Nickel Catalyzed Coupling Reaction of Allylic Carbonates with Vinylic Borates Derived from Acetylenes via Hydroboration

Kobayashi, Yuichi; Mizojiri, Ryo; Ikeda, Eitatsu

doi:10.1055/s-1995-5287

Cited by 13 publications

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“…Since higher temperatures (45−65 °C) are needed, we have continued this investigation and discovered that borates 6 derived from cyclic boronates 8 and MeLi (eq 4) are more reactive reagents , and the reaction proceeds at room temperature or below. In this paper we describe a full account of these new reagent/catalyst systems …”

Section: Introductionmentioning

confidence: 99%

Nickel-Catalyzed Coupling Reaction of 1,3-Disubstituted Secondary Allylic Carbonates and Lithium Aryl- and Alkenylborates

1996

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This account describes coupling reaction of 1,3-disubstituted secondary allylic carbonates with lithium aryl-and alkenylborates in the presence of a nickel catalyst. Borates examined are 4, 5, and 6, and reactivity and selectivity were investigated using the allylic carbonates 1a and 1b. Coupling of 1a,b with borates 4 was effected with the nickel catalyst, NiCl 2 (PPh 3 ) 2 or NiCl 2 (dppf), in THF at 45-65°C to provide products 3 in good yields with almost 100% regio-and stereoselectivities. Trivalent organoboranes prepared from acetylenes by hydroboration with catecholborane also underwent coupling reaction with 1a,b after transformation to borates 5 with MeLi. Though coupling using 4 and 5 required elevated temperature (45-65°C), cyclic borates 6 prepared in situ from boronates 8 and MeLi were found to couple with 1a,b at room temperature or below. Regio-and stereoselectivities were almost 100% as were observed in the cases of 4 and 5. In these reactions, palladium complexes such as Pd(PPh 3 ) 4 , Pd 2 (dba) 3 ‚CHCl 3 + 2 PPh 3 showed no catalytic activity. Stereochemical aspect of the present reaction was studied using cyclohexenyl carbonate 24 with 2-furylborate 4e and phenylborate 6a, and was found to proceed with overall anti fashion. With additional experiments, the mechanism of the present reaction was discussed in terms of transient π-allylnickel intermediates.

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Section: Introductionmentioning

confidence: 99%