Biomimetic Aerobic CH Olefination of Cyclic Enaminones at Room Temperature: Development toward the Synthesis of 1,3,5‐Trisubstituted Benzenes

Abstract

A green and mild protocol for the dehydrogenative olefination of cyclic enaminones was devised via palladium catalysis at room temperature using oxygen as the terminal oxidant. The synthetic utility of the olefinated cyclic enaminones afforded a series of unique 1,3,5-trisubstituted benzenes via an unanticipated Diels-Alder tandem reaction. The broad substrate scope and good yields achieved with this new protocol provide an alternative pathway for arene functionalization.

Oxidative Coupling between Two Hydrocarbons: An Update of Recent C–H Functionalizations

“…Recently, the reaction condition of enaminones 174 has been further optimized by using a biomimetic aerobic process with catalytic amount of Cu(OAc) 2 and catechol as the electron transfer mediators (Scheme 89). 137 The coumarin then was further applied to couple with acrylates and styrenes by Hong and co-workers. 138 In this case, Pd(OPiv) 2 was used as the catalyst precursor, and O 2 (1 atm) was used as the sole oxidant.…”

Chemistry of Ketene N,S-Acetals: An Overview

“…Ketene N , S -acetals, which possess structural features that enable the olefinic linkage to be activated by electron-releasing alkylthio and amino groups through p−π conjugation, are more reactive toward electrophiles than ethylene. Functionalized ketene N , S -acetals, for example C , having structural features of polarized α-oxo ketene S , S -acetals − ,− and enaminones (Figure ), − have proved to be particularly useful intermediates in organic synthesis. In addition, the incorporation of multiple reactive sites as in enaminones and ketene S , S -acetals, including a good leaving group (alkylthio group) in ketene N , S -acetals along with varied sorts of functional groups (FGs) on the carbon atom adjacent to the acetal moiety (also known simply as the acceptor end) and N -alkyl or N -aryl group, gives ketene N , S -acetals rise to a variety of chemical transformations and allows them to be used easily in the construction of a wide variety of heterocycles. ,,− …”

Palladium‐Catalyzed Domino Dehydrogenation/Heck‐Type Reactions of Carbonyl Compounds

“…(13] [46] is consistent with the DHR of chromones with arenes, [47] -of chromanones and dihydroquinolin-4-ones [Eq. ( 15)] with acrylates is consistent with the DHR of chromones [48] dihydropyranones, [49] quinolones [50] and cyclic enaminones [51] with acrylates, -1,3-dimethyldihydropyrimidine-2,4(1H,3H)-dione [Eq. ( 16)] is consistent with the DHR of uracils with acrylates.…”