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Our Voyage from Catalytic Cross-Hydroalkenylation to Transfer-Dehydroaromatization of Cyclic -Systems: Reactivity and Selectivity Changes Enabled by NHC-Ni and NHC-Pd Hydride Equivalents Subsequently, we found that the (NHC)Pd-H catalyst could be generated analogously according to a reported procedure using silane and CataXium A ligated palladium chloride, [98] which was used as an olefin isomerization catalyst (Scheme 13). Only a few examples with limited isomerization problems are reported under harsh conditions (under 50 equiv. cyclic olefin) by P-based systems..[71] Presumably, the problem is related to the high olefin isomerization ability of the P-M-H (e.g., M = Ni or Pd). Keywords: hydroalkenylation; transfer-hydrogenation; dehydroaromatization; N-heterocyclic carbenes; nickel; palladium EN hydroalkenylation transfer-hydrogenation dehydroaromatization N-heterocyclic carbenes nickel palladium 1639 1654 16 08/18/23 20230901 NES 230901 Graph 1 Introduction Transition-metal hydrides (M-H) are important catalysts or intermediates in organic transformations such as catalytic olefin polymerization/oligomerization, [1] allylic CH activation, [2] isomerization, [5] and cross-hydroalkenylation (HA) of olefins (Scheme 1). [Extracted from the article]

Abstract: Cross‐hydroalkenylation of a vinyl ether (1) with an α‐olefin (2) was first achieved by a set of [NHC‐Ni(allyl)]BArF (NHC=N‐heterocyclic carbene) catalysts. Both 1,2‐ and 1,3‐disubstituted allyl ethers were obtained, highly selectively, by using NHCs of different sizes. In contrast, the chemoselectivity (i.e., 1 as acceptor and 2 as donor) was controlled mostly by electronic effects through the catalyst–substrate interaction. Sterically bulkier alkenes (2) were used as preferred donors compared to smaller alkenes. This electronic effect also served as a basis for the first tail‐to‐head cross‐hydroalkenylations of 1 with either a vinyl silane or boronic ester. [ABSTRACT FROM AUTHOR]

Highly selective cross-hydroalkenylations of endocyclic 1,3-dienes at the least substituted site with α-olefins were achieved with a set of neutral (NHC)NiIIH(OTf) catalysts and cationic NiII catalysts with a novel NHC ligand. Under heteroatom assistance, skipped dienes were obtained in good yields, often from equal amounts of the two substrates and at a catalyst loading of 2-5 mol %. Rare 4,3-product selectivity (i.e., with the H atom at C4 and the alkenyl group at C3 of the diene) was observed, which is different from the selectivity of known dimerizations of α-olefins with both acyclic Co and Fe systems. The influence of the various substituents on the NHC, 1,3-diene, and α-olefin on the chemo-, regio-, and diastereoselectivity was studied. High levels of chirality transfer were observed with chiral cyclohexadiene derivatives. [ABSTRACT FROM AUTHOR]