Diastereodivergent Hydrosilylative Enyne Cyclization Catalyzed by N‐Heterocyclic Carbene‐Ni(0)^†

Abstract

N-Heterocyclic carbenes | Enynes | Diastereodivergent synthesis | Hydrosilylation | HydroalkenylationCatalytic diastereodivergent hydrosilylative enyne cyclization with high generality and broad scope was achieved using electronic activated N-heterocyclic carbene-Ni(0) as a catalyst and R 3 SiH as silane (IPr Cl , syn-: anti-selectivity from up to 98 : 2 to 7 : 93 by Z = O, NH vs. NMs, R 1 = n-pentyl). Heterocycles bearing homoallylsilane rather than vinylsilane was obtained chemoselectively. The undesired yet highly competitive reactivity was suppressed, like direct hydrosilylation of alkene and alkyne concurrently. Optionally, the homoallylsilane products could be reduced further in one-pot using IPrMe as ligand and (EtO) 3 SiH as silane under otherwise the same standard condition as the above, offering practical access to additional stereocenters and more diverse product structures from enynes.

(NHC)Ni(II)-Directed Insertions and Higher Substituted Olefin Synthesis from Simple Olefins

“…The highly chemoselective insertion into NiCsp 3 was attributed to using a terminal enyne with an aldehyde like the others . However, similar selectivity was observed in both reductive hydroalkenylation and hydrosilylative enyne cyclization using the same sets of enynes (Figure A,C), suggesting that the result is due to the longer NiCsp 3 bond. This means that the basis of this selective ring-opening insertion is different from the Co-catalyzed regiodivergent HA of 1,6-enynes using acrylates and simple olefins .…”

Selective Access to Silacyclopentanes and Homoallylsilanes by La-Catalyzed Hydrosilylations of 1-Aryl Methylenecyclopropanes

“… It was found that the lanthanum and samarium ate complexes 1 and 2 both enabled chemo- and regioselective hydrosilylation to give silacyclopentane 8a in 88 and 81% yields, respectively, at room temperature in 24 h (entries 1 and 2) . In contrast, the Gd and Y ate complexes ( 3 and 4 , entries 3 and 4) and neutral lanthanum amide LLa­(N­(SiMe 3 ) 2 )­(THF) ( 5 , entry 5) gave homoallylsilane 8a′ as the major product and silacyclopentane 8a as a byproduct . For comparison, homoleptic La­(N­(SiMe 3 ) 2 ) 3 ( LaN 3 , entry 6) exhibited very low activity with a less than 5% yield.…”

Cobalt-Catalyzed Cyclization/Hydrosilylation Reaction of 1,6-Diynes Enabled by an Oxidative Cyclization–Hydrosilylation Mechanism

“…Intrigued by the economical and environmentally benign feature of late 3d metals, there has been great interest in late 3d metal-catalyzed cyclization/hydrosilylation reactions in recent years. The efforts have led to the development of late 3d metal-catalyzed cyclization/hydrosilylation reactions of enynes. − In contrast, progress in the cyclization and hydrosilylation of diynes is virtually unknown. To our knowledge, Tamao’s Ni-catalyzed reaction of 1,7-diynes with hydrosilanes, which furnishes six-membered ring-fused silyl dienes, is the sole example of the type (Scheme b). , The Ni-based catalytic system shows broad scope on hydrosilanes but is inapplicable to the cyclization/hydrosilylation of 1,6-diynes (Scheme b).…”