Palladium(0)-Catalyzed Difunctionalization of 1,3-Dienes: From Racemic to Enantioselective

Abstract

1,3-Dienes are easily accessible chemicals that participate in a series of reactions acting on the carbon–carbon double bonds. Catalytic difunctionalization of 1,3-dienes provides a wide scope of functionalized chemicals. Pd(0) catalysts provide a diverse set of principles for the creation of asymmetric catalytic reactions, which are initiated with the oxidative addition and then undergo insertion reaction with one of double bonds of the 1,3-diene to become a π-allyl palladium species that is reactive toward nucleophilic attack. This review summarizes typical advances on the Pd(0)-catalyzed difunctionalization of 1,3-dienes in recent decades, particularly emphasizing the concepts that enable the switch from a racemic reaction to an enantioselective version.1 Introduction2 Amination3 Boration4 Carbonation5 Hydrogenation6 Oxygenation7 Silylation8 Conclusion and Outlook

Catalytic radical generation of π-allylpalladium complexes

“…In general, tertiary, secondary and primary acids were all compatible and the corresponding products could be obtained in good to excellent yields. 15 (14) were all compatible in this radical cross-coupling reaction. In all the cases, the products were obtained in excellent yields, with complete stereo-and regiocontrol.…”

“…13 Additionally, -allylpalladium complexes can be formed through oxidative addition of a Pd(0) species into an aryl or vinyl halide followed by migratory insertion into a 1,3-diene. [14][15][16][17] Methods for the generation of -allylpalladium complexes from alkyl halides or analogous electrophiles using Pd(0) (for the formation of C(sp 3 )-C(sp 3 ) bonds) have not been realized due to the reluctance of alkyl halides to undergo oxidative addition and the fast rate of β-hydride elimination of Pd-alkyl species. 18 However, recent breakthroughs in photoredox chemistry, [19][20][21] have shown that photoexcited palladium catalysts can be used to generate open-shell species from alkyl halide precursors.…”

“…However, it was uncertain at the outset of our studies whether NHP esters could be used as bifunctional reagents (both radical precursor and nucleophile) in this approach, 36,37 or if the stereo-and regioselectivity of the diene difunctionalization could be controlled in such a radical process. 15 Herein, we present the generation of -allylpalladium complexes through a radical approach mediated by visible light. The synthetic potential of this strategy was demonstrated through the 1,4-aminoalkylation of dienes (Fig.…”

Dearomative 1,4-difunctionalization of naphthalenes via palladium-catalyzed tandem Heck/Suzuki coupling reaction

“…Moreover, a Pd/C-catalyzed hydrogenation of alkene with H 2 balloon led to saturated spirocarbocycle 17 in 92% yield. It is noted that compounds 3a, 16, and 17 are analogs of a patented bioactive molecule for treating pain 56 , which indicates further potential application of the present method.…”

“…In this context, domino transformations involving initial carbometalation of simple alkenes or conjugated dienes and subsequent capture of the in situ generated σ-alkylmetal or π-allyl-metal species has been intensely developed for this purpose (Fig. 1a) [10][11][12][13][14][15][16] . On the other hand, as disclosed recently by the groups of Lautens [17][18][19][20] , Liang 21 , Yin 22,23 , Zhou 24 , Wu 25 , and us [26][27][28][29][30] , the application of endocyclic C=C bonds of heteroarenes as non-classic olefins has enabled a number of efficient dearomative difunctionalization reactions of indoles and furans with Pd-or Ni-catalyst 31 .…”