Title:Microwave Induced Preparations of Incipient and Solvent Stabilized Cyclopentadiene for Diels-Alder Reactions with Kinetic Control
Volume: 2
Issue: 2
Author(s): J. Michael Robinson, Kristina A. Chang, Chelsey C. Gorter, Mary E. Kincade, Ashley N. Pinson, Marisa P. Ramos, Rachel F. Ramos, Mark D. Reno, Christopher J. Valenzuela, Tatiana Vidal, Marcus W. Worden and Virginia R. Zamudio
Affiliation:
Keywords:
1H NMR, acetone, biotage Initiator +, cis-endo-5-norbornene-2, 3-dicarboxylic anhydride, cis-exo-5-norbornene-
2, 3-dicarboxylic anhydride, cyclopentadiene, dicyclopentadiene, Diels-Alder, maleic anhydride, maleimide, microwave, Nmethylmaleimide,
N-phenylmaleimide, reaction severity, solvent stabilization.
Abstract: A microwave induced reaction of dicyclopentadiene (1) was used to rapidly and conveniently
generate cyclopentadiene (2) which is stabilized in a polar solvent for subsequent use. In this
case 2 was used for Diels-Alder reactions at ambient temperature. A 3 min microwave induced reaction
of 1 in acetone gave a solution of 2, followed by a room temperature reaction with a limited
amount of a highly active dienophile, maleic anhydride (3), which afforded pure cis-endo-5-
norbornene-2,3-dicarboxilic anhydride (4). Simultaneous reactions were achieved in 0.5 min at 200°C
but some of the exo-isomer 5 also resulted. Several maleimides also demonstrated the convenient utility
of these microwave methods for reactions of 2 for valuable industrial compounds. This method now precludes the previous
arduous thermal cracking of 1 along with the simultaneous fractional distillation of 2.