Palladium(O)-catalyzed alkylation of various allylic carbonates by aromatic thiols allowed the easy preparation of various allylic aryl sulphides in quite good yields. The reaction was regioselective with substitution at the less hindered side of the π-allyl system whatever the temperature of the reaction, and was diastereoselective with net retention of configuration.
Stereochemistry of the palladium-catalyzed allylic substitution: the syn-anti dichotomy in the formation of (π-allyl)palladium complexes and their equilibration
作者:Ivo Starý、Jaroslav Zajíček、Pavel Kočovský
DOI:10.1016/s0040-4020(01)88263-6
日期:1992.1
The mechanism of palladium(0)-catalyzed allylicsubstitution has been investigated with the aim of finding whether or not the intermediate (π-allyl)palladiumcomplexes can arise in a syn fashion as an alternative to the well known anti-mechanism. Using (diphenylphosphino)acetate as a leaving group and stereochemically biased substrates 30b and 35b evidence for the syn stereochemistry has been acquired
Nickel-catalysed substitution reactions of allylic carbonates with aryl- and alkenyl-borates
作者:Yuichi Kobayashi、Eitatsu Ikeda
DOI:10.1039/c39940001789
日期:——
Substitution reactions of 1,3-disubstituted allylic carbonates 3 with aryl- and alkenyl-borates 4 are catalysed by [NiCl2(dppf)][dppf = 1,1′-bis(diphenylphosphino)ferrocene], and in the case of the cyclic carbonate 7, the reaction proceeds with complete inversion.
Kobayashi Yuichi, Ikeda Eitatsu, J. Chem. Soc. Chem. Commun, (1994) N 15, S 1789- 1790
作者:Kobayashi Yuichi, Ikeda Eitatsu
DOI:——
日期:——
Nickel-Catalyzed Coupling Reaction of 1,3-Disubstituted Secondary Allylic Carbonates and Lithium Aryl- and Alkenylborates
作者:Yuichi Kobayashi、Ryo Mizojiri、Eitatsu Ikeda
DOI:10.1021/jo960458c
日期:1996.1.1
This account describes coupling reaction of 1,3-disubstituted secondary allylic carbonates with lithium aryl- and alkenylborates in the presence of a nickel. catalyst. Berates examined are 4, 5, and 6, and reactivity and selectivity were investigated using the allylic carbonates la and Ib. Coupling of la,b with berates 4 was effected with the nickel catalyst, NiCl2(PPh(3))(2) or NiCl2(dppf), in THF at 45-65 degrees 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 la,b after transformation to berates 5 with MeLi. Though coupling using 4 and 5 required elevated temperature (45-65 degrees C), cyclic berates 6 prepared in situ from boronates 8 and MeLi were found to couple with la,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) . CHCl3 + 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 pi-allylnickel intermediates.