Catalytic Multisite-Selective Acetoxylation Reactions at sp² vs sp³ C–H Bonds in Cyclic Olefins

Abstract

The first Pd-catalyzed multisite-selective acetoxylation reactions are disclosed at an unactivated alkene sp C-H bond versus secondary allylic sp C-H bond in cyclic olefins via the modulation of directing groups. The different directing groups overcome the key challenge in differentiating C-H bonds and provide a new controlling approach for site-specific C-H activation. A wide variety of substrates are readily acetoxylated under operationally simple conditions. Mechanistic studies suggest that different Pd (IV) intermediates were involved in the multisite-selective acetoxylation reactions.

Synthesis of Spiro-dihydroquinoline and Octahydrophenanthrene Derivatives via Palladium-Catalyzed Intramolecular Oxidative Arylation

“…6 Accordingly, it is highly desirable to synthesize new compounds possessing these substructure moieties for drug discovery. To continue our research in palladium-catalyzed C−H activation, 7 herein we report the development of an intramolecular Fujiwara− Moritani/oxidative Heck cyclization to synthesize spirodihydroquinoline and octahydrophenanthrene derivatives employing the same palladium catalytic system.…”

Pd-Catalyzed Remote Site-Selective and Stereoselective C(Alkenyl)–H Alkenylation of Unactivated Cycloalkenes

“…Also, copper-free conditions led to the moderate yield (entry 3), which demonstrated that Cu­(OAc) 2 ·H 2 O as an oxidant can effectively regenerate the Pd­(II) catalyst from Pd(0). Moreover, PhI­(OAc) 2 serving as an oxidant in the Pd­(II)/Pd­(IV) catalytic cycle greatly reduced the yield (entry 4), which demonstrated that this reaction differentiating from previous research could prefer a Pd(0)/Pd­(II) catalytic cycle. Additionally, removal of base or using acids such as HOAc and PivOH, which can boost the palladium catalysis, , showed unsatisfactory results (entries 5–7).…”

“…Loh et al and Bi et al reported alkylation of γ-C­(alkenyl)–H, and Engle et al recently published elegant alkenylation of β or γ-C­(alkenyl)–H, utilizing different bidentate auxiliaries (Scheme A) . Notably, picolinamide (PA) as a removable directing group facilitated remote site-selective functionalization of the C­(alkenyl)–H bond such as arylation at the γ-position, alkenylation and iodination at the δ-position at a distance of three methylenes from PA, and acetoxylation at the δ-position (Scheme B). − However, only E -selective δ-C­(alkenyl)–H alkenylation of aminoethyl cycloalkenes with PA as a remote bidentate directing group has not been documented. Thus, inspired by the above literature and previous work, , we report an efficient method for the synthesis of cycle-containing dienes starting from cycloalkenes bearing PA and electron-deficient alkenes to generate corresponding only E -products (Scheme C).…”

Diastereoselective palladium-catalyzed functionalization of prochiral C(sp3)–H bonds of aliphatic and alicyclic compounds

“…The protocol of diastereoselective Pd( ii )-catalyzed, DG-aided C–H functionalization has been extended to assemble cis olefins via Z selective C(sp 2 )–H-functionalization. 5,86,87 Babu reported 86 a the diastereoselective Pd( ii )-catalyzed, AQ-aided β-C(sp 2 )–H arylation of acrylamide 72a with ArI to afford the Z -cinnamamide 72b 86 a , b (Scheme 37). Xu/Loh and Besset have demonstrated the Z selective β-C(sp 2 )–H alkylation, 86 c and chlorination 86 e of substrate 72a to afford the corresponding products 72k and 72l .…”