Additive- and Ligand-Free Cross-Coupling Reactions between Alkenes and Alkynes by Iridium Catalysis

Abstract

Although a range of transition-metal-catalyzed cross-coupling reactions of alkenes and alkynes have been developed to produce valuable conjugated dienes, extension of these reactions to iridium catalysis has yet to be demonstrated. The first iridium-catalyzed alkene−alkyne cross-coupling reactions have been realized under ligand-and additive-free conditions. A wide range of acrylamides and alkynes could be used as coupling partners, providing branched (Z,Z)butadiene skeletons with excellent site-and stereoselectivities. The utility of this approach is also demonstrated by preparative-scale and C−H functionalization of perillic and artemisic amides.

Geminal group-directed olefinic C-H functionalization via four- to eight-membered exo-metallocycles

“…While the formation of four-membered metallocycle is highly challenging, seven- and eight-membered cyclometallation are also much less favored in general as the aliphatic carbon between the alkenyl motif and the coordinating group rotates freely and increases the entropic barrier significantly 9,14 . In line with our ongoing interest in olefinic C–H activation 19,34 , herein, we focus on gem -olefinic C-H activation via four- to eight-membered exo -cyclometallation, and the utility is characterized by the C–H functionalization of a wide range of functionalized alkenes, including synthetically valuable homoallyl-, bishomoallyl- and allyl alcohols/carbamates/amides that constitute integral structural motifs in natural products and drug design (Fig. 1d, e).…”

“…Remarkable efforts have been made in the vicinal group-directed olefinic C-H bond functionalization such as alkenylation 17–19 , alkynylation 20–22 , alkylation 23,24 , and others 25–34 . However, their applicability can be severely curtailed by vicinal selectivity displayed through the only 5- or 6-membered endo -metallocycles, and by the biased electronic and steric properties of the alkene substrates (Fig.…”

A palladium catalyzed stereo-convergent aminocarbonylation of 1,3-dienes with nitroarenes: synthesis of (E,E)-dienamides

“…5 Multistep synthesis is usually needed for these reactions. Recently, significant progress has been made in the transition-metal-catalyzed direct cross-coupling of acrylamides with alkenes 6 or alkynes 7 through the activation of the alkenyl C–H bond due to its atom- and step-economy (Scheme 1a). Despite important advances, these methods usually suffer from a limited substrate scope, especially the amide segments.…”

Palladium-Catalyzed Regio- and Diastereoselective Olefinic C–H Difluoromethylthiolation at Room Temperature

“…In the experiments carried out with 1a in the presence of radical scavengers, such as (2,2,6,6-tetramethylpiperidin-1-yl)­oxyl (TEMPO) and butylated hydroxytoluene (BHT), no obvious yield decrease was observed, indicating that the radical pathway in this catalytic process could be ruled out (Scheme a). Furthermore, the competition experiment with a different electronic substituent reveals that the reaction prefers the electron-donating group (Scheme b), thereby exhibiting an electrophilic C–H activation process . Treatment of acrylamides 1a under standard conditions, in the presence of D 2 O (20 equiv) without 2a , led to Z -selective H/D exchange on acrylamide (62% D), which exhibited a reversible cyclometalation event (Scheme c).…”