Palladium-Catalyzed Alkynylation of Enones with Alkynylsilanes via C–C Bond Activation

Abstract

We report herein the synthesis of 1,3-enynes via palladium-catalyzed cross-coupling between enone derivatives and alkynylsilanes. The employment of an appropriate pyridine-oxazoline ligand is the key to the C−C cleavage and the high E/Z stereoselectivity. This protocol features broad substrate scope and wide functional-group tolerance, affording the desired products in moderate-to-good yields. Late-stage diversification of natural product β-ionone further demonstrated the synthetic utility of this protocol.

Total Synthesis of Syringin and Its Natural Analogues via C—C Bond Activation of Aryl Ketones†

“…Encouraged by our previous arylation, alkenylation, alkylation, borylation, and silylation of aryl ketone, [ 57‐68 ] we next began to explore these protocols to synthesize the syringin analogues (Scheme 4). Aryl boron reagents bearing ‐t ‐Bu, ‐Me and ‐OMe gave the desired products 4a—4c in moderate yields.…”

“…[ 55‐56 ] Recently, our group reported the palladium‐catalyzed ligand‐promoted C(O)–C bond cleavage of unstrained aryl ketones (Scheme 1b). [ 57‐68 ] Considering the broad biological activites of syringin, herein, we present our achievement in the total synthesis of syringin, in which palladium‐catalyzed C(O)–C bond functionalization of cheap acetosyringone supported the key transformations (Scheme 1c). Furthermore, various syringin analogues bearing alkynyl, alkenyl, aryl, alkyl, siliconyl, and boronyl groups were also constructed via the aryl palladium intermediate.…”

Density Functional Theory Study on the Mechanism of Nickel-Catalyzed 3,3-Dialkynylation of 2-Aryl Acrylamides Via Double Vinylic C–H Bond Activation

“…Olefinic C­(sp 2 )–H alkynylation has been an active area of research in the past decade for the flexibility of introducing complex groups and constructing novel compounds. − In the past decades, much progress has been achieved in the direct olefinic C­(sp 2 )–H alkynylation using noble transition metals such as Pd, − Rh, − Ru, and Au, and the participation of chelation-assisted systems with N , N -bidentate directing groups has been an ideal approach to achieve site-selective C–H bond functionalization. − Recently, the development of direct C–H alkynylation catalyzed by 3d transition metals to construct C­(sp 2 )–C­(sp) bonds has been a promising direction because of their low price and lower toxicity. For instance, in 2015, Yi et al reported a nickel-catalyzed C–H alkynylation reaction between two kinds of inactivated C­(sp 2 )–H and triisopropylsilyl (TIPS)-substituted bromoalkyne, which is the first report on Ni-catalyzed C­(sp 2 )–C­(sp) bond formation via 8-quinolinyl-chelation assistance .…”

The Regio- and Stereoselective Synthesis of 1,4-Diarylbut-1-en-3-ynes Having Aryl Groups at the Mutual Syn Positions

“…General methods for the synthesis of conjugated 1,4-diarylenynes, where the substituents in the 1-and 4-positions are different. The available procedures include cross-coupling reactions, (i.e., Suzuki [17], Stille [18], Hiyama-Denmark [19], Sonogashira [20][21][22][23][24], Heck [25]) (A), Kumada [26], and Suzuki [27] (B), the hydroarylation of 1,3-diynes [28,29] (C), the hydroalkynylation of alkynes and/or allenes (D) [30,31], and a few less general procedures [32][33][34][35].…”