Intermolecular trans-bis-silylation of terminal alkynes

Addition of interelement compounds across alkynes is a straightforward strategy for the synthesis of densely functionalized alkenes, which are versatile units in numerous biologically active compounds. Of these processes the bis-silylation of alkynes is of particular interest, due to the synthetic use of the alkenyl silane reaction products. While cis-bis-silylation of alkynes is well known, trans-bis-silyation of alkynes is relatively underdeveloped. Here, we report the intermolecular trans-bis-silylation of terminal alkynes, using Pd-catalysis and disilane reagent 8-(2-substituted-1,1,2,2-tetramethyldisilanyl)quinoline (TMDQ), to selectively form trans-bis-silylated alkenes. The reaction process was found to be compatible with aryl and alkyl alkynes as well as those bearing electron-withdrawing groups and other alkenyl or alkynyl functionalities. The use of the reaction was displayed through late-stage functionalization of terminal alkynes bearing natural product or drug motifs and onward synthetic transformations of the trans-bis-silylated alkenes reaction products. Experimental and computational mechanistic studies reveal that the reaction probably proceeds through a combined cis-bis-silylation and Z/E isomerization process and that the use of TMDQ as the limiting reagent is key to the desired reactivity.