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[摘要]：Described herein is an operationally simple and mild method for the stereospecific synthesis of internal conjugated (Z)-enynyltrimethylsilanes whose conjugation is extended away from the distal alkynyl carbon atom. This protocol involves two types of cross-coupling reaction, a Suzuki-type reaction and a sila-Sonogashira reaction, and the desired synthesis can be performed in a one-pot manner. Thus, the copper-mediated cross-coupling reaction of dicyclohexyl[(Z)-1-(trimethylsilyl)alk-1-enyl]boranes with (trimethylsilyl)ethynyl bromide is carried out in the presence of aq. lithium hydroxide at -15 癈 to room temp., resulting in the stereospecific formation of (Z)-1,3-bis(trimethylsilyl)alk-3-en-1-ynes. Subsequent reaction is allowed to proceed without isolation of the enynes. Thus, palladium/copper-catalyzed cross-coupling reactions with aryl iodides, cycloalk-1-enyl triflates, and (E)- and (Z)-alk-1-enyl iodides can be accomplished in the presence of either 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or tetrabutylammonium fluoride (TBAF) at ambient temp. to provide the corresponding internal conjugated (Z)-enynyltrimethylsilanes possessing one more sp-sp2 carbon bond. |
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