Synthesis of (Z)-1-aryl-2-(germyl)-1-(stannyl)ethenes and the related ethenes, precursors to stereodefined germylethenes, via Pd(dba)2–P(OCH2)3CEt-catalyzed germastannation of acetylenes in THF

Synthesis of novel stereodefined vinylgermanes bearing an allyl group or an allenyl group: (E)‐2‐aryl‐1‐germylalka‐1,4‐dienes and (E)‐4‐aryl‐5‐germylpenta‐1,2,4‐trienes

“…NMR analysis of the product disclosed that the vinyl proton α to the germyl group appeared at 6.02 ppm, which is at somewhat higher field than that of the starting (Z)-germyl(stannyl)ethene 1a (δ = 6.63 ppm). 21,22 However, the chemical shift of the vinylic proton of 2a (δ = 6.02 ppm) was very close to that of its silicon analog, (E)-1-(trimethylsilyl)-2-phenylpenta-1,4-diene (E)-2a-Si (δ = 5.97 ppm). 24,45 On the other hand, the vinyl proton α to Si in (Z)-2a-Si has been reported to appear at 5.59 ppm.…”

“…The chemical shift of the vinyl proton α to the germyl group in all products appeared in the range 6.22-5.58 ppm ( Table 2). Other germyl(stannyl)ethenes such as (Z)-2-(tri-nbutylstannyl)-1-(triethylgermyl)-2-(2-thienyl)ethene 1l 22 and (Z)-3-(tri-n-butylstannyl)-4-(triethylgermyl)-2-methylbut-3-en-2-ol 1m 22 were also subjected to the destannylative allylation under similar conditions producing the respective (E)-1-germyl-2-substituted penta-1,4-dienes 2l and 2m exclusively with good isolated yields (Schemes 4 and 5). In the latter case, it should be emphasized that the hydroxy group tolerated the coupling reaction.…”

Acid‐dependent selective formation of trans‐aryl(germyl)ethenes or 1‐aryl‐1‐germylethenes by the protodestannylation of (Z)‐germyl(stannyl)ethenes

“…1,2 The catalysis completes the reaction with a shorter reaction time than the previously reported Pd(PPh 3 ) 4 -catalyzed germastannation and gives the (Z)-1-aryl-2-germyl-1-stannylethenes 1 3,4 in much higher yields. The resulting products, 1, are potentially useful compounds, because they may be transformed into a variety of organogermanium compounds via various reactions of the Migita-Kosugi-Stille type.…”

“…stannane in the presence of a Pd(dba) 2 -EPBO combination catalyst. Several new adducts of 1 were synthesized in this stage, and their spectral data are shown in the Experimental section.…”

“…Recently, we reported that a combination of Pd(dba) 2 and EPBO (EPBO: 4-ethyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane) effected the germastannation of arylacetylenes using tributyl(triethylgermyl)stannane. 1,2 The catalysis completes the reaction with a shorter reaction time than the previously reported Pd(PPh 3 ) 4 -catalyzed germastannation and gives the (Z)-1-aryl-2-germyl-1-stannylethenes 1 3,4 in much higher yields.…”