Synthesis of Silylboronic Esters Functionalized on Silicon
摘要:
New silylpinacolboranes bearing chloro, fluoro, alkoxy, and dialkylamino groups on silicon were synthesized in high yields via derivatization of [(diethylamino)diphenylsilyl]pinacolborane, which was prepared by reaction of [(diethylamino)diphenylsilyl]lithium with (isopropoxy)pinacolborane, and (chlorodimethylsilyl)pinacolborane, prepared by reaction of (dimethylphenylsilyl)pinacolborane with hydrogen chloride in the presence of a catalytic amount of aluminum chloride.
Silylpinacolboranes bearing dialkylamino groups on the silicon atom several as synthetic equivalents of silylene in palladium-catalyzed reactions with terminal alkynes, leading to the formation of 2, 4-disubstituted siloles in high yield. It was found that the amino group on the silicon atom was critically important for the reaction; no silole products were found in reactions using silylpinacolboranes carrying aryl, chloro, or alkoxy groups on the silicon atoms. Site-selective bromination of 1,1-dimethyl-2,4-diphenylsilole followed by Migita-Kasugi-Stille coupling with (arylalkynyl)tributylstannanes gave novel Pi-conjugated siloles with good total yields.