Modification of the Fritsch–Buttenberg–Wiechell rearrangement: a facile route to unsymmetrical butadiynes
作者:Erin T Chernick、Sara Eisler、Rik R Tykwinski
DOI:10.1016/s0040-4039(01)01901-3
日期:2001.12
echell rearrangement has been used to form unsymmetrically substituted 1,3-butadiynes from 1,1-dibromo-olefin precursors. The reaction proceeds via lithium–halogen exchange, followed by migration of the aryl or alkynyl moiety to provide the butadiyne framework. The facile formation of the dibromo-olefins in three steps from commercially available aryl aldehydes or carboxylic acid chlorides makes this
Chemoselective Cobalt(I)-Catalyzed Cyclotrimerization of (Un)Symmetrical 1,3-Butadiynes for the Synthesis of 1,2,4-Regioisomers
作者:Sebastian M. Weber、Gerhard Hilt
DOI:10.1021/acs.orglett.9b01281
日期:2019.6.7
The cobalt(I)-catalyzed cyclotrimerization of (un)symmetrical 1,4-disubstituted 1,3-butadiynes is presented. In the case of unsymmetrical 1,3-butadiynes, this reaction can generate eight 1,2,4-substituted and four 1,3,5-substituted isomers. A single 1,2,4-substituted isomer was formed in excellent yields (up to 99%) and exclusive regioselectivities (>99:1) when symmetrical or a 1,3-butadiyne with an
Control of the Regioselectivity in Cobalt- versus Ruthenium-Catalyzed Alder-ene Reaction of Unsymmetrical 1,3-Diynes
作者:Sebastian M. Weber、Gerhard Hilt
DOI:10.1021/acs.orglett.6b03729
日期:2017.2.3
The Alder-enereaction of trialkylsilyl-substituted 1,3-butadiynes with terminal alkenes was investigated utilizing a cobalt-based catalyst, and the results were compared with Alder-ene rections catalyzed by the [CpRu(H3CCN)3]PF6 catalyst. Obviously, the two catalysts gave complementary results of yn-dienes differing in the site where the new carbon–carbon bond was formed. Of particular interest are
Cobalt-Catalyzed Regio- and Stereoselective Hydrosilylation of 1,3-Diynes To Access Silyl-Functionalized 1,3-Enynes
作者:Hui Leng Sang、Yongyi Hu、Shaozhong Ge
DOI:10.1021/acs.orglett.9b01836
日期:2019.7.5
A regio- and stereoselective hydrosilylation of 1,3-diynes has been developed relying on catalysts generated from bench-stable Co(acac)2 and dppp ligand. A variety of symmetrical and unsymmetrical 1,3-diynes undergo this transformation, yielding the corresponding silyl-functionalized 1,3-enynes in high yields with excellent regioselectivity. Gram-scale reactions and further transformations of the silyl-containing
Cobalt-Catalyzed Regiodivergent Stereoselective Hydroboration of 1,3-Diynes To Access Boryl-Functionalized Enynes
作者:Hui Leng Sang、Caizhi Wu、Guan Ge Darren Phua、Shaozhong Ge
DOI:10.1021/acscatal.9b03139
日期:2019.11.1
We report a regiodivergent and stereoselective hydroboration of 1,3-diynes with pinacolborane (HBpin) in the presence of cobalt catalysts generated in situ from bench-stable Co(acac)(2) and bisphosphine ligands. These cobalt catalysts were activated by the reactions with HBpin. A range of unsymmetrical and symmetrical 1,3-diynes reacted smoothly with HBpin in the presence of Co(acac)(2)/xantphos to selectively afford enynylboronate products with boron addition to the internal carbon of the 1,3-diyne unit. However, these 1,3-diynes reacted in the presence of Co(acac)(2)/dppf to form enynylboronate products with boron addition to the external carbon of the 1,3-diyne unit. These hydroboration reactions show good functional group compatibility and can be readily scaled up to gram-scales without using a drybox. Deuterium-labeling experiments suggest a cis-addition of HBpin to the less-hindered triple bond of 1,3-diynes. Furthermore, the comparison of the regioselectivity between cobalt-catalyzed hydrosilylation and hydroboration reactions of the same 1,3-diyne substrate suggests that Co(acac)(2)/xantphos-catalyzed regioselective 1,3-diyne hydroboration proceeds through a cobalt-hydride intermediate while Co(acac)(2)/dppf-catalyzed 1,3-diyne hydroboration proceed through a cobalt boryl intermediate.