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.
Palladium-catalysed cis- and trans-silaboration of terminal alkynes has been developed via the addition of (chlorodimethylsilyl)pinacolborane, followed by a one-pot conversion of the chloro group on the silicon atom to an isopropoxy group.
esters to terminalalkynes can be switched by the choice of phosphorus ligands on the palladium catalysts. The silaboration proceeds with normal regioselectivity in the presence of (eta(3)-C(3)H(5))Pd(PPh(3))Cl (1.0 mol %) to give 1-boryl-2-silyl-1-alkenes in high yields. In sharp contrast, selective formation of the inverse regioisomers, 2-boryl-1-silyl-1-alkenes, takes place when the reaction is carried
Silaborative Carbocyclizations of 1,7-Enynes. Diastereoselective Preparation of Chromane Derivatives
作者:You-Cai Xiao、Christina Moberg
DOI:10.1021/acs.orglett.5b03479
日期:2016.1.15
Palladium(0)-catalyzed carbocyclization of 1,7-enynes mediated by (chlorodimethylsilyl)pinacolborane proceeds with 1,8-addition of the silicon and boron functions to give functionalized cyclohexane derivatives with boron attached to the exocyclic olefin. A variety of chromane dervatives are accessible by this method. In contrast to the analogous reactions with 1,6-enynes, the configuration of the newly
Regioselective Preparation of Functionalized exo-Methylene- cyclopentanes and exo-Methylenepyrrolidines via Silaborative Carbocyclization of 1,6-Enynes
The vinylboronate functions were employed in palladium-catalyzed Suzuki cross-coupling reactions with a range of aryl bromides, containing electron-withdrawing as well as electron-donating substituents, furnishing arylated exo-methylenecyclopentanes or exo-methylenepyrrolidines in good yields. Subsequent oxidation of the isopropoxydimethylsilyl function generated via addition of (chlorodimethylsilyl)pinacolborane
Palladium-catalyzed silaboration of 1,3-enynes followed by Suzuki–Miyaura coupling with alkenyl iodides and Hiyama coupling with aryl iodides provides access to 1,3,5-trienes with defined regio- and stereochemistry.