Cross-Coupling of Alkynes Catalyzed by Phebox−Rhodium Acetate Complexes

Cross-coupling between terminal alkynes and dimethyl acetylenedicarboxylate (3) in the presence of
1 mol % bis(oxazolinyl)phenyl−rhodium acetate complex, (Phebox-R)Rh(OAc)2(H2O) (1-ip, R = iPr),
under 1 atm hydrogen atmosphere furnished alkynyl-substituted maleic acid dimethyl esters with high
Z-selectivity. Rh−acetylide complexes (Phebox-R)Rh(OAc)(−C⋮CPh) (5-ip, R = iPr; 5-dm, R = Me2)
were isolated on the reactions of 1-ip and 1-dm with phenylacetylene. Reactions of 5-ip and 5-dm with
3 provide the corresponding vinyl complexes (Phebox-R)Rh(OAc)(−C(CO2Me)C(CO2Me)C⋮CPh) (6-ip, R = iPr; 6-dm, R = Me2) with E-configuration. Further reaction of 6-ip with phenylacetylene resulted
in the formation of an enyene 4a accompanied by the formation of 5-ip. The molecular structures of
5-dm and 6-dm were determined by X-ray diffraction.

在1 mol%的双(噁唑啉基)苯基乙酸铑配合物（bis(oxazolinyl)phenyl rhodium acetate complex）(Phebox-R)Rh(OAc)₂(H₂O)（1-ip，R = iPr）存在下，于1个大气压氢气氛围中，端炔烃（terminal alkynes）与乙炔二甲酸二甲酯(3)发生交叉偶联反应，以高Z选择性（Z-selectivity）得到炔基取代的马来酸二甲酯。将1-ip和1-dm分别与苯乙炔反应，可分离得到铑炔基配合物（Rh−acetylide complexes）(Phebox-R)Rh(OAc)(−C≡CPh)（5-ip，R = iPr；5-dm，R = Me₂）。5-ip和5-dm与(3)反应，生成相应的E构型（E-configuration）乙烯基配合物(Phebox-R)Rh(OAc)(−C(CO₂Me)=C(CO₂Me)C≡CPh)（6-ip，R = iPr；6-dm，R = Me₂）。6-ip与苯乙炔进一步反应，生成烯炔（enyene）4a，同时再生出5-ip。通过X射线衍射（X-ray diffraction）测定了5-dm和6-dm的分子结构。