Boryl substitution of functionalized aryl-, heteroaryl- and alkenyl halides with silylborane and an alkoxy base: expanded scope and mechanistic studies
作者:Eiji Yamamoto、Satoshi Ukigai、Hajime Ito
DOI:10.1039/c5sc00384a
日期:——
A transition-metal-free method has been developed for the boryl substitution of functionalized aryl-, heteroaryl- and alkenyl halides using a silylborane/alkoxy-base reagent. Borylation of (Z)-alkenyl halides proceeded in a stereoretentive manner.
Condensation of halo-substituted 1,3-azoles (1,3-oxazoles, 1,3-thiazoles and imidazoles) with phenylsulfonylacetonitrile under basic conditions was promoted by catalytic action of tetrakis(triphenylphosphine)palladium(0) to give α-phenylsulfonyl-1,3-azoleacetonitriles. The adaptability of halogen atoms for the cross-coupling reaction was investigated. The reaction of 4-halo-1,2-azoles was also examined.
A reaction sequence involving halogenation and replacement of the halo substituent by a nitro group using dinitrogen tetraoxide has led to a general, convenient route to 5-nitrooxazoles. Reaction schemes employing both bromine and iodine as the halo substituent have been investigated; however, the method using iodine preceded by a mercuration step affords a better overall yield in the range of 20–50%