Heck reactions performed on enones usually result in a mixture, of the expected Heck product and the reduced Heck product (formally, the conjugate addition product). This results from two possible pathways a s �alkyl Pd complex can follow upon migratory insertion into an alkene, namely �-hydride elimination and reductive cleavage (Scheme1).In this poster communication, two cases are presented in which the reaction conditions are modified effectivily to afford either the Heck product or the conjugate addition product selectively. In the first section, a discussion about Pd(OAc)2-BIAN (Bisaryl-acenapthaquinonediimine) is presented.  Pd(OAc)2-BIAN was found to be an excellent catalyst for the base-free oxidative Heck reaction, in which molecular oxygen is the sole oxidant,. The system was found to be selective for the formation of the expected Heck product, while phenol and biphenyl were detected only in trace quantities (Scheme2).In the second section, selectivity between conjugate addition and the Mizoroki-Heck reaction is discussed, in the addition of iodoarenes. Herein, a novel catalyst system is presented, which by mere choice of the base, affords the conjugate addition or the Mizoroki-Heck product selecitively. Only 1.5 mol% of a commerically available Pd-carbene is required for this procedure, and the system has been shown to be applicable for a variety of linear and cyclic enones. Further, these reactions can be performed conveniently under microwave irradiation, without loss of yields or selectivity.

Selectivity in palladium catalyzed transformations of enones: The oxidative-Heck reaction and conjugate addition of Iodoarenes

243rd National Meeting (2012)

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