%0 Journal Article %A Chen, Jinzhu %A Yu, Zhengkun %A Zheng, Zhaoyan %A Gu, Kaichun %A Wu, Sizhong %A Zeng, Fanlong %A Tan, Weiqiang %A Wu, Xiaowei %A Xiao, Wenjing %D 2005 %T Chemoselective Stepwise Demetalation of Unusually Stable Fischer Biscarbene Complexes by Domino [4+2]/[2+2] Cycloaddition of 2-Isopropenyl-2-oxazoline to 1-Alkynyl Fischer Carbene Complexes of Chromium and Tungsten %U https://acs.figshare.com/articles/journal_contribution/Chemoselective_Stepwise_Demetalation_of_Unusually_Stable_Fischer_Biscarbene_Complexes_by_Domino_4_2_2_2_Cycloaddition_of_2_Isopropenyl_2_oxazoline_to_1_Alkynyl_Fischer_Carbene_Complexes_of_Chromium_and_Tungsten/3304534 %R 10.1021/om049213d.s001 %2 https://acs.figshare.com/ndownloader/files/5142262 %K biscarbene complexes 3 %K Chemoselective Stepwise Demetalation %K core %K diester 7 %K cycloaddition %K monocarbene complexes 3 %K monocarbene complexes 6 %K CO %K Unusually Stable Fischer Biscarbene Complexes %K 5 b %K tricyclic %K Domino %X Domino [4+2]/[2+2] cycloaddition of 2-isopropenyl-2-oxazoline 2 to 1-alkynyl Fischer carbene complexes (CO)5MC(OEt)C⋮CPh 1 (a, M = Cr; b, W) in a 1:2 molar ratio afforded unusually stable biscarbene complexes 3a and 3b containing a novel four-, five-, and six-membered tricyclic core in 99.6% and 45.2% yields, respectively. Chain-opening β-aminoalkenyl monocarbene complex 4b and β-amidoalkenyl monocarbene complex 5b of tungsten were also isolated from the cycloaddition upon treatment of the reaction mixture of 1b and 2 on silica gel. Partial and full oxidation of 3a,b with pyridine N-oxide underwent efficient chemoselective stepwise demetalation to afford the corresponding monocarbene complexes 6a,b and organic diester 7, respectively, under mild conditions. The X-ray crystallographic study revealed the presence of a four-, five-, and six-membered tricyclic core in compounds 3, 6, and 7, and the methyl and oxazolindinyl groups derived from oxazoline 2 are positioned syn with respect to the azabicyclo[4.2.0]octadiene bicyclic moiety, which is oriented in the opposite direction. X-ray crystal structural data are reported for the bis- and monocarbene complexes 3a, 5b, and 6b as well as for diester 7. %I ACS Publications