4.3.0]Non-3-ene-7,9-diones via Solventless Diels–Alder Methodology

Abstract

Four novel bicyclo[4.3.0]non-3-ene-7,9-diones have been synthesized in moderate to good yields through a solventless Diels–Alder cycloaddition method and characterized. Atom economies after purification ranged from 21% to 32%, and E factors ranged from 2.7 to 3.7. All reaction products exhibited endo selectivity. Dienophiles with heteroatoms that contribute electrons to the π system exhibited faster reaction times than the carbocyclic analog. Hydrogen-bond donating ability in the diene had no noticeable effect on reaction times.

Keywords:

• Bicyclo[4.3.0]
• Diels–Alder
• green chemistry
• solventless reactions

ACKNOWLEDGMENTS

The Mass Spectrometry Laboratory at the University of Illinois–Urbana/Champaign provided high-resolution mass spectra. NMR Analysis and Consulting of Decatur, Illinois, provided high-field NMR spectra. The FTIR spectrophotometer was acquired with partial funding from a 2008 Pittsburgh Conference Memorial National College Grant. The authors thank Dr. Clarence Josefson for performing MO energy calculations.

Notes

^a Although not formally a reactant, the rinse solvent was included in the calculation of atom economy.

^b Ref. 19.